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diff --git a/doc/gawk.info b/doc/gawk.info index aad73f7a..f1aa1f4a 100644 --- a/doc/gawk.info +++ b/doc/gawk.info @@ -20,16 +20,13 @@ implementation of AWK. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the -Invariant Sections being "GNU General Public License", the Front-Cover -texts being (a) (see below), and with the Back-Cover Texts being (b) -(see below). A copy of the license is included in the section entitled -"GNU Free Documentation License". +Invariant Sections being "GNU General Public License", with the +Front-Cover Texts being "A GNU Manual", and with the Back-Cover Texts +as in (a) below. A copy of the license is included in the section +entitled "GNU Free Documentation License". - a. "A GNU Manual" - - b. "You have the freedom to copy and modify this GNU manual. Buying - copies from the FSF supports it in developing GNU and promoting - software freedom." + a. The FSF's Back-Cover Text is: "You have the freedom to copy and + modify this GNU manual." File: gawk.info, Node: Top, Next: Foreword, Up: (dir) @@ -51,16 +48,13 @@ implementation of AWK. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the -Invariant Sections being "GNU General Public License", the Front-Cover -texts being (a) (see below), and with the Back-Cover Texts being (b) -(see below). A copy of the license is included in the section entitled -"GNU Free Documentation License". - - a. "A GNU Manual" +Invariant Sections being "GNU General Public License", with the +Front-Cover Texts being "A GNU Manual", and with the Back-Cover Texts +as in (a) below. A copy of the license is included in the section +entitled "GNU Free Documentation License". - b. "You have the freedom to copy and modify this GNU manual. Buying - copies from the FSF supports it in developing GNU and promoting - software freedom." + a. The FSF's Back-Cover Text is: "You have the freedom to copy and + modify this GNU manual." * Menu: @@ -126,8 +120,8 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) includes command-line syntax. * One-shot:: Running a short throwaway `awk' program. -* Read Terminal:: Using no input files (input from - terminal instead). +* Read Terminal:: Using no input files (input from the + keyboard instead). * Long:: Putting permanent `awk' programs in files. * Executable Scripts:: Making self-contained `awk' @@ -149,6 +143,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Other Features:: Other Features of `awk'. * When:: When to use `gawk' and when to use other things. +* Intro Summary:: Summary of the introduction. * Command Line:: How to run `awk'. * Options:: Command-line options and their meanings. @@ -170,16 +165,21 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) program. * Obsolete:: Obsolete Options and/or features. * Undocumented:: Undocumented Options and Features. +* Invoking Summary:: Invocation summary. * Regexp Usage:: How to Use Regular Expressions. * Escape Sequences:: How to write nonprinting characters. * Regexp Operators:: Regular Expression Operators. * Bracket Expressions:: What can go between `[...]'. -* GNU Regexp Operators:: Operators specific to GNU software. -* Case-sensitivity:: How to do case-insensitive matching. * Leftmost Longest:: How much text matches. * Computed Regexps:: Using Dynamic Regexps. +* GNU Regexp Operators:: Operators specific to GNU software. +* Case-sensitivity:: How to do case-insensitive matching. +* Regexp Summary:: Regular expressions summary. * Records:: Controlling how data is split into records. +* awk split records:: How standard `awk' splits + records. +* gawk split records:: How `gawk' splits records. * Fields:: An introduction to fields. * Nonconstant Fields:: Nonconstant Field Numbers. * Changing Fields:: Changing the Contents of a Field. @@ -190,7 +190,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Single Character Fields:: Making each character a separate field. * Command Line Field Separator:: Setting `FS' from the - command-line. + command line. * Full Line Fields:: Making the full line be a single field. * Field Splitting Summary:: Some final points and a summary table. @@ -216,8 +216,10 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) `getline'. * Getline Summary:: Summary of `getline' Variants. * Read Timeout:: Reading input with a timeout. -* Command line directories:: What happens if you put a directory on +* Command-line directories:: What happens if you put a directory on the command line. +* Input Summary:: Input summary. +* Input Exercises:: Exercises. * Print:: The `print' statement. * Print Examples:: Simple examples of `print' statements. @@ -241,6 +243,8 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Special Caveats:: Things to watch out for. * Close Files And Pipes:: Closing Input and Output Files and Pipes. +* Output Summary:: Output summary. +* Output Exercises:: Exercises. * Values:: Constants, Variables, and Regular Expressions. * Constants:: String, numeric and regexp constants. @@ -251,11 +255,14 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Variables:: Variables give names to values for later use. * Using Variables:: Using variables in your programs. -* Assignment Options:: Setting variables on the command-line +* Assignment Options:: Setting variables on the command line and a summary of command-line syntax. This is an advanced method of input. * Conversion:: The conversion of strings to numbers and vice versa. +* Strings And Numbers:: How `awk' Converts Between + Strings And Numbers. +* Locale influences conversions:: How the locale may affect conversions. * All Operators:: `gawk''s operators. * Arithmetic Ops:: Arithmetic operations (`+', `-', etc.) @@ -283,6 +290,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Function Calls:: A function call is an expression. * Precedence:: How various operators nest. * Locales:: How the locale affects things. +* Expressions Summary:: Expressions summary. * Pattern Overview:: What goes into a pattern. * Regexp Patterns:: Using regexps as patterns. * Expression Patterns:: Any expression can be used as a @@ -329,6 +337,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) gives you information. * ARGC and ARGV:: Ways to use `ARGC' and `ARGV'. +* Pattern Action Summary:: Patterns and Actions summary. * Array Basics:: The basics of arrays. * Array Intro:: Introduction to Arrays * Reference to Elements:: How to examine one element of an @@ -351,6 +360,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) `awk'. * Multiscanning:: Scanning multidimensional arrays. * Arrays of Arrays:: True multidimensional arrays. +* Arrays Summary:: Summary of arrays. * Built-in:: Summarizes the built-in functions. * Calling Built-in:: How to call built-in functions. * Numeric Functions:: Functions that work with numbers, @@ -385,6 +395,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) runtime. * Indirect Calls:: Choosing the function to call at runtime. +* Functions Summary:: Summary of functions. * Library Names:: How to best name private global variables in library functions. * General Functions:: Functions that are of general use. @@ -419,6 +430,8 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Group Functions:: Functions for getting group information. * Walking Arrays:: A function to walk arrays of arrays. +* Library Functions Summary:: Summary of library functions. +* Library Exercises:: Exercises. * Running Examples:: How to run these examples. * Clones:: Clones of common utilities. * Cut Program:: The `cut' utility. @@ -448,6 +461,8 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Anagram Program:: Finding anagrams from a dictionary. * Signature Program:: People do amazing things with too much time on their hands. +* Programs Summary:: Summary of programs. +* Programs Exercises:: Exercises. * Nondecimal Data:: Allowing nondecimal input data. * Array Sorting:: Facilities for controlling array traversal and sorting arrays. @@ -459,6 +474,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * TCP/IP Networking:: Using `gawk' for network programming. * Profiling:: Profiling your `awk' programs. +* Advanced Features Summary:: Summary of advanced features. * I18N and L10N:: Internationalization and Localization. * Explaining gettext:: How GNU `gettext' works. * Programmer i18n:: Features for the programmer. @@ -470,6 +486,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * I18N Example:: A simple i18n example. * Gawk I18N:: `gawk' is also internationalized. +* I18N Summary:: Summary of I18N stuff. * Debugging:: Introduction to `gawk' debugger. * Debugging Concepts:: Debugging in General. @@ -488,31 +505,23 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Miscellaneous Debugger Commands:: Miscellaneous Commands. * Readline Support:: Readline support. * Limitations:: Limitations and future plans. -* General Arithmetic:: An introduction to computer - arithmetic. -* Floating Point Issues:: Stuff to know about floating-point - numbers. -* String Conversion Precision:: The String Value Can Lie. -* Unexpected Results:: Floating Point Numbers Are Not - Abstract Numbers. -* POSIX Floating Point Problems:: Standards Versus Existing Practice. -* Integer Programming:: Effective integer programming. -* Floating-point Programming:: Effective Floating-point Programming. -* Floating-point Representation:: Binary floating-point representation. -* Floating-point Context:: Floating-point context. -* Rounding Mode:: Floating-point rounding mode. -* Gawk and MPFR:: How `gawk' provides - arbitrary-precision arithmetic. -* Arbitrary Precision Floats:: Arbitrary Precision Floating-point - Arithmetic with `gawk'. -* Setting Precision:: Setting the working precision. -* Setting Rounding Mode:: Setting the rounding mode. -* Floating-point Constants:: Representing floating-point constants. -* Changing Precision:: Changing the precision of a number. -* Exact Arithmetic:: Exact arithmetic with floating-point - numbers. +* Debugging Summary:: Debugging summary. +* Computer Arithmetic:: A quick intro to computer math. +* Math Definitions:: Defining terms used. +* MPFR features:: The MPFR features in `gawk'. +* FP Math Caution:: Things to know. +* Inexactness of computations:: Floating point math is not exact. +* Inexact representation:: Numbers are not exactly represented. +* Comparing FP Values:: How to compare floating point values. +* Errors accumulate:: Errors get bigger as they go. +* Getting Accuracy:: Getting more accuracy takes some work. +* Try To Round:: Add digits and round. +* Setting precision:: How to set the precision. +* Setting the rounding mode:: How to set the rounding mode. * Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic with `gawk'. +* POSIX Floating Point Problems:: Standards Versus Existing Practice. +* Floating point summary:: Summary of floating point discussion. * Extension Intro:: What is an extension. * Plugin License:: A note about licensing. * Extension Mechanism Outline:: An outline of how it works. @@ -574,6 +583,8 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Extension Sample Time:: An interface to `gettimeofday()' and `sleep()'. * gawkextlib:: The `gawkextlib' project. +* Extension summary:: Extension summary. +* Extension Exercises:: Exercises. * V7/SVR3.1:: The major changes between V7 and System V Release 3.1. * SVR4:: Minor changes between System V @@ -590,6 +601,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) ranges. * Contributors:: The major contributors to `gawk'. +* History summary:: History summary. * Gawk Distribution:: What is in the `gawk' distribution. * Getting:: How to get the distribution. @@ -628,6 +640,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Bugs:: Reporting Problems and Bugs. * Other Versions:: Other freely available `awk' implementations. +* Installation summary:: Summary of installation. * Compatibility Mode:: How to disable certain `gawk' extensions. * Additions:: Making Additions To `gawk'. @@ -636,8 +649,8 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) `gawk'. * New Ports:: Porting `gawk' to a new operating system. -* Derived Files:: Why derived files are kept in the - `git' repository. +* Derived Files:: Why derived files are kept in the Git + repository. * Future Extensions:: New features that may be implemented one day. * Implementation Limitations:: Some limitations of the @@ -648,18 +661,19 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) * Extension Other Design Decisions:: Some other design decisions. * Extension Future Growth:: Some room for future growth. * Old Extension Mechanism:: Some compatibility for old extensions. +* Notes summary:: Summary of implementation notes. * Basic High Level:: The high level view. * Basic Data Typing:: A very quick intro to data types. - To Miriam, for making me complete. + To my parents, for their love, and for the wonderful example they +set for me. - To Chana, for the joy you bring us. + To my wife Miriam, for making me complete. Thank you for building +your life together with me. - To Rivka, for the exponential increase. + To our children Chana, Rivka, Nachum and Malka, for enrichening our +lives in innumerable ways. - To Nachum, for the added dimension. - - To Malka, for the new beginning. File: gawk.info, Node: Foreword, Next: Preface, Prev: Top, Up: Top @@ -755,12 +769,10 @@ Preface Several kinds of tasks occur repeatedly when working with text files. You might want to extract certain lines and discard the rest. Or you -may need to make changes wherever certain patterns appear, but leave -the rest of the file alone. Writing single-use programs for these -tasks in languages such as C, C++, or Java is time-consuming and -inconvenient. Such jobs are often easier with `awk'. The `awk' -utility interprets a special-purpose programming language that makes it -easy to handle simple data-reformatting jobs. +may need to make changes wherever certain patterns appear, but leave the +rest of the file alone. Such jobs are often easy with `awk'. The +`awk' utility interprets a special-purpose programming language that +makes it easy to handle simple data-reformatting jobs. The GNU implementation of `awk' is called `gawk'; if you invoke it with the proper options or environment variables (*note Options::), it @@ -791,6 +803,10 @@ and other `awk' implementations. * Perform simple network communications + * Profile and debug `awk' programs. + + * Extend the language with functions written in C or C++. + This Info file teaches you about the `awk' language and how you can use it effectively. You should already be familiar with basic system commands, such as `cat' and `ls',(2) as well as basic shell facilities, @@ -799,13 +815,12 @@ such as input/output (I/O) redirection and pipes. Implementations of the `awk' language are available for many different computing environments. This Info file, while describing the `awk' language in general, also describes the particular implementation -of `awk' called `gawk' (which stands for "GNU awk"). `gawk' runs on a -broad range of Unix systems, ranging from Intel(R)-architecture -PC-based computers up through large-scale systems, such as Crays. -`gawk' has also been ported to Mac OS X, Microsoft Windows (all -versions) and OS/2 PCs, and VMS. (Some other, obsolete systems to -which `gawk' was once ported are no longer supported and the code for -those systems has been removed.) +of `awk' called `gawk' (which stands for "GNU `awk'"). `gawk' runs on +a broad range of Unix systems, ranging from Intel-architecture PC-based +computers up through large-scale systems. `gawk' has also been ported +to Mac OS X, Microsoft Windows (all versions) and OS/2 PCs, and OpenVMS. +(Some other, obsolete systems to which `gawk' was once ported are no +longer supported and the code for those systems has been removed.) * Menu: @@ -822,7 +837,7 @@ those systems has been removed.) ---------- Footnotes ---------- - (1) The 2008 POSIX standard is online at + (1) The 2008 POSIX standard is accessible online at `http://www.opengroup.org/onlinepubs/9699919799/'. (2) These commands are available on POSIX-compliant systems, as well @@ -866,7 +881,7 @@ contributed parts of the code as well. In 1988 and 1989, David Trueman, with help from me, thoroughly reworked `gawk' for compatibility with the newer `awk'. Circa 1994, I became the primary maintainer. Current development focuses on bug fixes, performance improvements, -standards compliance, and occasionally, new features. +standards compliance and, occasionally, new features. In May of 1997, Ju"rgen Kahrs felt the need for network access from `awk', and with a little help from me, set about adding features to do @@ -890,22 +905,19 @@ A Rose by Any Other Name The `awk' language has evolved over the years. Full details are provided in *note Language History::. The language described in this -Info file is often referred to as "new `awk'" (`nawk'). - - Because of this, there are systems with multiple versions of `awk'. -Some systems have an `awk' utility that implements the original version -of the `awk' language and a `nawk' utility for the new version. Others -have an `oawk' version for the "old `awk'" language and plain `awk' for -the new one. Still others only have one version, which is usually the -new one.(1) - - All in all, this makes it difficult for you to know which version of -`awk' you should run when writing your programs. The best advice we -can give here is to check your local documentation. Look for `awk', -`oawk', and `nawk', as well as for `gawk'. It is likely that you -already have some version of new `awk' on your system, which is what -you should use when running your programs. (Of course, if you're -reading this Info file, chances are good that you have `gawk'!) +Info file is often referred to as "new `awk'". By analogy, the +original version of `awk' is referred to as "old `awk'." + + Today, on most systems, when you run the `awk' utility, you get some +version of new `awk'.(1) If your system's standard `awk' is the old +one, you will see something like this if you try the test program: + + $ awk 1 /dev/null + error--> awk: syntax error near line 1 + error--> awk: bailing out near line 1 + +In this case, you should find a version of new `awk', or just install +`gawk'! Throughout this Info file, whenever we refer to a language feature that should be available in any complete implementation of POSIX `awk', @@ -914,7 +926,9 @@ specific to the GNU implementation, we use the term `gawk'. ---------- Footnotes ---------- - (1) Often, these systems use `gawk' for their `awk' implementation! + (1) Only Solaris systems still use an old `awk' for the default +`awk' utility. A more modern `awk' lives in `/usr/xpg6/bin' on these +systems. File: gawk.info, Node: This Manual, Next: Conventions, Prev: Names, Up: Preface @@ -1043,7 +1057,7 @@ material for those who are completely unfamiliar with computer programming. The *note Glossary::, defines most, if not all, the significant -terms used throughout the book. If you find terms that you aren't +terms used throughout the Info file. If you find terms that you aren't familiar with, try looking them up here. *note Copying::, and *note GNU Free Documentation License::, present @@ -1067,7 +1081,7 @@ formatting language. A single Texinfo source file is used to produce both the printed and online versions of the documentation. This minor node briefly documents the typographical conventions used in Texinfo. - Examples you would type at the command-line are preceded by the + Examples you would type at the command line are preceded by the common shell primary and secondary prompts, `$' and `>'. Input that you type is shown `like this'. Output from the command is preceded by the glyph "-|". This typically represents the command's standard @@ -1086,6 +1100,10 @@ key and another key, at the same time. For example, a `Ctrl-d' is typed by first pressing and holding the `CONTROL' key, next pressing the `d' key and finally releasing both keys. + For the sake of brevity, throughout this Info file, we refer to +Brian Kernighan's version of `awk' as "BWK `awk'." (*Note Other +Versions::, for information on his and other versions.) + Dark Corners ------------ @@ -1121,7 +1139,7 @@ editor. GNU Emacs is the most widely used version of Emacs today. Software Foundation to create a complete, freely distributable, POSIX-compliant computing environment. The FSF uses the "GNU General Public License" (GPL) to ensure that their software's source code is -always available to the end user. A copy of the GPL is included for +always available to the end user. A copy of the GPL is included for your reference (*note Copying::). The GPL applies to the C language source code for `gawk'. To find out more about the FSF and the GNU Project online, see the GNU Project's home page (http://www.gnu.org). @@ -1136,17 +1154,10 @@ released but remains in an early stage of development. Until the GNU operating system is more fully developed, you should consider using GNU/Linux, a freely distributable, Unix-like operating -system for Intel(R), Power Architecture, Sun SPARC, IBM S/390, and other +system for Intel, Power Architecture, Sun SPARC, IBM S/390, and other systems.(2) Many GNU/Linux distributions are available for download from the Internet. - (There are numerous other freely available, Unix-like operating -systems based on the Berkeley Software Distribution, and some of them -use recent versions of `gawk' for their versions of `awk'. NetBSD -(http://www.netbsd.org), FreeBSD (http://www.freebsd.org), and OpenBSD -(http://www.openbsd.org) are three of the most popular ones, but there -are others.) - The Info file itself has gone through a number of previous editions. Paul Rubin wrote the very first draft of `The GAWK Manual'; it was around 40 pages in size. Diane Close and Richard Stallman improved it, @@ -1160,19 +1171,18 @@ published the first two editions under the title `The GNU Awk User's Guide'. This edition maintains the basic structure of the previous editions. -For Edition 4.0, the content has been thoroughly reviewed and updated. -All references to `gawk' versions prior to 4.0 have been removed. Of -significant note for this edition was *note Debugger::. +For FSF edition 4.0, the content has been thoroughly reviewed and +updated. All references to `gawk' versions prior to 4.0 have been +removed. Of significant note for this edition was *note Debugger::. - For edition 4.1, the content has been reorganized into parts, and -the major new additions are *note Arbitrary Precision Arithmetic::, and -*note Dynamic Extensions::. + For FSF edition 4.1, the content has been reorganized into parts, +and the major new additions are *note Arbitrary Precision Arithmetic::, +and *note Dynamic Extensions::. - `GAWK: Effective AWK Programming' will undoubtedly continue to -evolve. An electronic version comes with the `gawk' distribution from -the FSF. If you find an error in this Info file, please report it! -*Note Bugs::, for information on submitting problem reports -electronically. + This Info file will undoubtedly continue to evolve. An electronic +version comes with the `gawk' distribution from the FSF. If you find +an error in this Info file, please report it! *Note Bugs::, for +information on submitting problem reports electronically. ---------- Footnotes ---------- @@ -1199,14 +1209,17 @@ something more broad, I acquired the `awk.info' domain. contributed code: the archive did not grow and the domain went unused for several years. - Fortunately, late in 2008, a volunteer took on the task of setting up -an `awk'-related web site--`http://awk.info'--and did a very nice job. + Late in 2008, a volunteer took on the task of setting up an +`awk'-related web site--`http://awk.info'--and did a very nice job. If you have written an interesting `awk' program, or have written a `gawk' extension that you would like to share with the rest of the world, please see `http://awk.info/?contribute' for how to contribute it to the web site. + As of this writing, this website is in search of a maintainer; please +contact me if you are interested. + File: gawk.info, Node: Acknowledgments, Prev: How To Contribute, Up: Preface @@ -1279,12 +1292,26 @@ be a pleasure working with this team of fine people. Notable code and documentation contributions were made by a number of people. *Note Contributors::, for the full list. + Thanks to Patrice Dumas for the new `makeinfo' program. Thanks to +Karl Berry who continues to work to keep the Texinfo markup language +sane. + + Robert P.J. Day, Michael Brennan and Brian Kernighan kindly acted as +reviewers for the 2015 edition of this Info file. Their feedback helped +improve the final work. + I would like to thank Brian Kernighan for invaluable assistance during the testing and debugging of `gawk', and for ongoing help and advice in clarifying numerous points about the language. We could not have done nearly as good a job on either `gawk' or its documentation without his help. + Brian is in a class by himself as a programmer and technical author. +I have to thank him (yet again) for his ongoing friendship and the role +model he has been for me for close to 30 years! Having him as a +reviewer is an exciting privilege. It has also been extremely +humbling... + I must thank my wonderful wife, Miriam, for her patience through the many versions of this project, for her proofreading, and for sharing me with the computer. I would like to thank my parents for their love, @@ -1293,12 +1320,6 @@ also must acknowledge my gratitude to G-d, for the many opportunities He has sent my way, as well as for the gifts He has given me with which to take advantage of those opportunities. - -Arnold Robbins -Nof Ayalon -ISRAEL -May, 2013 - File: gawk.info, Node: Getting Started, Next: Invoking Gawk, Prev: Preface, Up: Top @@ -1327,7 +1348,7 @@ for now. *Note User-defined::.) Each rule specifies one pattern to search for and one action to perform upon finding the pattern. Syntactically, a rule consists of a pattern followed by an action. -The action is enclosed in curly braces to separate it from the pattern. +The action is enclosed in braces to separate it from the pattern. Newlines usually separate rules. Therefore, an `awk' program looks like this: @@ -1350,6 +1371,7 @@ like this: * Other Features:: Other Features of `awk'. * When:: When to use `gawk' and when to use other things. +* Intro Summary:: Summary of the introduction. File: gawk.info, Node: Running gawk, Next: Sample Data Files, Up: Getting Started @@ -1375,7 +1397,7 @@ variations of each. * One-shot:: Running a short throwaway `awk' program. -* Read Terminal:: Using no input files (input from terminal +* Read Terminal:: Using no input files (input from the keyboard instead). * Long:: Putting permanent `awk' programs in files. @@ -1425,7 +1447,7 @@ following command line: awk 'PROGRAM' `awk' applies the PROGRAM to the "standard input", which usually means -whatever you type on the terminal. This continues until you indicate +whatever you type on the keyboard. This continues until you indicate end-of-file by typing `Ctrl-d'. (On other operating systems, the end-of-file character may be different. For example, on OS/2, it is `Ctrl-z'.) @@ -1433,15 +1455,23 @@ end-of-file character may be different. For example, on OS/2, it is As an example, the following program prints a friendly piece of advice (from Douglas Adams's `The Hitchhiker's Guide to the Galaxy'), to keep you from worrying about the complexities of computer -programming(1) (`BEGIN' is a feature we haven't discussed yet): +programming: - $ awk "BEGIN { print \"Don't Panic!\" }" + $ awk "BEGIN { print "Don\47t Panic!" }" -| Don't Panic! - This program does not read any input. The `\' before each of the -inner double quotes is necessary because of the shell's quoting -rules--in particular because it mixes both single quotes and double -quotes.(2) + `awk' executes statements associated with `BEGIN' before reading any +input. If there are no other statements in your program, as is the +case here, `awk' just stops, instead of trying to read input it doesn't +know how to process. The `\47' is a magic way of getting a single +quote into the program, without having to engage in ugly shell quoting +tricks. + + NOTE: As a side note, if you use Bash as your shell, you should + execute the command `set +H' before running this program + interactively, to disable the C shell-style command history, which + treats `!' as a special character. We recommend putting this + command into your personal startup file. This next simple `awk' program emulates the `cat' utility; it copies whatever you type on the keyboard to its standard output (why this @@ -1458,17 +1488,6 @@ works is explained shortly). -| What, me worry? Ctrl-d - ---------- Footnotes ---------- - - (1) If you use Bash as your shell, you should execute the command -`set +H' before running this program interactively, to disable the C -shell-style command history, which treats `!' as a special character. -We recommend putting this command into your personal startup file. - - (2) Although we generally recommend the use of single quotes around -the program text, double quotes are needed here in order to put the -single quote into the message. - File: gawk.info, Node: Long, Next: Executable Scripts, Prev: Read Terminal, Up: Running gawk @@ -1482,8 +1501,8 @@ tell `awk' to use that file for its program, you type: awk -f SOURCE-FILE INPUT-FILE1 INPUT-FILE2 ... The `-f' instructs the `awk' utility to get the `awk' program from -the file SOURCE-FILE. Any file name can be used for SOURCE-FILE. For -example, you could put the program: +the file SOURCE-FILE (*note Options::). Any file name can be used for +SOURCE-FILE. For example, you could put the program: BEGIN { print "Don't Panic!" } @@ -1523,8 +1542,8 @@ like this: BEGIN { print "Don't Panic!" } After making this file executable (with the `chmod' utility), simply -type `advice' at the shell and the system arranges to run `awk'(2) as -if you had typed `awk -f advice': +type `advice' at the shell and the system arranges to run `awk' as if +you had typed `awk -f advice': $ chmod +x advice $ advice @@ -1538,7 +1557,24 @@ at the shell.) program that users can invoke without their having to know that the program is written in `awk'. - Portability Issues with `#!' + Understanding `#!' + + `awk' is an "interpreted" language. This means that the `awk' +utility reads your program and then processes your data according to +the instructions in your program. (This is different from a "compiled" +language such as C, where your program is first compiled into machine +code that is executed directly by your system's hardware.) The `awk' +utility is thus termed an "interpreter". Many modern languages are +interperted. + + The line beginning with `#!' lists the full file name of an +interpreter to run and a single optional initial command-line argument +to pass to that interpreter. The operating system then runs the +interpreter with the given argument and the full argument list of the +executed program. The first argument in the list is the full file name +of the `awk' program. The rest of the argument list contains either +options to `awk', or data files, or both. Note that on many systems +`awk' may be found in `/usr/bin' instead of in `/bin'. Caveat Emptor. Some systems limit the length of the interpreter name to 32 characters. Often, this can be dealt with by using a symbolic link. @@ -1560,15 +1596,6 @@ the name of your script (`advice'). (d.c.) Don't rely on the value of (1) The `#!' mechanism works on GNU/Linux systems, BSD-based systems and commercial Unix systems. - (2) The line beginning with `#!' lists the full file name of an -interpreter to run and an optional initial command-line argument to -pass to that interpreter. The operating system then runs the -interpreter with the given argument and the full argument list of the -executed program. The first argument in the list is the full file name -of the `awk' program. The rest of the argument list contains either -options to `awk', or data files, or both. Note that on many systems -`awk' may be found in `/usr/bin' instead of in `/bin'. Caveat Emptor. - File: gawk.info, Node: Comments, Next: Quoting, Prev: Executable Scripts, Up: Running gawk @@ -1606,7 +1633,7 @@ at a later time. will probably print strange messages about syntax errors. For example, look at the following: - $ awk '{ print "hello" } # let's be cute' + $ awk 'BEGIN { print "hello" } # let's be cute' > The shell sees that the first two quotes match, and that a new @@ -1646,6 +1673,23 @@ knowledge of shell quoting rules. The following rules apply only to POSIX-compliant, Bourne-style shells (such as Bash, the GNU Bourne-Again Shell). If you use the C shell, you're on your own. + Before diving into the rules, we introduce a concept that appears +throughout this Info file, which is that of the "null", or empty, +string. + + The null string is character data that has no value. In other +words, it is empty. It is written in `awk' programs like this: `""'. +In the shell, it can be written using single or double quotes: `""' or +`'''. While the null string has no characters in it, it does exist. +Consider this command: + + $ echo "" + +Here, the `echo' utility receives a single argument, even though that +argument has no characters in it. In the rest of this Info file, we use +the terms "null string" and "empty string" interchangeably. Now, on to +the quoting rules. + * Quoted items can be concatenated with nonquoted items as well as with other quoted items. The shell turns everything into one argument for the command. @@ -1679,9 +1723,9 @@ Shell). If you use the C shell, you're on your own. Note that the single quote is not special within double quotes. * Null strings are removed when they occur as part of a non-null - command-line argument, while explicit non-null objects are kept. - For example, to specify that the field separator `FS' should be - set to the null string, use: + command-line argument, while explicit null objects are kept. For + example, to specify that the field separator `FS' should be set to + the null string, use: awk -F "" 'PROGRAM' FILES # correct @@ -1774,10 +1818,10 @@ one "record". In the data file `mail-list', each record contains the name of a person, his/her phone number, his/her email-address, and a code for -their relationship with the author of the list. An `A' in the last -column means that the person is an acquaintance. An `F' in the last -column means that the person is a friend. An `R' means that the person -is a relative: +their relationship with the author of the list. The columns are +aligned using spaces. An `A' in the last column means that the person +is an acquaintance. An `F' in the last column means that the person is +a friend. An `R' means that the person is a relative: Amelia 555-5553 amelia.zodiacusque@gmail.com F Anthony 555-3412 anthony.asserturo@hotmail.com A @@ -1796,7 +1840,8 @@ shipments during the year. Each record contains the month, the number of green crates shipped, the number of red boxes shipped, the number of orange bags shipped, and the number of blue packages shipped, respectively. There are 16 entries, covering the 12 months of last year -and the first four months of the current year. +and the first four months of the current year. An empty line separates +the data for the two years. Jan 13 25 15 115 Feb 15 32 24 226 @@ -1859,10 +1904,10 @@ for _every_ input line. If the action is omitted, the default action is to print all lines that match the pattern. Thus, we could leave out the action (the `print' statement and the -curly braces) in the previous example and the result would be the same: -`awk' prints all lines matching the pattern `li'. By comparison, -omitting the `print' statement but retaining the curly braces makes an -empty action that does nothing (i.e., no lines are printed). +braces) in the previous example and the result would be the same: `awk' +prints all lines matching the pattern `li'. By comparison, omitting +the `print' statement but retaining the braces makes an empty action +that does nothing (i.e., no lines are printed). Many practical `awk' programs are just a line or two. Following is a collection of useful, short programs to get you started. Some of these @@ -1876,26 +1921,30 @@ often more than one way to do things in `awk'. At some point, you may want to look back at these examples and see if you can come up with different ways to do the same things shown here: - * Print the length of the longest input line: - - awk '{ if (length($0) > max) max = length($0) } - END { print max }' data - * Print every line that is longer than 80 characters: awk 'length($0) > 80' data The sole rule has a relational expression as its pattern and it - has no action--so the default action, printing the record, is used. + has no action--so it uses the default action, printing the record. + + * Print the length of the longest input line: + + awk '{ if (length($0) > max) max = length($0) } + END { print max }' data + + The code associated with `END' executes after all input has been + read; it's the other side of the coin to `BEGIN'. * Print the length of the longest line in `data': - expand data | awk '{ if (x < length()) x = length() } + expand data | awk '{ if (x < length($0)) x = length($0) } END { print "maximum line length is " x }' - The input is processed by the `expand' utility to change TABs into - spaces, so the widths compared are actually the right-margin - columns. + This example differs slightly from the previous one: The input is + processed by the `expand' utility to change TABs into spaces, so + the widths compared are actually the right-margin columns, as + opposed to the number of input characters on each line. * Print every line that has at least one field: @@ -1943,9 +1992,8 @@ File: gawk.info, Node: Two Rules, Next: More Complex, Prev: Very Simple, Up: The `awk' utility reads the input files one line at a time. For each line, `awk' tries the patterns of each of the rules. If several -patterns match, then several actions are run in the order in which they -appear in the `awk' program. If no patterns match, then no actions are -run. +patterns match, then several actions execute in the order in which they +appear in the `awk' program. If no patterns match, then no actions run. After processing all the rules that match the line (and perhaps there are none), `awk' reads the next line. (However, *note Next @@ -1993,8 +2041,8 @@ summarize, select, and rearrange the output of another utility. It uses features that haven't been covered yet, so don't worry if you don't understand all the details: - LC_ALL=C ls -l | awk '$6 == "Nov" { sum += $5 } - END { print sum }' + ls -l | awk '$6 == "Nov" { sum += $5 } + END { print sum }' This command prints the total number of bytes in all the files in the current directory that were last modified in November (of any year). @@ -2021,12 +2069,12 @@ contains the file name.(1) The `$6 == "Nov"' in our `awk' program is an expression that tests whether the sixth field of the output from `ls -l' matches the string -`Nov'. Each time a line has the string `Nov' for its sixth field, the -action `sum += $5' is performed. This adds the fifth field (the file's -size) to the variable `sum'. As a result, when `awk' has finished -reading all the input lines, `sum' is the total of the sizes of the -files whose lines matched the pattern. (This works because `awk' -variables are automatically initialized to zero.) +`Nov'. Each time a line has the string `Nov' for its sixth field, +`awk' performs the action `sum += $5'. This adds the fifth field (the +file's size) to the variable `sum'. As a result, when `awk' has +finished reading all the input lines, `sum' is the total of the sizes +of the files whose lines matched the pattern. (This works because +`awk' variables are automatically initialized to zero.) After the last line of output from `ls' has been processed, the `END' rule executes and prints the value of `sum'. In this example, @@ -2078,15 +2126,15 @@ We have generally not used backslash continuation in our sample programs. `gawk' places no limit on the length of a line, so backslash continuation is never strictly necessary; it just makes programs more readable. For this same reason, as well as for clarity, we have kept -most statements short in the sample programs presented throughout the -Info file. Backslash continuation is most useful when your `awk' -program is in a separate source file instead of entered from the -command line. You should also note that many `awk' implementations are -more particular about where you may use backslash continuation. For -example, they may not allow you to split a string constant using -backslash continuation. Thus, for maximum portability of your `awk' -programs, it is best not to split your lines in the middle of a regular -expression or a string. +most statements short in the programs presented throughout the Info +file. Backslash continuation is most useful when your `awk' program is +in a separate source file instead of entered from the command line. +You should also note that many `awk' implementations are more +particular about where you may use backslash continuation. For example, +they may not allow you to split a string constant using backslash +continuation. Thus, for maximum portability of your `awk' programs, it +is best not to split your lines in the middle of a regular expression +or a string. CAUTION: _Backslash continuation does not work as described with the C shell._ It works for `awk' programs in files and for @@ -2128,7 +2176,7 @@ comment, it ignores _everything_ on the rest of the line. For example: > BEGIN rule > }' error--> gawk: cmd. line:2: BEGIN rule - error--> gawk: cmd. line:2: ^ parse error + error--> gawk: cmd. line:2: ^ syntax error In this case, it looks like the backslash would continue the comment onto the next line. However, the backslash-newline combination is never @@ -2174,10 +2222,10 @@ determining the type of a variable, and array sorting. As we develop our presentation of the `awk' language, we introduce most of the variables and many of the functions. They are described -systematically in *note Built-in Variables::, and *note Built-in::. +systematically in *note Built-in Variables::, and in *note Built-in::. -File: gawk.info, Node: When, Prev: Other Features, Up: Getting Started +File: gawk.info, Node: When, Next: Intro Summary, Prev: Other Features, Up: Getting Started 1.8 When to Use `awk' ===================== @@ -2201,20 +2249,45 @@ edit-compile-test-debug cycle of software development. retargetable assembler for eight-bit microprocessors (*note Glossary::, for more information), and a microcode assembler for a special-purpose Prolog computer. While the original `awk''s capabilities were strained -by tasks of such complexity, modern versions are more capable. Even -Brian Kernighan's version of `awk' has fewer predefined limits, and -those that it has are much larger than they used to be. +by tasks of such complexity, modern versions are more capable. If you find yourself writing `awk' scripts of more than, say, a few hundred lines, you might consider using a different programming -language. Emacs Lisp is a good choice if you need sophisticated string -or pattern matching capabilities. The shell is also good at string and -pattern matching; in addition, it allows powerful use of the system -utilities. More conventional languages, such as C, C++, and Java, offer -better facilities for system programming and for managing the complexity -of large programs. Programs in these languages may require more lines -of source code than the equivalent `awk' programs, but they are easier -to maintain and usually run more efficiently. +language. The shell is good at string and pattern matching; in +addition, it allows powerful use of the system utilities. Python +offers a nice balance between high-level ease of programming and access +to system facilities.(1) + + ---------- Footnotes ---------- + + (1) Other popular scripting languages include Ruby and Perl. + + +File: gawk.info, Node: Intro Summary, Prev: When, Up: Getting Started + +1.9 Summary +=========== + + * Programs in `awk' consist of PATTERN-ACTION pairs. + + * An ACTION without a PATTERN always runs. The default ACTION for a + pattern without one is `{ print $0 }'. + + * Use either `awk 'PROGRAM' FILES' or `awk -f PROGRAM-FILE FILES' to + run `awk'. + + * You may use the special `#!' header line to create `awk' programs + that are directly executable. + + * Comments in `awk' programs start with `#' and continue to the end + of the same line. + + * Be aware of quoting issues when writing `awk' programs as part of + a larger shell script (or MS-Windows batch file). + + * You may use backslash continuation to continue a source line. + Lines are automatically continued after a comma, open brace, + question mark, colon, `||', `&&', `do' and `else'. File: gawk.info, Node: Invoking Gawk, Next: Regexp, Prev: Getting Started, Up: Top @@ -2246,6 +2319,7 @@ this major node that don't interest you right now. * Loading Shared Libraries:: Loading shared libraries into your program. * Obsolete:: Obsolete Options and/or features. * Undocumented:: Undocumented Options and Features. +* Invoking Summary:: Invocation summary. File: gawk.info, Node: Command Line, Next: Options, Up: Invoking Gawk @@ -2257,8 +2331,8 @@ There are two ways to run `awk'--with an explicit program or with one or more program files. Here are templates for both of them; items enclosed in [...] in these templates are optional: - awk [OPTIONS] -f progfile [`--'] FILE ... - awk [OPTIONS] [`--'] 'PROGRAM' FILE ... + `awk' [OPTIONS] `-f' PROGFILE [`--'] FILE ... + `awk' [OPTIONS] [`--'] `'PROGRAM'' FILE ... Besides traditional one-letter POSIX-style options, `gawk' also supports GNU long options. @@ -2344,26 +2418,26 @@ The following list describes options mandated by the POSIX standard: treated as single-byte characters. Normally, `gawk' follows the POSIX standard and attempts to process - its input data according to the current locale. This can often - involve converting multibyte characters into wide characters - (internally), and can lead to problems or confusion if the input - data does not contain valid multibyte characters. This option is - an easy way to tell `gawk': "hands off my data!". + its input data according to the current locale (*note Locales::). + This can often involve converting multibyte characters into wide + characters (internally), and can lead to problems or confusion if + the input data does not contain valid multibyte characters. This + option is an easy way to tell `gawk': "hands off my data!". `-c' `--traditional' Specify "compatibility mode", in which the GNU extensions to the - `awk' language are disabled, so that `gawk' behaves just like - Brian Kernighan's version `awk'. *Note POSIX/GNU::, which - summarizes the extensions. Also see *note Compatibility Mode::. + `awk' language are disabled, so that `gawk' behaves just like BWK + `awk'. *Note POSIX/GNU::, which summarizes the extensions. Also + see *note Compatibility Mode::. `-C' `--copyright' Print the short version of the General Public License and then exit. -`-d[FILE]' -`--dump-variables[=FILE]' +`-d'[FILE] +`--dump-variables'[`='FILE] Print a sorted list of global variables, their types, and final values to FILE. If no FILE is provided, print this list to the file named `awkvars.out' in the current directory. No space is @@ -2377,25 +2451,25 @@ The following list describes options mandated by the POSIX standard: particularly easy mistake to make with simple variable names like `i', `j', etc.) -`-D[FILE]' -`--debug=[FILE]' +`-D'[FILE] +`--debug'[`='FILE] Enable debugging of `awk' programs (*note Debugging::). By default, the debugger reads commands interactively from the - terminal. The optional FILE argument allows you to specify a file + keyboard. The optional FILE argument allows you to specify a file with a list of commands for the debugger to execute non-interactively. No space is allowed between the `-D' and FILE, if FILE is supplied. -`-e PROGRAM-TEXT' -`--source PROGRAM-TEXT' +`-e' PROGRAM-TEXT +`--source' PROGRAM-TEXT Provide program source code in the PROGRAM-TEXT. This option allows you to mix source code in files with source code that you enter on the command line. This is particularly useful when you have library functions that you want to use from your command-line programs (*note AWKPATH Variable::). -`-E FILE' -`--exec FILE' +`-E' FILE +`--exec' FILE Similar to `-f', read `awk' program text from FILE. There are two differences from `-f': @@ -2408,9 +2482,9 @@ The following list describes options mandated by the POSIX standard: This option is particularly necessary for World Wide Web CGI applications that pass arguments through the URL; using this option prevents a malicious (or other) user from passing in - options, assignments, or `awk' source code (via `--source') to the - CGI application. This option should be used with `#!' scripts - (*note Executable Scripts::), like so: + options, assignments, or `awk' source code (via `-e') to the CGI + application. This option should be used with `#!' scripts (*note + Executable Scripts::), like so: #! /usr/local/bin/gawk -E @@ -2428,37 +2502,41 @@ The following list describes options mandated by the POSIX standard: Print a "usage" message summarizing the short and long style options that `gawk' accepts and then exit. -`-i SOURCE-FILE' -`--include SOURCE-FILE' +`-i' SOURCE-FILE +`--include' SOURCE-FILE Read `awk' source library from SOURCE-FILE. This option is completely equivalent to using the `@include' directive inside your program. This option is very similar to the `-f' option, but there are two important differences. First, when `-i' is used, - the program source will not be loaded if it has been previously - loaded, whereas the `-f' will always load the file. Second, - because this option is intended to be used with code libraries, - `gawk' does not recognize such files as constituting main program - input. Thus, after processing an `-i' argument, `gawk' still - expects to find the main source code via the `-f' option or on the - command-line. - -`-l LIB' -`--load LIB' - Load a shared library LIB. This searches for the library using the - `AWKLIBPATH' environment variable. The correct library suffix for - your platform will be supplied by default, so it need not be - specified in the library name. The library initialization routine - should be named `dl_load()'. An alternative is to use the `@load' - keyword inside the program to load a shared library. - -`-L [value]' -`--lint[=value]' + the program source is not loaded if it has been previously loaded, + whereas with `-f', `gawk' always loads the file. Second, because + this option is intended to be used with code libraries, `gawk' + does not recognize such files as constituting main program input. + Thus, after processing an `-i' argument, `gawk' still expects to + find the main source code via the `-f' option or on the command + line. + +`-l' EXT +`--load' EXT + Load a dynamic extension named EXT. Extensions are stored as + system shared libraries. This option searches for the library + using the `AWKLIBPATH' environment variable. The correct library + suffix for your platform will be supplied by default, so it need + not be specified in the extension name. The extension + initialization routine should be named `dl_load()'. An + alternative is to use the `@load' keyword inside the program to + load a shared library. This feature is described in detail in + *note Dynamic Extensions::. + +`-L'[VALUE] +`--lint'[`='VALUE] Warn about constructs that are dubious or nonportable to other - `awk' implementations. Some warnings are issued when `gawk' first - reads your program. Others are issued at runtime, as your program - executes. With an optional argument of `fatal', lint warnings - become fatal errors. This may be drastic, but its use will - certainly encourage the development of cleaner `awk' programs. + `awk' implementations. No space is allowed between the `-L' and + VALUE, if VALUE is supplied. Some warnings are issued when `gawk' + first reads your program. Others are issued at runtime, as your + program executes. With an optional argument of `fatal', lint + warnings become fatal errors. This may be drastic, but its use + will certainly encourage the development of cleaner `awk' programs. With an optional argument of `invalid', only warnings about things that are actually invalid are issued. (This is not fully implemented yet.) @@ -2474,7 +2552,7 @@ The following list describes options mandated by the POSIX standard: `--bignum' Force arbitrary precision arithmetic on numbers. This option has no effect if `gawk' is not compiled to use the GNU MPFR and MP - libraries (*note Gawk and MPFR::). + libraries (*note Arbitrary Precision Arithmetic::). `-n' `--non-decimal-data' @@ -2489,23 +2567,24 @@ The following list describes options mandated by the POSIX standard: Force the use of the locale's decimal point character when parsing numeric input data (*note Locales::). -`-o[FILE]' -`--pretty-print[=FILE]' +`-o'[FILE] +`--pretty-print'[`='FILE] Enable pretty-printing of `awk' programs. By default, output - program is created in a file named `awkprof.out'. The optional - FILE argument allows you to specify a different file name for the - output. No space is allowed between the `-o' and FILE, if FILE is - supplied. + program is created in a file named `awkprof.out' (*note + Profiling::). The optional FILE argument allows you to specify a + different file name for the output. No space is allowed between + the `-o' and FILE, if FILE is supplied. + + NOTE: In the past, this option would also execute your + program. This is no longer the case. `-O' `--optimize' Enable some optimizations on the internal representation of the - program. At the moment this includes just simple constant - folding. The `gawk' maintainer hopes to add more optimizations - over time. + program. At the moment this includes just simple constant folding. -`-p[FILE]' -`--profile[=FILE]' +`-p'[FILE] +`--profile'[`='FILE] Enable profiling of `awk' programs (*note Profiling::). By default, profiles are created in a file named `awkprof.out'. The optional FILE argument allows you to specify a different file name @@ -2530,7 +2609,7 @@ The following list describes options mandated by the POSIX standard: * Newlines are not allowed after `?' or `:' (*note Conditional Exp::). - * Specifying `-Ft' on the command-line does not set the value + * Specifying `-Ft' on the command line does not set the value of `FS' to be a single TAB character (*note Field Separators::). @@ -2538,15 +2617,15 @@ The following list describes options mandated by the POSIX standard: data (*note Locales::). If you supply both `--traditional' and `--posix' on the command - line, `--posix' takes precedence. `gawk' also issues a warning if - both options are supplied. + line, `--posix' takes precedence. `gawk' issues a warning if both + options are supplied. `-r' `--re-interval' Allow interval expressions (*note Regexp Operators::) in regexps. This is now `gawk''s default behavior. Nevertheless, this option remains both for backward compatibility, and for use in - combination with the `--traditional' option. + combination with `--traditional'. `-S' `--sandbox' @@ -2586,35 +2665,33 @@ having to be included into each individual program. (As mentioned in *note Definition Syntax::, function names must be unique.) With standard `awk', library functions can still be used, even if -the program is entered at the terminal, by specifying `-f /dev/tty'. +the program is entered at the keyboard, by specifying `-f /dev/tty'. After typing your program, type `Ctrl-d' (the end-of-file character) to terminate it. (You may also use `-f -' to read program source from the standard input but then you will not be able to also use the standard input as a source of data.) Because it is clumsy using the standard `awk' mechanisms to mix -source file and command-line `awk' programs, `gawk' provides the -`--source' option. This does not require you to pre-empt the standard -input for your source code; it allows you to easily mix command-line -and library source code (*note AWKPATH Variable::). The `--source' -option may also be used multiple times on the command line. +source file and command-line `awk' programs, `gawk' provides the `-e' +option. This does not require you to pre-empt the standard input for +your source code; it allows you to easily mix command-line and library +source code (*note AWKPATH Variable::). As with `-f', the `-e' and `-i' +options may also be used multiple times on the command line. - If no `-f' or `--source' option is specified, then `gawk' uses the -first non-option command-line argument as the text of the program -source code. + If no `-f' or `-e' option is specified, then `gawk' uses the first +non-option command-line argument as the text of the program source code. If the environment variable `POSIXLY_CORRECT' exists, then `gawk' -behaves in strict POSIX mode, exactly as if you had supplied the -`--posix' command-line option. Many GNU programs look for this -environment variable to suppress extensions that conflict with POSIX, -but `gawk' behaves differently: it suppresses all extensions, even -those that do not conflict with POSIX, and behaves in strict POSIX -mode. If `--lint' is supplied on the command line and `gawk' turns on -POSIX mode because of `POSIXLY_CORRECT', then it issues a warning -message indicating that POSIX mode is in effect. You would typically -set this variable in your shell's startup file. For a -Bourne-compatible shell (such as Bash), you would add these lines to -the `.profile' file in your home directory: +behaves in strict POSIX mode, exactly as if you had supplied `--posix'. +Many GNU programs look for this environment variable to suppress +extensions that conflict with POSIX, but `gawk' behaves differently: it +suppresses all extensions, even those that do not conflict with POSIX, +and behaves in strict POSIX mode. If `--lint' is supplied on the +command line and `gawk' turns on POSIX mode because of +`POSIXLY_CORRECT', then it issues a warning message indicating that +POSIX mode is in effect. You would typically set this variable in your +shell's startup file. For a Bourne-compatible shell (such as Bash), +you would add these lines to the `.profile' file in your home directory: POSIXLY_CORRECT=true export POSIXLY_CORRECT @@ -2651,6 +2728,10 @@ arguments, including variable assignments, are included. As each element of `ARGV' is processed, `gawk' sets the variable `ARGIND' to the index in `ARGV' of the current element. + Changing `ARGC' and `ARGV' in your `awk' program lets you control +how `awk' processes the input files; this is described in more detail +in *note ARGC and ARGV::. + The distinction between file name arguments and variable-assignment arguments is made when `awk' is about to open the next input file. At that point in execution, it checks the file name to see whether it is @@ -2666,18 +2747,18 @@ begins scanning the argument list. The variable values given on the command line are processed for escape sequences (*note Escape Sequences::). (d.c.) - In some earlier implementations of `awk', when a variable assignment -occurred before any file names, the assignment would happen _before_ -the `BEGIN' rule was executed. `awk''s behavior was thus inconsistent; -some command-line assignments were available inside the `BEGIN' rule, -while others were not. Unfortunately, some applications came to depend -upon this "feature." When `awk' was changed to be more consistent, the -`-v' option was added to accommodate applications that depended upon -the old behavior. + In some very early implementations of `awk', when a variable +assignment occurred before any file names, the assignment would happen +_before_ the `BEGIN' rule was executed. `awk''s behavior was thus +inconsistent; some command-line assignments were available inside the +`BEGIN' rule, while others were not. Unfortunately, some applications +came to depend upon this "feature." When `awk' was changed to be more +consistent, the `-v' option was added to accommodate applications that +depended upon the old behavior. The variable assignment feature is most useful for assigning to variables such as `RS', `OFS', and `ORS', which control input and -output formats before scanning the data files. It is also useful for +output formats, before scanning the data files. It is also useful for controlling state if multiple passes are needed over a data file. For example: @@ -2712,7 +2793,7 @@ with `getline' (*note Getline/File::). In addition, `gawk' allows you to specify the special file name `/dev/stdin', both on the command line and with `getline'. Some other versions of `awk' also support this, but it is not standard. (Some -operating systems provide a `/dev/stdin' file in the file system, +operating systems provide a `/dev/stdin' file in the filesystem; however, `gawk' always processes this file name itself.) @@ -2738,7 +2819,7 @@ File: gawk.info, Node: AWKPATH Variable, Next: AWKLIBPATH Variable, Up: Envir ---------------------------------------- The previous minor node described how `awk' program files can be named -on the command-line with the `-f' option. In most `awk' +on the command line with the `-f' option. In most `awk' implementations, you must supply a precise path name for each program file, unless the file is in the current directory. But in `gawk', if the file name supplied to the `-f' or `-i' options does not contain a @@ -2751,27 +2832,29 @@ colons(1). `gawk' gets its search path from the `AWKPATH' environment variable. If that variable does not exist, `gawk' uses a default path, `.:/usr/local/share/awk'.(2) - The search path feature is particularly useful for building libraries -of useful `awk' functions. The library files can be placed in a -standard directory in the default path and then specified on the + The search path feature is particularly helpful for building +libraries of useful `awk' functions. The library files can be placed +in a standard directory in the default path and then specified on the command line with a short file name. Otherwise, the full file name would have to be typed for each file. - By using the `-i' option, or the `--source' and `-f' options, your + By using the `-i' option, or the `-e' and `-f' options, your command-line `awk' programs can use facilities in `awk' library files (*note Library Functions::). Path searching is not done if `gawk' is in compatibility mode. This is true for both `--traditional' and `--posix'. *Note Options::. If the source code is not found after the initial search, the path -is searched again after adding the default `.awk' suffix to the -filename. +is searched again after adding the default `.awk' suffix to the file +name. NOTE: To include the current directory in the path, either place `.' explicitly in the path or write a null entry in the path. (A null entry is indicated by starting or ending the path with a - colon or by placing two colons next to each other (`::').) This - path search mechanism is similar to the shell's. + colon or by placing two colons next to each other [`::'].) This + path search mechanism is similar to the shell's. (See `The + Bourne-Again SHell manual'. + (http://www.gnu.org/software/bash/manual/)) However, `gawk' always looks in the current directory _before_ searching `AWKPATH', so there is no real reason to include the @@ -2779,8 +2862,8 @@ filename. If `AWKPATH' is not defined in the environment, `gawk' places its default search path into `ENVIRON["AWKPATH"]'. This makes it easy to -determine the actual search path that `gawk' will use from within an -`awk' program. +determine the actual search path that `gawk' used from within an `awk' +program. While you can change `ENVIRON["AWKPATH"]' within your `awk' program, this has no effect on the running program's behavior. This makes @@ -2804,13 +2887,13 @@ File: gawk.info, Node: AWKLIBPATH Variable, Next: Other Environment Variables, ------------------------------------------- The `AWKLIBPATH' environment variable is similar to the `AWKPATH' -variable, but it is used to search for shared libraries specified with -the `-l' option rather than for source files. If the library is not -found, the path is searched again after adding the appropriate shared -library suffix for the platform. For example, on GNU/Linux systems, -the suffix `.so' is used. The search path specified is also used for -libraries loaded via the `@load' keyword (*note Loading Shared -Libraries::). +variable, but it is used to search for loadable extensions (stored as +system shared libraries) specified with the `-l' option rather than for +source files. If the extension is not found, the path is searched +again after adding the appropriate shared library suffix for the +platform. For example, on GNU/Linux systems, the suffix `.so' is used. +The search path specified is also used for extensions loaded via the +`@load' keyword (*note Loading Shared Libraries::). File: gawk.info, Node: Other Environment Variables, Prev: AWKLIBPATH Variable, Up: Environment Variables @@ -2823,11 +2906,11 @@ they are more specialized. Those in the following list are meant to be used by regular users. `POSIXLY_CORRECT' - Causes `gawk' to switch POSIX compatibility mode, disabling all + Causes `gawk' to switch to POSIX compatibility mode, disabling all traditional and GNU extensions. *Note Options::. `GAWK_SOCK_RETRIES' - Controls the number of time `gawk' will attempt to retry a two-way + Controls the number of times `gawk' attempts to retry a two-way TCP/IP (socket) connection before giving up. *Note TCP/IP Networking::. @@ -2844,9 +2927,18 @@ used by regular users. the `gawk' developers for testing and tuning. They are subject to change. The variables are: +`AWKBUFSIZE' + This variable only affects `gawk' on POSIX-compliant systems. + With a value of `exact', `gawk' uses the size of each input file + as the size of the memory buffer to allocate for I/O. Otherwise, + the value should be a number, and `gawk' uses that number as the + size of the buffer to allocate. (When this variable is not set, + `gawk' uses the smaller of the file's size and the "default" + blocksize, which is usually the filesystems I/O blocksize.) + `AWK_HASH' - If this variable exists with a value of `gst', `gawk' will switch - to using the hash function from GNU Smalltalk for managing arrays. + If this variable exists with a value of `gst', `gawk' switches to + using the hash function from GNU Smalltalk for managing arrays. This function may be marginally faster than the standard function. `AWKREADFUNC' @@ -2949,7 +3041,7 @@ enclosed in double quotes. NOTE: Keep in mind that this is a language construct and the file name cannot be a string variable, but rather just a literal string - in double quotes. + constant in double quotes. The files to be included may be nested; e.g., given a third script, namely `test3': @@ -3004,22 +3096,22 @@ and this also applies to files named with `@include'. File: gawk.info, Node: Loading Shared Libraries, Next: Obsolete, Prev: Include Files, Up: Invoking Gawk -2.8 Loading Shared Libraries Into Your Program -============================================== +2.8 Loading Dynamic Extensions Into Your Program +================================================ This minor node describes a feature that is specific to `gawk'. - The `@load' keyword can be used to read external `awk' shared -libraries. This allows you to link in compiled code that may offer -superior performance and/or give you access to extended capabilities -not supported by the `awk' language. The `AWKLIBPATH' variable is used -to search for the shared library. Using `@load' is completely -equivalent to using the `-l' command-line option. + The `@load' keyword can be used to read external `awk' extensions +(stored as system shared libraries). This allows you to link in +compiled code that may offer superior performance and/or give you +access to extended capabilities not supported by the `awk' language. +The `AWKLIBPATH' variable is used to search for the extension. Using +`@load' is completely equivalent to using the `-l' command-line option. - If the shared library is not initially found in `AWKLIBPATH', another + If the extension is not initially found in `AWKLIBPATH', another search is conducted after appending the platform's default shared -library suffix to the filename. For example, on GNU/Linux systems, the -suffix `.so' is used. +library suffix to the file name. For example, on GNU/Linux systems, +the suffix `.so' is used. $ gawk '@load "ordchr"; BEGIN {print chr(65)}' -| A @@ -3031,7 +3123,7 @@ This is equivalent to the following example: For command-line usage, the `-l' option is more convenient, but `@load' is useful for embedding inside an `awk' source file that requires -access to a shared library. +access to an extension. *note Dynamic Extensions::, describes how to write extensions (in C or C++) that can be loaded with either `@load' or the `-l' option. @@ -3053,7 +3145,7 @@ worked. As of version 4.0, they are no longer interpreted specially by `gawk'. (Use `PROCINFO' instead; see *note Auto-set::.) -File: gawk.info, Node: Undocumented, Prev: Obsolete, Up: Invoking Gawk +File: gawk.info, Node: Undocumented, Next: Invoking Summary, Prev: Obsolete, Up: Invoking Gawk 2.10 Undocumented Options and Features ====================================== @@ -3063,6 +3155,48 @@ File: gawk.info, Node: Undocumented, Prev: Obsolete, Up: Invoking Gawk This minor node intentionally left blank. +File: gawk.info, Node: Invoking Summary, Prev: Undocumented, Up: Invoking Gawk + +2.11 Summary +============ + + * Use either `awk 'PROGRAM' FILES' or `awk -f PROGRAM-FILE FILES' to + run `awk'. + + * The three standard options for all versions of `awk' are `-f', + `-F' and `-v'. `gawk' supplies these and many others, as well as + corresponding GNU-style long options. + + * Non-option command-line arguments are usually treated as file + names, unless they have the form `VAR=VALUE', in which case they + are taken as variable assignments to be performed at that point in + processing the input. + + * All non-option command-line arguments, excluding the program text, + are placed in the `ARGV' array. Adjusting `ARGC' and `ARGV' + affects how `awk' processes input. + + * You can use a single minus sign (`-') to refer to standard input + on the command line. + + * `gawk' pays attention to a number of environment variables. + `AWKPATH', `AWKLIBPATH', and `POSIXLY_CORRECT' are the most + important ones. + + * `gawk''s exit status conveys information to the program that + invoked it. Use the `exit' statement from within an `awk' program + to set the exit status. + + * `gawk' allows you to include other `awk' source files into your + program using the `@include' statement and/or the `-i' and `-f' + command-line options. + + * `gawk' allows you to load additional functions written in C or C++ + using the `@load' statement and/or the `-l' option. (This + advanced feature is described later on in *note Dynamic + Extensions::.) + + File: gawk.info, Node: Regexp, Next: Reading Files, Prev: Invoking Gawk, Up: Top 3 Regular Expressions @@ -3077,7 +3211,7 @@ that matches every input record whose text belongs to that set. The simplest regular expression is a sequence of letters, numbers, or both. Such a regexp matches any string that contains that sequence. Thus, the regexp `foo' matches any string containing `foo'. Therefore, the -pattern `/foo/' matches any input record containing the three +pattern `/foo/' matches any input record containing the three adjacent characters `foo' _anywhere_ in the record. Other kinds of regexps let you specify more complicated classes of strings. @@ -3087,10 +3221,11 @@ you specify more complicated classes of strings. * Escape Sequences:: How to write nonprinting characters. * Regexp Operators:: Regular Expression Operators. * Bracket Expressions:: What can go between `[...]'. -* GNU Regexp Operators:: Operators specific to GNU software. -* Case-sensitivity:: How to do case-insensitive matching. * Leftmost Longest:: How much text matches. * Computed Regexps:: Using Dynamic Regexps. +* GNU Regexp Operators:: Operators specific to GNU software. +* Case-sensitivity:: How to do case-insensitive matching. +* Regexp Summary:: Regular expressions summary. File: gawk.info, Node: Regexp Usage, Next: Escape Sequences, Up: Regexp @@ -3102,8 +3237,8 @@ A regular expression can be used as a pattern by enclosing it in slashes. Then the regular expression is tested against the entire text of each record. (Normally, it only needs to match some part of the text in order to succeed.) For example, the following prints the -second field of each record that contains the string `li' anywhere in -it: +second field of each record where the string `li' appears anywhere in +the record: $ awk '/li/ { print $2 }' mail-list -| 555-5553 @@ -3188,8 +3323,8 @@ apply to both string constants and regexp constants: A literal backslash, `\'. `\a' - The "alert" character, `Ctrl-g', ASCII code 7 (BEL). (This - usually makes some sort of audible noise.) + The "alert" character, `Ctrl-g', ASCII code 7 (BEL). (This often + makes some sort of audible noise.) `\b' Backspace, `Ctrl-h', ASCII code 8 (BS). @@ -3216,26 +3351,34 @@ apply to both string constants and regexp constants: `\xHH...' The hexadecimal value HH, where HH stands for a sequence of - hexadecimal digits (`0'-`9', and either `A'-`F' or `a'-`f'). Like - the same construct in ISO C, the escape sequence continues until - the first nonhexadecimal digit is seen. (c.e.) However, using - more than two hexadecimal digits produces undefined results. (The - `\x' escape sequence is not allowed in POSIX `awk'.) + hexadecimal digits (`0'-`9', and either `A'-`F' or `a'-`f'). A + maximum of two digts are allowed after the `\x'. Any further + hexadecimal digits are treated as simple letters or numbers. + (c.e.) + + CAUTION: In ISO C, the escape sequence continues until the + first nonhexadecimal digit is seen. For many years, `gawk' + would continue incorporating hexadecimal digits into the + value until a non-hexadecimal digit or the end of the string + was encountered. However, using more than two hexadecimal + digits produces `\/' A literal slash (necessary for regexp constants only). This sequence is used when you want to write a regexp constant that - contains a slash. Because the regexp is delimited by slashes, you - need to escape the slash that is part of the pattern, in order to + contains a slash (such as `/.*:\/home\/[[:alnum:]]+:.*/'; the + `[[:alnum:]]' notation is discussed shortly, in *note Bracket + Expressions::). Because the regexp is delimited by slashes, you + need to escape any slash that is part of the pattern, in order to tell `awk' to keep processing the rest of the regexp. `\"' A literal double quote (necessary for string constants only). This sequence is used when you want to write a string constant - that contains a double quote. Because the string is delimited by - double quotes, you need to escape the quote that is part of the - string, in order to tell `awk' to keep processing the rest of the - string. + that contains a double quote (such as `"He said \"hi!\" to her."'). + Because the string is delimited by double quotes, you need to + escape any quote that is part of the string, in order to tell + `awk' to keep processing the rest of the string. In `gawk', a number of additional two-character sequences that begin with a backslash have special meaning in regexps. *Note GNU Regexp @@ -3270,12 +3413,12 @@ is not one of the characters previously listed, POSIX `awk' purposely leaves what happens as undefined. There are two choices: Strip the backslash out - This is what Brian Kernighan's `awk' and `gawk' both do. For - example, `"a\qc"' is the same as `"aqc"'. (Because this is such - an easy bug both to introduce and to miss, `gawk' warns you about - it.) Consider `FS = "[ \t]+\|[ \t]+"' to use vertical bars - surrounded by whitespace as the field separator. There should be - two backslashes in the string: `FS = "[ \t]+\\|[ \t]+"'.) + This is what BWK `awk' and `gawk' both do. For example, `"a\qc"' + is the same as `"aqc"'. (Because this is such an easy bug both to + introduce and to miss, `gawk' warns you about it.) Consider `FS = + "[ \t]+\|[ \t]+"' to use vertical bars surrounded by whitespace as + the field separator. There should be two backslashes in the + string: `FS = "[ \t]+\\|[ \t]+"'.) Leave the backslash alone Some other `awk' implementations do this. In such @@ -3324,20 +3467,21 @@ sequences and that are not listed in the table stand for themselves: at the beginning of the string. It is important to realize that `^' does not match the beginning of - a line embedded in a string. The condition is not true in the - following example: + a line (the point right after a `\n' newline character) embedded + in a string. The condition is not true in the following example: if ("line1\nLINE 2" ~ /^L/) ... `$' This is similar to `^', but it matches only at the end of a string. For example, `p$' matches a record that ends with a `p'. The `$' - is an anchor and does not match the end of a line embedded in a - string. The condition in the following example is not true: + is an anchor and does not match the end of a line (the point right + before a `\n' newline character) embedded in a string. The + condition in the following example is not true: if ("line1\nLINE 2" ~ /1$/) ... -`. (period)' +`.' (period) This matches any single character, _including_ the newline character. For example, `.P' matches any single character followed by a `P' in a string. Using concatenation, we can make a @@ -3349,7 +3493,7 @@ sequences and that are not listed in the table stand for themselves: Otherwise, NUL is just another character. Other versions of `awk' may not be able to match the NUL character. -`[...]' +`['...`]' This is called a "bracket expression".(1) It matches any _one_ of the characters that are enclosed in the square brackets. For example, `[MVX]' matches any one of the characters `M', `V', or @@ -3357,7 +3501,7 @@ sequences and that are not listed in the table stand for themselves: square brackets of a bracket expression is given in *note Bracket Expressions::. -`[^ ...]' +`[^'...`]' This is a "complemented bracket expression". The first character after the `[' _must_ be a `^'. It matches any characters _except_ those in the square brackets. For example, `[^awk]' matches any @@ -3366,14 +3510,15 @@ sequences and that are not listed in the table stand for themselves: `|' This is the "alternation operator" and it is used to specify alternatives. The `|' has the lowest precedence of all the regular - expression operators. For example, `^P|[[:digit:]]' matches any - string that matches either `^P' or `[[:digit:]]'. This means it - matches any string that starts with `P' or contains a digit. + expression operators. For example, `^P|[aeiouy]' matches any + string that matches either `^P' or `[aeiouy]'. This means it + matches any string that starts with `P' or contains (anywhere + within it) a lowercase English vowel. The alternation applies to the largest possible regexps on either side. -`(...)' +`('...`)' Parentheses are used for grouping in regular expressions, as in arithmetic. They can be used to concatenate regular expressions containing the alternation operator, `|'. For example, @@ -3388,31 +3533,29 @@ sequences and that are not listed in the table stand for themselves: matches of one `p' followed by any number of `h's. This also matches just `p' if no `h's are present. - The `*' repeats the _smallest_ possible preceding expression. - (Use parentheses if you want to repeat a larger expression.) It - finds as many repetitions as possible. For example, `awk - '/\(c[ad][ad]*r x\)/ { print }' sample' prints every record in - `sample' containing a string of the form `(car x)', `(cdr x)', - `(cadr x)', and so on. Notice the escaping of the parentheses by - preceding them with backslashes. + There are two subtle points to understand about how `*' works. + First, the `*' applies only to the single preceding regular + expression component (e.g., in `ph*', it applies just to the `h'). + To cause `*' to apply to a larger sub-expression, use parentheses: + `(ph)*' matches `ph', `phph', `phphph' and so on. + + Second, `*' finds as many repetititons as possible. If the text to + be matched is `phhhhhhhhhhhhhhooey', `ph*' matches all of the `h's. `+' This symbol is similar to `*', except that the preceding expression must be matched at least once. This means that `wh+y' would match `why' and `whhy', but not `wy', whereas `wh*y' would - match all three of these strings. The following is a simpler way - of writing the last `*' example: - - awk '/\(c[ad]+r x\)/ { print }' sample + match all three. `?' This symbol is similar to `*', except that the preceding expression can be matched either once or not at all. For example, `fe?d' matches `fed' and `fd', but nothing else. -`{N}' -`{N,}' -`{N,M}' +`{'N`}' +`{'N`,}' +`{'N`,'M`}' One or two numbers inside braces denote an "interval expression". If there is one number in the braces, the preceding regexp is repeated N times. If there are two numbers separated by a comma, @@ -3473,7 +3616,7 @@ list". regexp operator or function. -File: gawk.info, Node: Bracket Expressions, Next: GNU Regexp Operators, Prev: Regexp Operators, Up: Regexp +File: gawk.info, Node: Bracket Expressions, Next: Leftmost Longest, Prev: Regexp Operators, Up: Regexp 3.4 Using Bracket Expressions ============================= @@ -3494,7 +3637,9 @@ expression, put a `\' in front of it. For example: [d\]] -matches either `d' or `]'. +matches either `d' or `]'. Additionally, if you place `]' right after +the opening `[', the closing bracket is treated as one of the +characters to be matched. This treatment of `\' in bracket expressions is compatible with other `awk' implementations and is also mandated by POSIX. The regular @@ -3541,6 +3686,14 @@ set had other alphabetic characters in it, this would not match them. With the POSIX character classes, you can write `/[[:alnum:]]/' to match the alphabetic and numeric characters in your character set. + Some utilities that match regular expressions provide a non-standard +`[:ascii:]' character class; `awk' does not. However, you can simulate +such a construct using `[\x00-\x7F]'. This matches all values +numerically between zero and 127, which is the defined range of the +ASCII character set. Use a complemented character list +(`[^\x00-\x7F]') to match any single-byte characters that are not in +the ASCII range. + Two additional special sequences can appear in bracket expressions. These apply to non-ASCII character sets, which can have single symbols (called "collating elements") that are represented with more than one @@ -3568,9 +3721,118 @@ Equivalence classes classes. -File: gawk.info, Node: GNU Regexp Operators, Next: Case-sensitivity, Prev: Bracket Expressions, Up: Regexp +File: gawk.info, Node: Leftmost Longest, Next: Computed Regexps, Prev: Bracket Expressions, Up: Regexp + +3.5 How Much Text Matches? +========================== + +Consider the following: + + echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' + + This example uses the `sub()' function (which we haven't discussed +yet; *note String Functions::) to make a change to the input record. +Here, the regexp `/a+/' indicates "one or more `a' characters," and the +replacement text is `<A>'. + + The input contains four `a' characters. `awk' (and POSIX) regular +expressions always match the leftmost, _longest_ sequence of input +characters that can match. Thus, all four `a' characters are replaced +with `<A>' in this example: + + $ echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' + -| <A>bcd + + For simple match/no-match tests, this is not so important. But when +doing text matching and substitutions with the `match()', `sub()', +`gsub()', and `gensub()' functions, it is very important. *Note String +Functions::, for more information on these functions. Understanding +this principle is also important for regexp-based record and field +splitting (*note Records::, and also *note Field Separators::). + + +File: gawk.info, Node: Computed Regexps, Next: GNU Regexp Operators, Prev: Leftmost Longest, Up: Regexp + +3.6 Using Dynamic Regexps +========================= + +The righthand side of a `~' or `!~' operator need not be a regexp +constant (i.e., a string of characters between slashes). It may be any +expression. The expression is evaluated and converted to a string if +necessary; the contents of the string are then used as the regexp. A +regexp computed in this way is called a "dynamic regexp" or a "computed +regexp": + + BEGIN { digits_regexp = "[[:digit:]]+" } + $0 ~ digits_regexp { print } + +This sets `digits_regexp' to a regexp that describes one or more digits, +and tests whether the input record matches this regexp. + + NOTE: When using the `~' and `!~' operators, there is a difference + between a regexp constant enclosed in slashes and a string + constant enclosed in double quotes. If you are going to use a + string constant, you have to understand that the string is, in + essence, scanned _twice_: the first time when `awk' reads your + program, and the second time when it goes to match the string on + the lefthand side of the operator with the pattern on the right. + This is true of any string-valued expression (such as + `digits_regexp', shown previously), not just string constants. + + What difference does it make if the string is scanned twice? The +answer has to do with escape sequences, and particularly with +backslashes. To get a backslash into a regular expression inside a +string, you have to type two backslashes. + + For example, `/\*/' is a regexp constant for a literal `*'. Only +one backslash is needed. To do the same thing with a string, you have +to type `"\\*"'. The first backslash escapes the second one so that +the string actually contains the two characters `\' and `*'. + + Given that you can use both regexp and string constants to describe +regular expressions, which should you use? The answer is "regexp +constants," for several reasons: + + * String constants are more complicated to write and more difficult + to read. Using regexp constants makes your programs less + error-prone. Not understanding the difference between the two + kinds of constants is a common source of errors. + + * It is more efficient to use regexp constants. `awk' can note that + you have supplied a regexp and store it internally in a form that + makes pattern matching more efficient. When using a string + constant, `awk' must first convert the string into this internal + form and then perform the pattern matching. + + * Using regexp constants is better form; it shows clearly that you + intend a regexp match. + + Using `\n' in Bracket Expressions of Dynamic Regexps + + Some versions of `awk' do not allow the newline character to be used +inside a bracket expression for a dynamic regexp: -3.5 `gawk'-Specific Regexp Operators + $ awk '$0 ~ "[ \t\n]"' + error--> awk: newline in character class [ + error--> ]... + error--> source line number 1 + error--> context is + error--> >>> <<< + + But a newline in a regexp constant works with no problem: + + $ awk '$0 ~ /[ \t\n]/' + here is a sample line + -| here is a sample line + Ctrl-d + + `gawk' does not have this problem, and it isn't likely to occur +often in practice, but it's worth noting for future reference. + + +File: gawk.info, Node: GNU Regexp Operators, Next: Case-sensitivity, Prev: Computed Regexps, Up: Regexp + +3.7 `gawk'-Specific Regexp Operators ==================================== GNU software that deals with regular expressions provides a number of @@ -3654,9 +3916,9 @@ No options Traditional Unix `awk' regexps are matched. The GNU operators are not special, and interval expressions are not available. The POSIX character classes (`[[:alnum:]]', etc.) are supported, as - Brian Kernighan's `awk' does support them. Characters described - by octal and hexadecimal escape sequences are treated literally, - even if they represent regexp metacharacters. + BWK `awk' does support them. Characters described by octal and + hexadecimal escape sequences are treated literally, even if they + represent regexp metacharacters. `--re-interval' Allow interval expressions in regexps, if `--traditional' has been @@ -3664,9 +3926,9 @@ No options default. -File: gawk.info, Node: Case-sensitivity, Next: Leftmost Longest, Prev: GNU Regexp Operators, Up: Regexp +File: gawk.info, Node: Case-sensitivity, Next: Regexp Summary, Prev: GNU Regexp Operators, Up: Regexp -3.6 Case Sensitivity in Matching +3.8 Case Sensitivity in Matching ================================ Case is normally significant in regular expressions, both when matching @@ -3692,7 +3954,9 @@ works in any POSIX-compliant `awk'. Another method, specific to `gawk', is to set the variable `IGNORECASE' to a nonzero value (*note Built-in Variables::). When `IGNORECASE' is not zero, _all_ regexp and string operations ignore -case. Changing the value of `IGNORECASE' dynamically controls the +case. + + Changing the value of `IGNORECASE' dynamically controls the case-sensitivity of the program as it runs. Case is significant by default because `IGNORECASE' (like most variables) is initialized to zero: @@ -3715,9 +3979,6 @@ dynamically turn case-sensitivity on or off for all the rules at once. `IGNORECASE' from the command line is a way to make a program case-insensitive without having to edit it. - Both regexp and string comparison operations are affected by -`IGNORECASE'. - In multibyte locales, the equivalences between upper- and lowercase characters are tested based on the wide-character values of the locale's character set. Otherwise, the characters are tested based on @@ -3740,112 +4001,42 @@ obscure and we don't recommend it. means that `gawk' does the right thing. -File: gawk.info, Node: Leftmost Longest, Next: Computed Regexps, Prev: Case-sensitivity, Up: Regexp - -3.7 How Much Text Matches? -========================== +File: gawk.info, Node: Regexp Summary, Prev: Case-sensitivity, Up: Regexp -Consider the following: - - echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' - - This example uses the `sub()' function (which we haven't discussed -yet; *note String Functions::) to make a change to the input record. -Here, the regexp `/a+/' indicates "one or more `a' characters," and the -replacement text is `<A>'. - - The input contains four `a' characters. `awk' (and POSIX) regular -expressions always match the leftmost, _longest_ sequence of input -characters that can match. Thus, all four `a' characters are replaced -with `<A>' in this example: - - $ echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' - -| <A>bcd - - For simple match/no-match tests, this is not so important. But when -doing text matching and substitutions with the `match()', `sub()', -`gsub()', and `gensub()' functions, it is very important. *Note String -Functions::, for more information on these functions. Understanding -this principle is also important for regexp-based record and field -splitting (*note Records::, and also *note Field Separators::). - - -File: gawk.info, Node: Computed Regexps, Prev: Leftmost Longest, Up: Regexp - -3.8 Using Dynamic Regexps -========================= - -The righthand side of a `~' or `!~' operator need not be a regexp -constant (i.e., a string of characters between slashes). It may be any -expression. The expression is evaluated and converted to a string if -necessary; the contents of the string are then used as the regexp. A -regexp computed in this way is called a "dynamic regexp": - - BEGIN { digits_regexp = "[[:digit:]]+" } - $0 ~ digits_regexp { print } - -This sets `digits_regexp' to a regexp that describes one or more digits, -and tests whether the input record matches this regexp. - - NOTE: When using the `~' and `!~' operators, there is a difference - between a regexp constant enclosed in slashes and a string - constant enclosed in double quotes. If you are going to use a - string constant, you have to understand that the string is, in - essence, scanned _twice_: the first time when `awk' reads your - program, and the second time when it goes to match the string on - the lefthand side of the operator with the pattern on the right. - This is true of any string-valued expression (such as - `digits_regexp', shown previously), not just string constants. - - What difference does it make if the string is scanned twice? The -answer has to do with escape sequences, and particularly with -backslashes. To get a backslash into a regular expression inside a -string, you have to type two backslashes. - - For example, `/\*/' is a regexp constant for a literal `*'. Only -one backslash is needed. To do the same thing with a string, you have -to type `"\\*"'. The first backslash escapes the second one so that -the string actually contains the two characters `\' and `*'. +3.9 Summary +=========== - Given that you can use both regexp and string constants to describe -regular expressions, which should you use? The answer is "regexp -constants," for several reasons: + * Regular expressions describe sets of strings to be matched. In + `awk', regular expression constants are written enclosed between + slashes: `/'...`/'. - * String constants are more complicated to write and more difficult - to read. Using regexp constants makes your programs less - error-prone. Not understanding the difference between the two - kinds of constants is a common source of errors. - - * It is more efficient to use regexp constants. `awk' can note that - you have supplied a regexp and store it internally in a form that - makes pattern matching more efficient. When using a string - constant, `awk' must first convert the string into this internal - form and then perform the pattern matching. + * Regexp constants may be used standalone in patterns and in + conditional expressions, or as part of matching expressions using + the `~' and `!~' operators. - * Using regexp constants is better form; it shows clearly that you - intend a regexp match. + * Escape sequences let you represent non-printable characters and + also let you represent regexp metacharacters as literal characters + to be matched. - Using `\n' in Bracket Expressions of Dynamic Regexps + * Regexp operators provide grouping, alternation and repetition. - Some commercial versions of `awk' do not allow the newline character -to be used inside a bracket expression for a dynamic regexp: + * Bracket expressions give you a shorthand for specifying sets of + characters that can match at a particular point in a regexp. + Within bracket expressions, POSIX character classes let you specify + certain groups of characters in a locale-independent fashion. - $ awk '$0 ~ "[ \t\n]"' - error--> awk: newline in character class [ - error--> ]... - error--> source line number 1 - error--> context is - error--> >>> <<< + * `gawk''s `IGNORECASE' variable lets you control the case + sensitivity of regexp matching. In other `awk' versions, use + `tolower()' or `toupper()'. - But a newline in a regexp constant works with no problem: + * Regular expressions match the leftmost longest text in the string + being matched. This matters for cases where you need to know the + extent of the match, such as for text substitution and when the + record separator is a regexp. - $ awk '$0 ~ /[ \t\n]/' - here is a sample line - -| here is a sample line - Ctrl-d + * Matching expressions may use dynamic regexps, that is, string + values treated as regular expressions. - `gawk' does not have this problem, and it isn't likely to occur -often in practice, but it's worth noting for future reference. File: gawk.info, Node: Reading Files, Next: Printing, Prev: Regexp, Up: Top @@ -3885,8 +4076,10 @@ have to be named on the `awk' command line (*note Getline::). * Getline:: Reading files under explicit program control using the `getline' function. * Read Timeout:: Reading input with a timeout. -* Command line directories:: What happens if you put a directory on the +* Command-line directories:: What happens if you put a directory on the command line. +* Input Summary:: Input summary. +* Input Exercises:: Exercises. File: gawk.info, Node: Records, Next: Fields, Up: Reading Files @@ -3894,16 +4087,27 @@ File: gawk.info, Node: Records, Next: Fields, Up: Reading Files 4.1 How Input Is Split into Records =================================== -The `awk' utility divides the input for your `awk' program into records -and fields. `awk' keeps track of the number of records that have been -read so far from the current input file. This value is stored in a -built-in variable called `FNR'. It is reset to zero when a new file is -started. Another built-in variable, `NR', records the total number of -input records read so far from all data files. It starts at zero, but -is never automatically reset to zero. +`awk' divides the input for your program into records and fields. It +keeps track of the number of records that have been read so far from +the current input file. This value is stored in a built-in variable +called `FNR' which is reset to zero when a new file is started. +Another built-in variable, `NR', records the total number of input +records read so far from all data files. It starts at zero, but is +never automatically reset to zero. + +* Menu: + +* awk split records:: How standard `awk' splits records. +* gawk split records:: How `gawk' splits records. - Records are separated by a character called the "record separator". -By default, the record separator is the newline character. This is why + +File: gawk.info, Node: awk split records, Next: gawk split records, Up: Records + +4.1.1 Record Splitting With Standard `awk' +------------------------------------------ + +Records are separated by a character called the "record separator". By +default, the record separator is the newline character. This is why records are, by default, single lines. A different character can be used for the record separator by assigning the character to the built-in variable `RS'. @@ -4023,16 +4227,22 @@ affected. After the end of the record has been determined, `gawk' sets the variable `RT' to the text in the input that matched `RS'. - When using `gawk', the value of `RS' is not limited to a -one-character string. It can be any regular expression (*note -Regexp::). (c.e.) In general, each record ends at the next string that -matches the regular expression; the next record starts at the end of -the matching string. This general rule is actually at work in the -usual case, where `RS' contains just a newline: a record ends at the -beginning of the next matching string (the next newline in the input), -and the following record starts just after the end of this string (at -the first character of the following line). The newline, because it -matches `RS', is not part of either record. + +File: gawk.info, Node: gawk split records, Prev: awk split records, Up: Records + +4.1.2 Record Splitting With `gawk' +---------------------------------- + +When using `gawk', the value of `RS' is not limited to a one-character +string. It can be any regular expression (*note Regexp::). (c.e.) In +general, each record ends at the next string that matches the regular +expression; the next record starts at the end of the matching string. +This general rule is actually at work in the usual case, where `RS' +contains just a newline: a record ends at the beginning of the next +matching string (the next newline in the input), and the following +record starts just after the end of this string (at the first character +of the following line). The newline, because it matches `RS', is not +part of either record. When `RS' is a single character, `RT' contains the same single character. However, when `RS' is a regular expression, `RT' contains @@ -4048,16 +4258,16 @@ trailing whitespace: $ echo record 1 AAAA record 2 BBBB record 3 | > gawk 'BEGIN { RS = "\n|( *[[:upper:]]+ *)" } - > { print "Record =", $0, "and RT =", RT }' - -| Record = record 1 and RT = AAAA - -| Record = record 2 and RT = BBBB - -| Record = record 3 and RT = - -| + > { print "Record =", $0,"and RT = [" RT "]" }' + -| Record = record 1 and RT = [ AAAA ] + -| Record = record 2 and RT = [ BBBB ] + -| Record = record 3 and RT = [ + -| ] -The final line of output has an extra blank line. This is because the -value of `RT' is a newline, and the `print' statement supplies its own -terminating newline. *Note Simple Sed::, for a more useful example of -`RS' as a regexp and `RT'. +The square brackets delineate the contents of `RT', letting you see the +leading and trailing whitespace. The final value of `RT' `RT' is a +newline. *Note Simple Sed::, for a more useful example of `RS' as a +regexp and `RT'. If you set `RS' to a regular expression that allows optional trailing text, such as `RS = "abc(XYZ)?"' it is possible, due to @@ -4095,8 +4305,10 @@ use for `RS' in this case: BEGIN { RS = "\0" } # whole file becomes one record? `gawk' in fact accepts this, and uses the NUL character for the -record separator. However, this usage is _not_ portable to most other -`awk' implementations. +record separator. This works for certain special files, such as +`/proc/environ' on GNU/Linux systems, where the NUL character is in +fact the record separator. However, this usage is _not_ portable to +most other `awk' implementations. Almost all other `awk' implementations(1) store strings internally as C-style strings. C strings use the NUL character as the string @@ -4107,10 +4319,9 @@ terminator. In effect, this means that `RS = "\0"' is the same as `RS as a record separator. However, this is a special case: `mawk' does not allow embedded NUL characters in strings. - The best way to treat a whole file as a single record is to simply -read the file in, one record at a time, concatenating each record onto -the end of the previous ones. - + *Note Readfile Function::, for an interesting, portable way to read +whole files. If you are using `gawk', see *note Extension Sample +Readfile::, for another option. ---------- Footnotes ---------- @@ -4135,7 +4346,7 @@ to these pieces of the record. You don't have to use them--you can operate on the whole record if you want--but fields are what make simple `awk' programs so powerful. - A dollar-sign (`$') is used to refer to a field in an `awk' program, + You use a dollar-sign (`$') to refer to a field in an `awk' program, followed by the number of the field you want. Thus, `$1' refers to the first field, `$2' to the second, and so on. (Unlike the Unix shells, the field numbers are not limited to single digits. `$127' is the one @@ -4158,8 +4369,9 @@ the last one (such as `$8' when the record has only seven fields), you get the empty string. (If used in a numeric operation, you get zero.) The use of `$0', which looks like a reference to the "zero-th" -field, is a special case: it represents the whole input record when you -are not interested in specific fields. Here are some more examples: +field, is a special case: it represents the whole input record. Use it +when you are not interested in specific fields. Here are some more +examples: $ awk '$1 ~ /li/ { print $0 }' mail-list -| Amelia 555-5553 amelia.zodiacusque@gmail.com F @@ -4191,11 +4403,11 @@ File: gawk.info, Node: Nonconstant Fields, Next: Changing Fields, Prev: Field 4.3 Nonconstant Field Numbers ============================= -The number of a field does not need to be a constant. Any expression in -the `awk' language can be used after a `$' to refer to a field. The -value of the expression specifies the field number. If the value is a -string, rather than a number, it is converted to a number. Consider -this example: +A field number need not be a constant. Any expression in the `awk' +language can be used after a `$' to refer to a field. The value of the +expression specifies the field number. If the value is a string, +rather than a number, it is converted to a number. Consider this +example: awk '{ print $NR }' @@ -4212,7 +4424,7 @@ another example of using expressions as field numbers: number of the field to print. The `*' sign represents multiplication, so the expression `2*2' evaluates to four. The parentheses are used so that the multiplication is done before the `$' operation; they are -necessary whenever there is a binary operator in the field-number +necessary whenever there is a binary operator(1) in the field-number expression. This example, then, prints the type of relationship (the fourth field) for every line of the file `mail-list'. (All of the `awk' operators are listed, in order of decreasing precedence, in *note @@ -4231,6 +4443,12 @@ Variables::). The expression `$NF' is not a special feature--it is the direct consequence of evaluating `NF' and using its value as a field number. + ---------- Footnotes ---------- + + (1) A "binary operator", such as `*' for multiplication, is one that +takes two operands. The distinction is required, since `awk' also has +unary (one-operand) and ternary (three-operand) operators. + File: gawk.info, Node: Changing Fields, Next: Field Separators, Prev: Nonconstant Fields, Up: Reading Files @@ -4256,11 +4474,11 @@ three minus ten: `$3 - 10'. (*Note Arithmetic Ops::.) Then it prints the original and new values for field three. (Someone in the warehouse made a consistent mistake while inventorying the red boxes.) - For this to work, the text in field `$3' must make sense as a -number; the string of characters must be converted to a number for the -computer to do arithmetic on it. The number resulting from the -subtraction is converted back to a string of characters that then -becomes field three. *Note Conversion::. + For this to work, the text in `$3' must make sense as a number; the +string of characters must be converted to a number for the computer to +do arithmetic on it. The number resulting from the subtraction is +converted back to a string of characters that then becomes field three. +*Note Conversion::. When the value of a field is changed (as perceived by `awk'), the text of the input record is recalculated to contain the new field where @@ -4325,7 +4543,7 @@ even when you assign the empty string to a field. For example: -| a::c:d -| 4 -The field is still there; it just has an empty value, denoted by the +The field is still there; it just has an empty value, delimited by the two colons between `a' and `c'. This example shows what happens if you create a new field: @@ -4391,7 +4609,7 @@ File: gawk.info, Node: Field Separators, Next: Constant Size, Prev: Changing * Default Field Splitting:: How fields are normally separated. * Regexp Field Splitting:: Using regexps as the field separator. * Single Character Fields:: Making each character a separate field. -* Command Line Field Separator:: Setting `FS' from the command-line. +* Command Line Field Separator:: Setting `FS' from the command line. * Full Line Fields:: Making the full line be a single field. * Field Splitting Summary:: Some final points and a summary table. @@ -4511,7 +4729,7 @@ letter): > { print $2 }' -| a -In this case, the first field is "null" or empty. +In this case, the first field is null, or empty. The stripping of leading and trailing whitespace also comes into play whenever `$0' is recomputed. For instance, study this pipeline: @@ -4535,9 +4753,8 @@ field separator a new string? It turns out that different `awk' versions answer this question differently, and you should not rely on any specific behavior in your programs. (d.c.) - As a point of information, Brian Kernighan's `awk' allows `^' to -match only at the beginning of the record. `gawk' also works this way. -For example: + As a point of information, BWK `awk' allows `^' to match only at the +beginning of the record. `gawk' also works this way. For example: $ echo 'xxAA xxBxx C' | > gawk -F '(^x+)|( +)' '{ for (i = 1; i <= NF; i++) @@ -4610,7 +4827,8 @@ argument to `-F' is `t', then `FS' is set to the TAB character. If you type `-F\t' at the shell, without any quotes, the `\' gets deleted, so `awk' figures that you really want your fields to be separated with TABs and not `t's. Use `-v FS="t"' or `-F"[t]"' on the command line if -you really do want to separate your fields with `t's. +you really do want to separate your fields with `t's. Use `-F '\t'' +when not in compatibility mode to specify that TABs separate fields. As an example, let's use an `awk' program file called `edu.awk' that contains the pattern `/edu/' and the action `print $1': @@ -4730,8 +4948,8 @@ which usually prints: root -on an incorrect implementation of `awk', while `gawk' prints something -like: +on an incorrect implementation of `awk', while `gawk' prints the full +first line of the file, something like: root:nSijPlPhZZwgE:0:0:Root:/: @@ -4811,7 +5029,7 @@ calculated idle time: BEGIN { FIELDWIDTHS = "9 6 10 6 7 7 35" } NR > 2 { idle = $4 - sub(/^ */, "", idle) # strip leading spaces + sub(/^ +/, "", idle) # strip leading spaces if (idle == "") idle = 0 if (idle ~ /:/) { @@ -4942,15 +5160,17 @@ would be to remove the quotes when they occur, with something like this: As with `FS', the `IGNORECASE' variable (*note User-modified::) affects field splitting with `FPAT'. - Similar to `FIELDWIDTHS', the value of `PROCINFO["FS"]' will be -`"FPAT"' if content-based field splitting is being used. + Assigning a value to `FPAT' overrides field splitting with `FS' and +with `FIELDWIDTHS'. Similar to `FIELDWIDTHS', the value of +`PROCINFO["FS"]' will be `"FPAT"' if content-based field splitting is +being used. NOTE: Some programs export CSV data that contains embedded newlines between the double quotes. `gawk' provides no way to deal with this. Since there is no formal specification for CSV data, there isn't much more to be done; the `FPAT' mechanism provides an elegant solution for the majority of cases, and the - `gawk' maintainer is satisfied with that. + `gawk' developers are satisfied with that. As written, the regexp used for `FPAT' requires that each field have a least one character. A straightforward modification (changing @@ -4961,6 +5181,11 @@ changed the first `+' to `*') allows fields to be empty: Finally, the `patsplit()' function makes the same functionality available for splitting regular strings (*note String Functions::). + To recap, `gawk' provides three independent methods to split input +records into fields. `gawk' uses whichever mechanism was last chosen +based on which of the three variables--`FS', `FIELDWIDTHS', and +`FPAT'--was last assigned to. + ---------- Footnotes ---------- (1) At least, we don't know of one. @@ -5000,8 +5225,8 @@ doesn't start until the first nonblank line that follows--no matter how many blank lines appear in a row, they are considered one record separator. - There is an important difference between `RS = ""' and `RS = -"\n\n+"'. In the first case, leading newlines in the input data file + However, there is an important difference between `RS = ""' and `RS += "\n\n+"'. In the first case, leading newlines in the input data file are ignored, and if a file ends without extra blank lines after the last record, the final newline is removed from the record. In the second case, this special processing is not done. (d.c.) @@ -5111,7 +5336,7 @@ File: gawk.info, Node: Getline, Next: Read Timeout, Prev: Multiple Line, Up: ================================= So far we have been getting our input data from `awk''s main input -stream--either the standard input (usually your terminal, sometimes the +stream--either the standard input (usually your keyboard, sometimes the output from another program) or from the files specified on the command line. The `awk' language has a special built-in command called `getline' that can be used to read input under your explicit control. @@ -5123,8 +5348,8 @@ yet. Therefore, come back and study the `getline' command _after_ you have reviewed the rest of this Info file and have a good knowledge of how `awk' works. - The `getline' command returns one if it finds a record and zero if -it encounters the end of the file. If there is some error in getting a + The `getline' command returns 1 if it finds a record and 0 if it +encounters the end of the file. If there is some error in getting a record, such as a file that cannot be opened, then `getline' returns -1. In this case, `gawk' sets the variable `ERRNO' to a string describing the error that occurred. @@ -5163,35 +5388,47 @@ input record and split it up into fields. This is useful if you've finished processing the current record, but want to do some special processing on the next record _right now_. For example: + # Remove text between /* and */, inclusive { - if ((t = index($0, "/*")) != 0) { - # value of `tmp' will be "" if t is 1 - tmp = substr($0, 1, t - 1) - u = index(substr($0, t + 2), "*/") - offset = t + 2 - while (u == 0) { - if (getline <= 0) { + if ((i = index($0, "/*")) != 0) { + out = substr($0, 1, i - 1) # leading part of the string + rest = substr($0, i + 2) # ... */ ... + j = index(rest, "*/") # is */ in trailing part? + if (j > 0) { + rest = substr(rest, j + 2) # remove comment + } else { + while (j == 0) { + # get more text + if (getline <= 0) { m = "unexpected EOF or error" m = (m ": " ERRNO) print m > "/dev/stderr" exit - } - u = index($0, "*/") - offset = 0 - } - # substr() expression will be "" if */ - # occurred at end of line - $0 = tmp substr($0, offset + u + 2) - } - print $0 + } + # build up the line using string concatenation + rest = rest $0 + j = index(rest, "*/") # is */ in trailing part? + if (j != 0) { + rest = substr(rest, j + 2) + break + } + } + } + # build up the output line using string concatenation + $0 = out rest + } + print $0 } This `awk' program deletes C-style comments (`/* ... */') from the -input. By replacing the `print $0' with other statements, you could -perform more complicated processing on the decommented input, such as -searching for matches of a regular expression. (This program has a -subtle problem--it does not work if one comment ends and another begins -on the same line.) +input. It uses a number of features we haven't covered yet, including +string concatenation (*note Concatenation::) and the `index()' and +`substr()' built-in functions (*note String Functions::). By replacing +the `print $0' with other statements, you could perform more +complicated processing on the decommented input, such as searching for +matches of a regular expression. (This program has a subtle +problem--it does not work if one comment ends and another begins on the +same line.) This form of the `getline' command sets `NF', `NR', `FNR', `RT', and the value of `$0'. @@ -5273,9 +5510,9 @@ are changed, resulting in a new value of `NF'. `RT' is also set. According to POSIX, `getline < EXPRESSION' is ambiguous if EXPRESSION contains unparenthesized operators other than `$'; for example, `getline < dir "/" file' is ambiguous because the -concatenation operator is not parenthesized. You should write it as -`getline < (dir "/" file)' if you want your program to be portable to -all `awk' implementations. +concatenation operator (not discussed yet; *note Concatenation::) is +not parenthesized. You should write it as `getline < (dir "/" file)' if +you want your program to be portable to all `awk' implementations. File: gawk.info, Node: Getline/Variable/File, Next: Getline/Pipe, Prev: Getline/File, Up: Getline @@ -5386,10 +5623,10 @@ all `awk' implementations. NOTE: Unfortunately, `gawk' has not been consistent in its treatment of a construct like `"echo " "date" | getline'. Most versions, including the current version, treat it at as `("echo " - "date") | getline'. (This how Brian Kernighan's `awk' behaves.) - Some versions changed and treated it as `"echo " ("date" | - getline)'. (This is how `mawk' behaves.) In short, _always_ use - explicit parentheses, and then you won't have to worry. + "date") | getline'. (This how BWK `awk' behaves.) Some versions + changed and treated it as `"echo " ("date" | getline)'. (This is + how `mawk' behaves.) In short, _always_ use explicit parentheses, + and then you won't have to worry. File: gawk.info, Node: Getline/Variable/Pipe, Next: Getline/Coprocess, Prev: Getline/Pipe, Up: Getline @@ -5480,10 +5717,10 @@ in mind: testing the new record against every pattern. However, the new record is tested against any subsequent rules. - * Many `awk' implementations limit the number of pipelines that an - `awk' program may have open to just one. In `gawk', there is no - such limit. You can open as many pipelines (and coprocesses) as - the underlying operating system permits. + * Some very old `awk' implementations limit the number of pipelines + that an `awk' program may have open to just one. In `gawk', there + is no such limit. You can open as many pipelines (and + coprocesses) as the underlying operating system permits. * An interesting side effect occurs if you use `getline' without a redirection inside a `BEGIN' rule. Because an unredirected @@ -5522,9 +5759,9 @@ in mind: file is encountered, before the element in `a' is assigned? `gawk' treats `getline' like a function call, and evaluates the - expression `a[++c]' before attempting to read from `f'. Other - versions of `awk' only evaluate the expression once they know that - there is a string value to be assigned. Caveat Emptor. + expression `a[++c]' before attempting to read from `f'. However, + some versions of `awk' only evaluate the expression once they know + that there is a string value to be assigned. Caveat Emptor. File: gawk.info, Node: Getline Summary, Prev: Getline Notes, Up: Getline @@ -5555,15 +5792,17 @@ VAR Table 4.1: `getline' Variants and What They Set -File: gawk.info, Node: Read Timeout, Next: Command line directories, Prev: Getline, Up: Reading Files +File: gawk.info, Node: Read Timeout, Next: Command-line directories, Prev: Getline, Up: Reading Files 4.10 Reading Input With A Timeout ================================= -You may specify a timeout in milliseconds for reading input from a -terminal, pipe or two-way communication including, TCP/IP sockets. This -can be done on a per input, command or connection basis, by setting a -special element in the `PROCINFO' array: +This minor node describes a feature that is specific to `gawk'. + + You may specify a timeout in milliseconds for reading input from the +keyboard, a pipe, or two-way communication, including TCP/IP sockets. +This can be done on a per input, command or connection basis, by +setting a special element in the `PROCINFO' (*note Auto-set::) array: PROCINFO["input_name", "READ_TIMEOUT"] = TIMEOUT IN MILLISECONDS @@ -5579,19 +5818,19 @@ from the server after a certain amount of time: else if (ERRNO != "") print ERRNO - Here is how to read interactively from the terminal(1) without -waiting for more than five seconds: + Here is how to read interactively from the user(1) without waiting +for more than five seconds: PROCINFO["/dev/stdin", "READ_TIMEOUT"] = 5000 while ((getline < "/dev/stdin") > 0) print $0 - `gawk' will terminate the read operation if input does not arrive -after waiting for the timeout period, return failure and set the -`ERRNO' variable to an appropriate string value. A negative or zero -value for the timeout is the same as specifying no timeout at all. + `gawk' terminates the read operation if input does not arrive after +waiting for the timeout period, returns failure and sets the `ERRNO' +variable to an appropriate string value. A negative or zero value for +the timeout is the same as specifying no timeout at all. - A timeout can also be set for reading from the terminal in the + A timeout can also be set for reading from the keyboard in the implicit loop that reads input records and matches them against patterns, like so: @@ -5644,23 +5883,118 @@ writing. ---------- Footnotes ---------- - (1) This assumes that standard input is the keyboard + (1) This assumes that standard input is the keyboard. -File: gawk.info, Node: Command line directories, Prev: Read Timeout, Up: Reading Files +File: gawk.info, Node: Command-line directories, Next: Input Summary, Prev: Read Timeout, Up: Reading Files 4.11 Directories On The Command Line ==================================== According to the POSIX standard, files named on the `awk' command line -must be text files. It is a fatal error if they are not. Most -versions of `awk' treat a directory on the command line as a fatal -error. +must be text files; it is a fatal error if they are not. Most versions +of `awk' treat a directory on the command line as a fatal error. By default, `gawk' produces a warning for a directory on the command -line, but otherwise ignores it. If either of the `--posix' or -`--traditional' options is given, then `gawk' reverts to treating a -directory on the command line as a fatal error. +line, but otherwise ignores it. This makes it easier to use shell +wildcards with your `awk' program: + + $ gawk -f whizprog.awk * Directories could kill this progam + + If either of the `--posix' or `--traditional' options is given, then +`gawk' reverts to treating a directory on the command line as a fatal +error. + + *Note Extension Sample Readdir::, for a way to treat directories as +usable data from an `awk' program. + + +File: gawk.info, Node: Input Summary, Next: Input Exercises, Prev: Command-line directories, Up: Reading Files + +4.12 Summary +============ + + * Input is split into records based on the value of `RS'. The + possibilities are as follows: + + Value of `RS' Records are split on `awk' / `gawk' + ---------------------------------------------------------------------- + Any single That character `awk' + character + The empty string Runs of two or more `awk' + (`""') newlines + A regexp Text that matches the `gawk' + regexp + + * `gawk' sets `RT' to the text matched by `RS'. + + * After splitting the input into records, `awk' further splits the + record into individual fields, named `$1', `$2' and so on. `$0' is + the whole record, and `NF' indicates how many fields there are. + The default way to split fields is between whitespace characters. + + * Fields may be referenced using a variable, as in `$NF'. Fields + may also be assigned values, which causes the value of `$0' to be + recomputed when it is later referenced. Assigning to a field with + a number greater than `NF' creates the field and rebuilds the + record, using `OFS' to separate the fields. Incrementing `NF' + does the same thing. Decrementing `NF' throws away fields and + rebuilds the record. + + * Field splitting is more complicated than record splitting. + + Field separator value Fields are split ... `awk' / + `gawk' + ---------------------------------------------------------------------- + `FS == " "' On runs of whitespace `awk' + `FS == ANY SINGLE On that character `awk' + CHARACTER' + `FS == REGEXP' On text matching the `awk' + regexp + `FS == ""' Each individual character `gawk' + is a separate field + `FIELDWIDTHS == LIST OF Based on character `gawk' + COLUMNS' position + `FPAT == REGEXP' On text around text `gawk' + matching the regexp + + Using `FS = "\n"' causes the entire record to be a single field + (assuming that newlines separate records). + + * `FS' may be set from the command line using the `-F' option. This + can also be done using command-line variable assignment. + + * `PROCINFO["FS"]' can be used to see how fields are being split. + + * Use `getline' in its various forms to read additional records, + from the default input stream, from a file, or from a pipe or + co-process. + + * Use `PROCINFO[FILE, "READ_TIMEOUT"]' to cause reads to timeout for + FILE. + + * Directories on the command line are fatal for standard `awk'; + `gawk' ignores them if not in POSIX mode. + + + +File: gawk.info, Node: Input Exercises, Prev: Input Summary, Up: Reading Files + +4.13 Exercises +============== + + 1. Using the `FIELDWIDTHS' variable (*note Constant Size::), write a + program to read election data, where each record represents one + voter's votes. Come up with a way to define which columns are + associated with each ballot item, and print the total votes, + including abstentions, for each item. + + 2. *note Plain Getline::, presented a program to remove C-style + comments (`/* ... */') from the input. That program does not work + if one comment ends on one line and another one starts later on + the same line. That can be fixed by making one simple change. + What is it? + File: gawk.info, Node: Printing, Next: Expressions, Prev: Reading Files, Up: Top @@ -5696,6 +6030,8 @@ function. `gawk' allows access to inherited file descriptors. * Close Files And Pipes:: Closing Input and Output Files and Pipes. +* Output Summary:: Output summary. +* Output Exercises:: Exercises. File: gawk.info, Node: Print, Next: Print Examples, Up: Printing @@ -5704,9 +6040,9 @@ File: gawk.info, Node: Print, Next: Print Examples, Up: Printing ========================= The `print' statement is used for producing output with simple, -standardized formatting. Specify only the strings or numbers to print, -in a list separated by commas. They are output, separated by single -spaces, followed by a newline. The statement looks like this: +standardized formatting. You specify only the strings or numbers to +print, in a list separated by commas. They are output, separated by +single spaces, followed by a newline. The statement looks like this: print ITEM1, ITEM2, ... @@ -5727,6 +6063,10 @@ you forget to use the double-quote characters, your text is taken as an `awk' expression, and you will probably get an error. Keep in mind that a space is printed between any two items. + Note that the `print' statement is a statement and not an +expression--you can't use it the pattern part of a pattern-action +statement, for example. + File: gawk.info, Node: Print Examples, Next: Output Separators, Prev: Print, Up: Printing @@ -5773,8 +6113,8 @@ Here is the same program, without the comma: To someone unfamiliar with the `inventory-shipped' file, neither example's output makes much sense. A heading line at the beginning would make it clearer. Let's add some headings to our table of months -(`$1') and green crates shipped (`$2'). We do this using the `BEGIN' -pattern (*note BEGIN/END::) so that the headings are only printed once: +(`$1') and green crates shipped (`$2'). We do this using a `BEGIN' +rule (*note BEGIN/END::) so that the headings are only printed once: awk 'BEGIN { print "Month Crates" print "----- ------" } @@ -5981,17 +6321,19 @@ width. Here is a list of the format-control letters: valid wide character and then to print the multibyte encoding of that character. Similarly, when printing a numeric value, `gawk' allows the value to be within the numeric range of - values that can be held in a wide character. + values that can be held in a wide character. If the + conversion to multibyte encoding fails, `gawk' uses the low + eight bits of the value as the character to print. Other `awk' versions generally restrict themselves to printing the first byte of a string or to numeric values within the range of a single byte (0-255). -`%d, %i' +`%d', `%i' Print a decimal integer. The two control letters are equivalent. (The `%i' specification is for compatibility with ISO C.) -`%e, %E' +`%e', `%E' Print a number in scientific (exponential) notation; for example: printf "%4.3e\n", 1950 @@ -6013,7 +6355,8 @@ width. Here is a list of the format-control letters: On systems supporting IEEE 754 floating point format, values representing negative infinity are formatted as `-inf' or `-infinity', and positive infinity as `inf' and `infinity'. The - special "not a number" value formats as `-nan' or `nan'. + special "not a number" value formats as `-nan' or `nan' (*note + Math Definitions::). `%F' Like `%f' but the infinity and "not a number" values are spelled @@ -6022,7 +6365,7 @@ width. Here is a list of the format-control letters: The `%F' format is a POSIX extension to ISO C; not all systems support it. On those that don't, `gawk' uses `%f' instead. -`%g, %G' +`%g', `%G' Print a number in either scientific notation or in floating-point notation, whichever uses fewer characters; if the result is printed in scientific notation, `%G' uses `E' instead of `e'. @@ -6038,7 +6381,7 @@ width. Here is a list of the format-control letters: use, because all numbers in `awk' are floating-point; it is provided primarily for compatibility with C.) -`%x, %X' +`%x', `%X' Print an unsigned hexadecimal integer; `%X' uses the letters `A' through `F' instead of `a' through `f' (*note Nondecimal-numbers::). @@ -6213,11 +6556,12 @@ string, like so: This is not particularly easy to read but it does work. - C programmers may be used to supplying additional `l', `L', and `h' -modifiers in `printf' format strings. These are not valid in `awk'. -Most `awk' implementations silently ignore them. If `--lint' is -provided on the command line (*note Options::), `gawk' warns about -their use. If `--posix' is supplied, their use is a fatal error. + C programmers may be used to supplying additional modifiers (`h', +`j', `l', `L', `t', and `z') in `printf' format strings. These are not +valid in `awk'. Most `awk' implementations silently ignore them. If +`--lint' is provided on the command line (*note Options::), `gawk' +warns about their use. If `--posix' is supplied, their use is a fatal +error. File: gawk.info, Node: Printf Examples, Prev: Format Modifiers, Up: Printf @@ -6258,7 +6602,7 @@ they are last on their lines. They don't need to have spaces after them. The table could be made to look even nicer by adding headings to the -tops of the columns. This is done using the `BEGIN' pattern (*note +tops of the columns. This is done using a `BEGIN' rule (*note BEGIN/END::) so that the headers are only printed once, at the beginning of the `awk' program: @@ -6285,11 +6629,6 @@ be emphasized by storing it in a variable, like this: printf format, "----", "------" } { printf format, $1, $2 }' mail-list - At this point, it would be a worthwhile exercise to use the `printf' -statement to line up the headings and table data for the -`inventory-shipped' example that was covered earlier in the minor node -on the `print' statement (*note Print::). - File: gawk.info, Node: Redirection, Next: Special Files, Prev: Printf, Up: Printing @@ -6309,7 +6648,7 @@ commands, except that they are written inside the `awk' program. There are four forms of output redirection: output to a file, output appended to a file, output through a pipe to another command, and output -to a coprocess. They are all shown for the `print' statement, but they +to a coprocess. We show them all for the `print' statement, but they work identically for `printf': `print ITEMS > OUTPUT-FILE' @@ -6390,7 +6729,7 @@ work identically for `printf': FILE or COMMAND--it is not necessary to always use a string constant. Using a variable is generally a good idea, because (if you mean to refer to that same file or command) `awk' requires - that the string value be spelled identically every time. + that the string value be written identically every time. `print ITEMS |& COMMAND' This redirection prints the items to the input of COMMAND. The @@ -6486,9 +6825,9 @@ message to standard error in an `awk' program is as follows: This works by opening a pipeline to a shell command that can access the standard error stream that it inherits from the `awk' process. This is -far from elegant, and it is also inefficient, because it requires a -separate process. So people writing `awk' programs often don't do -this. Instead, they send the error messages to the screen, like this: +far from elegant, and it also requires a separate process. So people +writing `awk' programs often don't do this. Instead, they send the +error messages to the screen, like this: print "Serious error detected!" > "/dev/tty" @@ -6502,7 +6841,7 @@ run from a background job, it may not have a terminal at all. Then opening `/dev/tty' fails. `gawk' provides special file names for accessing the three standard -streams. (c.e.). It also provides syntax for accessing any other +streams. (c.e.) It also provides syntax for accessing any other inherited open files. If the file name matches one of these special names when `gawk' redirects input or output, then it directly uses the stream that the file name stands for. These special file names work @@ -6587,7 +6926,7 @@ names that `gawk' provides: behavior. -File: gawk.info, Node: Close Files And Pipes, Prev: Special Files, Up: Printing +File: gawk.info, Node: Close Files And Pipes, Next: Output Summary, Prev: Special Files, Up: Printing 5.8 Closing Input and Output Redirections ========================================= @@ -6695,14 +7034,15 @@ end-of-file return status from `getline'), the child process is not terminated;(1) more importantly, the file descriptor for the pipe is not closed and released until `close()' is called or `awk' exits. - `close()' will silently do nothing if given an argument that does -not represent a file, pipe or coprocess that was opened with a -redirection. + `close()' silently does nothing if given an argument that does not +represent a file, pipe or coprocess that was opened with a redirection. +In such a case, it returns a negative value, indicating an error. In +addition, `gawk' sets `ERRNO' to a string indicating the error. Note also that `close(FILENAME)' has no "magic" effects on the implicit loop that reads through the files named on the command line. -It is, more likely, a close of a file that was never opened, so `awk' -silently does nothing. +It is, more likely, a close of a file that was never opened with a +redirection, so `awk' silently does nothing. When using the `|&' operator to communicate with a coprocess, it is occasionally useful to be able to close one end of the two-way pipe @@ -6716,9 +7056,9 @@ I/O::, which discusses it in more detail and gives an example. Using `close()''s Return Value - In many versions of Unix `awk', the `close()' function is actually a -statement. It is a syntax error to try and use the return value from -`close()': (d.c.) + In many older versions of Unix `awk', the `close()' function is +actually a statement. It is a syntax error to try and use the return +value from `close()': (d.c.) command = "..." command | getline info @@ -6753,6 +7093,56 @@ call. See the system manual pages for information on how to decode this value. +File: gawk.info, Node: Output Summary, Next: Output Exercises, Prev: Close Files And Pipes, Up: Printing + +5.9 Summary +=========== + + * The `print' statement prints comma-separated expressions. Each + expression is separated by the value of `OFS' and terminated by + the value of `ORS'. `OFMT' provides the conversion format for + numeric values for the `print' statement. + + * The `printf' statement provides finer-grained control over output, + with format control letters for different data types and various + flags that modify the behavior of the format control letters. + + * Output from both `print' and `printf' may be redirected to files, + pipes, and co-processes. + + * `gawk' provides special file names for access to standard input, + output and error, and for network communications. + + * Use `close()' to close open file, pipe and co-process redirections. + For co-processes, it is possible to close only one direction of the + communications. + + + +File: gawk.info, Node: Output Exercises, Prev: Output Summary, Up: Printing + +5.10 Exercises +============== + + 1. Rewrite the program: + + awk 'BEGIN { print "Month Crates" + print "----- ------" } + { print $1, " ", $2 }' inventory-shipped + + from *note Output Separators::, by using a new value of `OFS'. + + 2. Use the `printf' statement to line up the headings and table data + for the `inventory-shipped' example that was covered in *note + Print::. + + 3. What happens if you forget the double quotes when redirecting + output, as follows: + + BEGIN { print "Serious error detected!" > /dev/stderr } + + + File: gawk.info, Node: Expressions, Next: Patterns and Actions, Prev: Printing, Up: Top 6 Expressions @@ -6778,6 +7168,7 @@ operators. * Function Calls:: A function call is an expression. * Precedence:: How various operators nest. * Locales:: How the locale affects things. +* Expressions Summary:: Expressions summary. File: gawk.info, Node: Values, Next: All Operators, Up: Expressions @@ -6847,7 +7238,8 @@ codes. (1) The internal representation of all numbers, including integers, uses double precision floating-point numbers. On most modern systems, -these are in IEEE 754 standard format. +these are in IEEE 754 standard format. *Note Arbitrary Precision +Arithmetic::, for much more information. File: gawk.info, Node: Nondecimal-numbers, Next: Regexp Constants, Prev: Scalar Constants, Up: Constants @@ -6932,8 +7324,9 @@ File: gawk.info, Node: Regexp Constants, Prev: Nondecimal-numbers, Up: Consta A regexp constant is a regular expression description enclosed in slashes, such as `/^beginning and end$/'. Most regexps used in `awk' programs are constant, but the `~' and `!~' matching operators can also -match computed or dynamic regexps (which are just ordinary strings or -variables that contain a regexp). +match computed or dynamic regexps (which are typically just ordinary +strings or variables that contain a regexp, but could be a more complex +expression). File: gawk.info, Node: Using Constant Regexps, Next: Variables, Prev: Constants, Up: Values @@ -6980,8 +7373,8 @@ the contents of the current input record. Constant regular expressions are also used as the first argument for the `gensub()', `sub()', and `gsub()' functions, as the second argument -of the `match()' function, and as the third argument of the -`patsplit()' function (*note String Functions::). Modern +of the `match()' function, and as the third argument of the `split()' +and `patsplit()' functions (*note String Functions::). Modern implementations of `awk', including `gawk', allow the third argument of `split()' to be a regexp constant, but some older implementations do not. (d.c.) This can lead to confusion when attempting to use regexp @@ -7005,12 +7398,12 @@ For example: } In this example, the programmer wants to pass a regexp constant to -the user-defined function `mysub', which in turn passes it on to either -`sub()' or `gsub()'. However, what really happens is that the `pat' -parameter is either one or zero, depending upon whether or not `$0' -matches `/hi/'. `gawk' issues a warning when it sees a regexp constant -used as a parameter to a user-defined function, since passing a truth -value in this way is probably not what was intended. +the user-defined function `mysub()', which in turn passes it on to +either `sub()' or `gsub()'. However, what really happens is that the +`pat' parameter is either one or zero, depending upon whether or not +`$0' matches `/hi/'. `gawk' issues a warning when it sees a regexp +constant used as a parameter to a user-defined function, since passing +a truth value in this way is probably not what was intended. File: gawk.info, Node: Variables, Next: Conversion, Prev: Using Constant Regexps, Up: Values @@ -7026,7 +7419,7 @@ on the `awk' command line. * Menu: * Using Variables:: Using variables in your programs. -* Assignment Options:: Setting variables on the command-line and a +* Assignment Options:: Setting variables on the command line and a summary of command-line syntax. This is an advanced method of input. @@ -7039,8 +7432,11 @@ File: gawk.info, Node: Using Variables, Next: Assignment Options, Up: Variabl Variables let you give names to values and refer to them later. Variables have already been used in many of the examples. The name of a variable must be a sequence of letters, digits, or underscores, and -it may not begin with a digit. Case is significant in variable names; -`a' and `A' are distinct variables. +it may not begin with a digit. Here, a "letter" is any one of the 52 +upper- and lowercase English letters. Other characters that may be +defined as letters in non-English locales are not valid in variable +names. Case is significant in variable names; `a' and `A' are distinct +variables. A variable name is a valid expression by itself; it represents the variable's current value. Variables are given new values with @@ -7119,6 +7515,22 @@ File: gawk.info, Node: Conversion, Prev: Variables, Up: Values 6.1.4 Conversion of Strings and Numbers --------------------------------------- +Number to string and string to number conversion are generally +straightforward. There can be subtleties to be aware of; this minor +node discusses this important facet of `awk'. + +* Menu: + +* Strings And Numbers:: How `awk' Converts Between Strings And + Numbers. +* Locale influences conversions:: How the locale may affect conversions. + + +File: gawk.info, Node: Strings And Numbers, Next: Locale influences conversions, Up: Conversion + +6.1.4.1 How `awk' Converts Between Strings And Numbers +...................................................... + Strings are converted to numbers and numbers are converted to strings, if the context of the `awk' program demands it. For example, if the value of either `foo' or `bar' in the expression `foo + bar' happens to @@ -7168,35 +7580,47 @@ value of `CONVFMT' may be. Given the following code fragment: `b' has the value `"12"', not `"12.00"'. (d.c.) + Pre-POSIX `awk' Used `OFMT' For String Conversion + Prior to the POSIX standard, `awk' used the value of `OFMT' for converting numbers to strings. `OFMT' specifies the output format to use when printing numbers with `print'. `CONVFMT' was introduced in order to separate the semantics of conversion from the semantics of printing. Both `CONVFMT' and `OFMT' have the same default value: `"%.6g"'. In the vast majority of cases, old `awk' programs do not -change their behavior. However, these semantics for `OFMT' are -something to keep in mind if you must port your new-style program to -older implementations of `awk'. We recommend that instead of changing -your programs, just port `gawk' itself. *Note Print::, for more -information on the `print' statement. - - And, once again, where you are can matter when it comes to converting -between numbers and strings. In *note Locales::, we mentioned that the -local character set and language (the locale) can affect how `gawk' -matches characters. The locale also affects numeric formats. In -particular, for `awk' programs, it affects the decimal point character. -The `"C"' locale, and most English-language locales, use the period -character (`.') as the decimal point. However, many (if not most) -European and non-English locales use the comma (`,') as the decimal -point character. +change their behavior. *Note Print::, for more information on the +`print' statement. + + ---------- Footnotes ---------- + + (1) Pathological cases can require up to 752 digits (!), but we +doubt that you need to worry about this. + + +File: gawk.info, Node: Locale influences conversions, Prev: Strings And Numbers, Up: Conversion + +6.1.4.2 Locales Can Influence Conversion +........................................ + +Where you are can matter when it comes to converting between numbers and +strings. The local character set and language--the "locale"--can +affect numeric formats. In particular, for `awk' programs, it affects +the decimal point character and the thousands-separator character. The +`"C"' locale, and most English-language locales, use the period +character (`.') as the decimal point and don't have a thousands +separator. However, many (if not most) European and non-English +locales use the comma (`,') as the decimal point character. European +locales often use either a space or a period as the thousands +separator, if they have one. The POSIX standard says that `awk' always uses the period as the decimal point when reading the `awk' program source code, and for command-line variable assignments (*note Other Arguments::). However, when interpreting input data, for `print' and `printf' output, and for number to string conversion, the local decimal point character is used. -(d.c.) Here are some examples indicating the difference in behavior, -on a GNU/Linux system: +(d.c.) In all cases, numbers in source code and in input data cannot +have a thousands separator. Here are some examples indicating the +difference in behavior, on a GNU/Linux system: $ export POSIXLY_CORRECT=1 Force POSIX behavior $ gawk 'BEGIN { printf "%g\n", 3.1415927 }' @@ -7241,11 +7665,6 @@ representation can have an unusual but important effect on the way `gawk' converts some special string values to numbers. The details are presented in *note POSIX Floating Point Problems::. - ---------- Footnotes ---------- - - (1) Pathological cases can require up to 752 digits (!), but we -doubt that you need to worry about this. - File: gawk.info, Node: All Operators, Next: Truth Values and Conditions, Prev: Values, Up: Expressions @@ -7401,9 +7820,9 @@ example: print (a " " (a = "panic")) } -It is not defined whether the assignment to `a' happens before or after -the value of `a' is retrieved for producing the concatenated value. -The result could be either `don't panic', or `panic panic'. +It is not defined whether the second assignment to `a' happens before +or after the value of `a' is retrieved for producing the concatenated +value. The result could be either `don't panic', or `panic panic'. The precedence of concatenation, when mixed with other operators, is often counter-intuitive. Consider this example: @@ -7427,13 +7846,14 @@ Otherwise, it's parsed as follows: => -12 (-24) => -12-24 - As mentioned earlier, when doing concatenation, _parenthesize_. -Otherwise, you're never quite sure what you'll get. + As mentioned earlier, when mixing concatenation with other +operators, _parenthesize_. Otherwise, you're never quite sure what +you'll get. ---------- Footnotes ---------- - (1) It happens that Brian Kernighan's `awk', `gawk' and `mawk' all -"get it right," but you should not rely on this. + (1) It happens that BWK `awk', `gawk' and `mawk' all "get it right," +but you should not rely on this. File: gawk.info, Node: Assignment Ops, Next: Increment Ops, Prev: Concatenation, Up: All Operators @@ -7476,9 +7896,9 @@ that the assignment stores in the specified variable, field, or array element. (Such values are called "rvalues".) It is important to note that variables do _not_ have permanent types. -A variable's type is simply the type of whatever value it happens to -hold at the moment. In the following program fragment, the variable -`foo' has a numeric value at first, and a string value later on: +A variable's type is simply the type of whatever value was last assigned +to it. In the following program fragment, the variable `foo' has a +numeric value at first, and a string value later on: foo = 1 print foo @@ -7551,9 +7971,10 @@ The indices of `bar' are practically guaranteed to be different, because the `rand()' function haven't been covered yet. *Note Arrays::, and see *note Numeric Functions::, for more information). This example illustrates an important fact about assignment operators: the lefthand -expression is only evaluated _once_. It is up to the implementation as -to which expression is evaluated first, the lefthand or the righthand. -Consider this example: +expression is only evaluated _once_. + + It is up to the implementation as to which expression is evaluated +first, the lefthand or the righthand. Consider this example: i = 1 a[i += 2] = i + 1 @@ -7566,14 +7987,14 @@ converted to a number. Operator Effect -------------------------------------------------------------------------- -LVALUE `+=' INCREMENT Adds INCREMENT to the value of LVALUE. -LVALUE `-=' DECREMENT Subtracts DECREMENT from the value of LVALUE. -LVALUE `*=' Multiplies the value of LVALUE by COEFFICIENT. +LVALUE `+=' INCREMENT Add INCREMENT to the value of LVALUE. +LVALUE `-=' DECREMENT Subtract DECREMENT from the value of LVALUE. +LVALUE `*=' Multiply the value of LVALUE by COEFFICIENT. COEFFICIENT -LVALUE `/=' DIVISOR Divides the value of LVALUE by DIVISOR. -LVALUE `%=' MODULUS Sets LVALUE to its remainder by MODULUS. +LVALUE `/=' DIVISOR Divide the value of LVALUE by DIVISOR. +LVALUE `%=' MODULUS Set LVALUE to its remainder by MODULUS. LVALUE `^=' POWER -LVALUE `**=' POWER Raises LVALUE to the power POWER. (c.e.) +LVALUE `**=' POWER Raise LVALUE to the power POWER. (c.e.) Table 6.2: Arithmetic Assignment Operators @@ -7596,8 +8017,8 @@ A workaround is: awk '/[=]=/' /dev/null - `gawk' does not have this problem, nor do the other freely available -versions described in *note Other Versions::. + `gawk' does not have this problem; BWK `awk' and `mawk' also do not +(*note Other Versions::). File: gawk.info, Node: Increment Ops, Prev: Assignment Ops, Up: All Operators @@ -7612,13 +8033,13 @@ they are convenient abbreviations for very common operations. The operator used for adding one is written `++'. It can be used to increment a variable either before or after taking its value. To -pre-increment a variable `v', write `++v'. This adds one to the value -of `v'--that new value is also the value of the expression. (The +"pre-increment" a variable `v', write `++v'. This adds one to the +value of `v'--that new value is also the value of the expression. (The assignment expression `v += 1' is completely equivalent.) Writing the -`++' after the variable specifies post-increment. This increments the -variable value just the same; the difference is that the value of the -increment expression itself is the variable's _old_ value. Thus, if -`foo' has the value four, then the expression `foo++' has the value +`++' after the variable specifies "post-increment". This increments +the variable value just the same; the difference is that the value of +the increment expression itself is the variable's _old_ value. Thus, +if `foo' has the value four, then the expression `foo++' has the value four, but it changes the value of `foo' to five. In other words, the operator returns the old value of the variable, but with the side effect of incrementing it. @@ -7761,14 +8182,11 @@ File: gawk.info, Node: Variable Typing, Next: Comparison Operators, Up: Typin 6.3.2.1 String Type Versus Numeric Type ....................................... -The 1992 POSIX standard introduced the concept of a "numeric string", -which is simply a string that looks like a number--for example, -`" +2"'. This concept is used for determining the type of a variable. -The type of the variable is important because the types of two variables -determine how they are compared. The various versions of the POSIX -standard did not get the rules quite right for several editions. -Fortunately, as of at least the 2008 standard (and possibly earlier), -the standard has been fixed, and variable typing follows these rules:(1) +The POSIX standard introduced the concept of a "numeric string", which +is simply a string that looks like a number--for example, `" +2"'. +This concept is used for determining the type of a variable. The type +of the variable is important because the types of two variables +determine how they are compared. Variable typing follows these rules: * A numeric constant or the result of a numeric operation has the NUMERIC attribute. @@ -7814,7 +8232,7 @@ operands, according to the following symmetric matrix: user input--should be treated as numeric, even though it is actually made of characters and is therefore also a string. Thus, for example, the string constant `" +3.14"', when it appears in program source code, -is a string--even though it looks numeric--and is _never_ treated as +is a string--even though it looks numeric--and is _never_ treated as a number for comparison purposes. In short, when one operand is a "pure" string, such as a string @@ -7825,10 +8243,9 @@ comparison is performed. characters, and so is first and foremost of STRING type; input strings that look numeric are additionally given the STRNUM attribute. Thus, the six-character input string ` +3.14' receives the STRNUM attribute. -In contrast, the eight-character literal `" +3.14"' appearing in -program text is a string constant. The following examples print `1' -when the comparison between the two different constants is true, `0' -otherwise: +In contrast, the eight characters `" +3.14"' appearing in program text +comprise a string constant. The following examples print `1' when the +comparison between the two different constants is true, `0' otherwise: $ echo ' +3.14' | gawk '{ print $0 == " +3.14" }' True -| 1 @@ -7847,11 +8264,6 @@ otherwise: $ echo ' +3.14' | gawk '{ print $1 == 3.14 }' True -| 1 - ---------- Footnotes ---------- - - (1) `gawk' has followed these rules for many years, and it is -gratifying that the POSIX standard is also now correct. - File: gawk.info, Node: Comparison Operators, Next: POSIX String Comparison, Prev: Variable Typing, Up: Typing and Comparison @@ -7950,7 +8362,7 @@ has the value one if `x' contains `foo', such as `"Oh, what a fool am I!"'. The righthand operand of the `~' and `!~' operators may be either a -regexp constant (`/.../') or an ordinary expression. In the latter +regexp constant (`/'...`/') or an ordinary expression. In the latter case, the value of the expression as a string is used as a dynamic regexp (*note Regexp Usage::; also *note Computed Regexps::). @@ -7971,9 +8383,10 @@ File: gawk.info, Node: POSIX String Comparison, Prev: Comparison Operators, U .......................................... The POSIX standard says that string comparison is performed based on -the locale's collating order. This is usually very different from the -results obtained when doing straight character-by-character -comparison.(1) +the locale's "collating order". This is the order in which characters +sort, as defined by the locale (for more discussion, *note Ranges and +Locales::). This order is usually very different from the results +obtained when doing straight character-by-character comparison.(1) Because this behavior differs considerably from existing practice, `gawk' only implements it when in POSIX mode (*note Options::). Here @@ -8053,9 +8466,9 @@ because of the way they work. Evaluation of the full expression is "short-circuited" if the result can be determined part way through its evaluation. - Statements that use `&&' or `||' can be continued simply by putting -a newline after them. But you cannot put a newline in front of either -of these operators without using backslash continuation (*note + Statements that end with `&&' or `||' can be continued simply by +putting a newline after them. But you cannot put a newline in front of +either of these operators without using backslash continuation (*note Statements/Lines::). The actual value of an expression using the `!' operator is either @@ -8066,7 +8479,7 @@ following program is one way to print lines in between special bracketing lines: $1 == "START" { interested = ! interested; next } - interested == 1 { print } + interested { print } $1 == "END" { interested = ! interested; next } The variable `interested', as with all `awk' variables, starts out @@ -8076,6 +8489,14 @@ using `!'. The next rule prints lines as long as `interested' is true. When a line is seen whose first field is `END', `interested' is toggled back to false.(1) + Most commonly, the `!' operator is used in the conditions of `if' +and `while' statements, where it often makes more sense to phrase the +logic in the negative: + + if (! SOME CONDITION || SOME OTHER CONDITION) { + ... DO WHATEVER PROCESSING ... + } + NOTE: The `next' statement is discussed in *note Next Statement::. `next' tells `awk' to skip the rest of the rules, get the next record, and start processing the rules over again at the top. The @@ -8125,7 +8546,7 @@ not. *Note Arrays::, for more information about arrays. continued simply by putting a newline after either character. However, putting a newline in front of either character does not work without using backslash continuation (*note Statements/Lines::). If `--posix' -is specified (*note Options::), then this extension is disabled. +is specified (*note Options::), this extension is disabled. File: gawk.info, Node: Function Calls, Next: Precedence, Prev: Truth Values and Conditions, Up: Expressions @@ -8142,6 +8563,8 @@ available in every `awk' program. The `sqrt()' function is one of these. *Note Built-in::, for a list of built-in functions and their descriptions. In addition, you can define functions for use in your program. *Note User-defined::, for instructions on how to do this. +Finally, `gawk' lets you write functions in C or C++ that may be called +from your program: see *note Dynamic Extensions::. The way to use a function is with a "function call" expression, which consists of the function name followed immediately by a list of @@ -8173,19 +8596,21 @@ the number of which to take the square root: If those arguments are not supplied, the functions use a reasonable default value. *Note Built-in::, for full details. If arguments are omitted in calls to user-defined functions, then those arguments are -treated as local variables and initialized to the empty string (*note -User-defined::). +treated as local variables. Such local variables act like the empty +string if referenced where a string value is required, and like zero if +referenced where a numeric value is required (*note User-defined::). As an advanced feature, `gawk' provides indirect function calls, which is a way to choose the function to call at runtime, instead of when you write the source code to your program. We defer discussion of this feature until later; see *note Indirect Calls::. - Like every other expression, the function call has a value, which is -computed by the function based on the arguments you give it. In this -example, the value of `sqrt(ARGUMENT)' is the square root of ARGUMENT. -The following program reads numbers, one number per line, and prints the -square root of each one: + Like every other expression, the function call has a value, often +called the "return value", which is computed by the function based on +the arguments you give it. In this example, the return value of +`sqrt(ARGUMENT)' is the square root of ARGUMENT. The following program +reads numbers, one number per line, and prints the square root of each +one: $ awk '{ print "The square root of", $1, "is", sqrt($1) }' 1 @@ -8258,7 +8683,7 @@ to avoid the problem the expression can be rewritten as `$($0++)--'. This table presents `awk''s operators, in order of highest to lowest precedence: -`(...)' +`('...`)' Grouping. `$' @@ -8279,7 +8704,7 @@ precedence: `+ -' Addition, subtraction. -`String Concatenation' +String Concatenation There is no special symbol for concatenation. The operands are simply written side by side (*note Concatenation::). @@ -8320,13 +8745,15 @@ precedence: POSIX. For maximum portability, do not use them. -File: gawk.info, Node: Locales, Prev: Precedence, Up: Expressions +File: gawk.info, Node: Locales, Next: Expressions Summary, Prev: Precedence, Up: Expressions 6.6 Where You Are Makes A Difference ==================================== Modern systems support the notion of "locales": a way to tell the -system about the local character set and language. +system about the local character set and language. The ISO C standard +defines a default `"C"' locale, which is an environment that is typical +of what many C programmers are used to. Once upon a time, the locale setting used to affect regexp matching (*note Ranges and Locales::), but this is no longer true. @@ -8338,6 +8765,13 @@ much better performance when reading records. Otherwise, `gawk' has to make several function calls, _per input character_, to find the record terminator. + Locales can affect how dates and times are formatted (*note Time +Functions::). For example, a common way to abbreviate the date +September 4, 2015 in the United States is "9/4/15." In many countries +in Europe, however, it is abbreviated "4.9.15." Thus, the `%x' +specification in a `"US"' locale might produce `9/4/15', while in a +`"EUROPE"' locale, it might produce `4.9.15'. + According to POSIX, string comparison is also affected by locales (similar to regular expressions). The details are presented in *note POSIX String Comparison::. @@ -8347,6 +8781,63 @@ used when `gawk' parses input data. This is discussed in detail in *note Conversion::. +File: gawk.info, Node: Expressions Summary, Prev: Locales, Up: Expressions + +6.7 Summary +=========== + + * Expressions are the basic elements of computation in programs. + They are built from constants, variables, function calls and + combinations of the various kinds of values with operators. + + * `awk' supplies three kinds of constants: numeric, string, and + regexp. `gawk' lets you specify numeric constants in octal and + hexadecimal (bases 8 and 16) in addition to decimal (base 10). In + certain contexts, a standalone regexp constant such as `/foo/' has + the same meaning as `$0 ~ /foo/'. + + * Variables hold values between uses in computations. A number of + built-in variables provide information to your `awk' program, and + a number of others let you control how `awk' behaves. + + * Numbers are automatically converted to strings, and strings to + numbers, as needed by `awk'. Numeric values are converted as if + they were formatted with `sprintf()' using the format in `CONVFMT'. + Locales can influence the conversions. + + * `awk' provides the usual arithmetic operators (addition, + subtraction, multiplication, division, modulus), and unary plus + and minus. It also provides comparison operators, boolean + operators, and regexp matching operators. String concatenation is + accomplished by placing two expressions next to each other; there + is no explicit operator. The three-operand `?:' operator provides + an "if-else" test within expressions. + + * Assignment operators provide convenient shorthands for common + arithmetic operations. + + * In `awk', a value is considered to be true if it is non-zero _or_ + non-null. Otherwise, the value is false. + + * A value's type is set upon each assignment and may change over its + lifetime. The type determines how it behaves in comparisons + (string or numeric). + + * Function calls return a value which may be used as part of a larger + expression. Expressions used to pass parameter values are fully + evaluated before the function is called. `awk' provides built-in + and user-defined functions; this is described later on in this + Info file. + + * Operator precedence specifies the order in which operations are + performed, unless explicitly overridden by parentheses. `awk''s + operator precedence is compatible with that of C. + + * Locales can affect the format of data as output by an `awk' + program, and occasionally the format for data read as input. + + + File: gawk.info, Node: Patterns and Actions, Next: Arrays, Prev: Expressions, Up: Top 7 Patterns, Actions, and Variables @@ -8370,6 +8861,7 @@ top of. Now it's time to start building something useful. * Statements:: Describes the various control statements in detail. * Built-in Variables:: Summarizes the built-in variables. +* Pattern Action Summary:: Patterns and Actions summary. File: gawk.info, Node: Pattern Overview, Next: Using Shell Variables, Up: Patterns and Actions @@ -8398,10 +8890,10 @@ summary of the types of `awk' patterns: A single expression. It matches when its value is nonzero (if a number) or non-null (if a string). (*Note Expression Patterns::.) -`PAT1, PAT2' +`BEGPAT, ENDPAT' A pair of patterns separated by a comma, specifying a range of records. The range includes both the initial record that matches - PAT1 and the final record that matches PAT2. (*Note Ranges::.) + BEGPAT and the final record that matches ENDPAT. (*Note Ranges::.) `BEGIN' `END' @@ -8411,7 +8903,7 @@ summary of the types of `awk' patterns: `BEGINFILE' `ENDFILE' Special patterns for you to supply startup or cleanup actions to be - done on a per file basis. (*Note BEGINFILE/ENDFILE::.) + done on a per-file basis. (*Note BEGINFILE/ENDFILE::.) `EMPTY' The empty pattern matches every input record. (*Note Empty::.) @@ -8460,7 +8952,7 @@ precisely `li': `li'.) Contrast this with the following regular expression match, which accepts any record with a first field that contains `li': - $ awk '$1 ~ /foo/ { print $2 }' mail-list + $ awk '$1 ~ /li/ { print $2 }' mail-list -| 555-5553 -| 555-6699 @@ -8531,7 +9023,7 @@ record. When a record matches BEGPAT, the range pattern is "turned on" and the range pattern matches this record as well. As long as the range pattern stays turned on, it automatically matches every input record read. The range pattern also matches ENDPAT against every input -record; when this succeeds, the range pattern is turned off again for +record; when this succeeds, the range pattern is "turned off" again for the following record. Then the range pattern goes back to checking BEGPAT against each record. @@ -8663,10 +9155,10 @@ File: gawk.info, Node: I/O And BEGIN/END, Prev: Using BEGIN/END, Up: BEGIN/EN 7.1.4.2 Input/Output from `BEGIN' and `END' Rules ................................................. -There are several (sometimes subtle) points to remember when doing I/O -from a `BEGIN' or `END' rule. The first has to do with the value of -`$0' in a `BEGIN' rule. Because `BEGIN' rules are executed before any -input is read, there simply is no input record, and therefore no +There are several (sometimes subtle) points to be aware of when doing +I/O from a `BEGIN' or `END' rule. The first has to do with the value +of `$0' in a `BEGIN' rule. Because `BEGIN' rules are executed before +any input is read, there simply is no input record, and therefore no fields, when executing `BEGIN' rules. References to `$0' and the fields yield a null string or zero, depending upon the context. One way to give `$0' a real value is to execute a `getline' command without a @@ -8681,8 +9173,7 @@ number of fields from the last input record. Most probably due to an oversight, the standard does not say that `$0' is also preserved, although logically one would think that it should be. In fact, `gawk' does preserve the value of `$0' for use in `END' rules. Be aware, -however, that Brian Kernighan's `awk', and possibly other -implementations, do not. +however, that BWK `awk', and possibly other implementations, do not. The third point follows from the first two. The meaning of `print' inside a `BEGIN' or `END' rule is the same as always: `print $0'. If @@ -8734,10 +9225,10 @@ tasks that would otherwise be difficult or impossible to perform: entirely. Otherwise, `gawk' exits with the usual fatal error. * If you have written extensions that modify the record handling (by - inserting an "input parser"), you can invoke them at this point, - before `gawk' has started processing the file. (This is a _very_ - advanced feature, currently used only by the `gawkextlib' project - (http://gawkextlib.sourceforge.net).) + inserting an "input parser," *note Input Parsers::), you can invoke + them at this point, before `gawk' has started processing the file. + (This is a _very_ advanced feature, currently used only by the + `gawkextlib' project (http://gawkextlib.sourceforge.net).) The `ENDFILE' rule is called when `gawk' has finished processing the last record in an input file. For the last input file, it will be @@ -8756,7 +9247,7 @@ either a `BEGINFILE' or and `ENDFILE' rule. The `nextfile' statement but not inside an `ENDFILE' rule. The `getline' statement (*note Getline::) is restricted inside both -`BEGINFILE' and `ENDFILE'. Only the `getline VARIABLE < FILE' form is +`BEGINFILE' and `ENDFILE': only redirected forms of `getline' are allowed. `BEGINFILE' and `ENDFILE' are `gawk' extensions. In most other @@ -8789,15 +9280,15 @@ to get the value of the shell variable into the body of the `awk' program. The most common method is to use shell quoting to substitute the -variable's value into the program inside the script. For example, in -the following program: +variable's value into the program inside the script. For example, +consider the following program: printf "Enter search pattern: " read pattern awk "/$pattern/ "'{ nmatches++ } END { print nmatches, "found" }' /path/to/data -the `awk' program consists of two pieces of quoted text that are +The `awk' program consists of two pieces of quoted text that are concatenated together to form the program. The first part is double-quoted, which allows substitution of the `pattern' shell variable inside the quotes. The second part is single-quoted. @@ -8809,7 +9300,7 @@ quotes when reading the program. A better method is to use `awk''s variable assignment feature (*note Assignment Options::) to assign the shell variable's value to an `awk' -variable's value. Then use dynamic regexps to match the pattern (*note +variable. Then use dynamic regexps to match the pattern (*note Computed Regexps::). The following shows how to redo the previous example using this technique: @@ -8840,19 +9331,19 @@ which (but not both) may be omitted. The purpose of the "action" is to tell `awk' what to do once a match for the pattern is found. Thus, in outline, an `awk' program generally looks like this: - [PATTERN] { ACTION } - PATTERN [{ ACTION }] + [PATTERN] `{ ACTION }' + PATTERN [`{ ACTION }'] ... - function NAME(ARGS) { ... } + `function NAME(ARGS) { ... }' ... An action consists of one or more `awk' "statements", enclosed in -curly braces (`{...}'). Each statement specifies one thing to do. The -statements are separated by newlines or semicolons. The curly braces -around an action must be used even if the action contains only one -statement, or if it contains no statements at all. However, if you -omit the action entirely, omit the curly braces as well. An omitted -action is equivalent to `{ print $0 }': +braces (`{...}'). Each statement specifies one thing to do. The +statements are separated by newlines or semicolons. The braces around +an action must be used even if the action contains only one statement, +or if it contains no statements at all. However, if you omit the +action entirely, omit the braces as well. An omitted action is +equivalent to `{ print $0 }': /foo/ { } match `foo', do nothing -- empty action /foo/ match `foo', print the record -- omitted action @@ -8871,9 +9362,9 @@ Control statements well as a few special ones (*note Statements::). Compound statements - Consist of one or more statements enclosed in curly braces. A - compound statement is used in order to put several statements - together in the body of an `if', `while', `do', or `for' statement. + Enclose one or more statements in braces. A compound statement is + used in order to put several statements together in the body of an + `if', `while', `do', or `for' statement. Input statements Use the `getline' command (*note Getline::). Also supplied in @@ -8902,7 +9393,7 @@ statements contain other statements. For example, the `if' statement contains another statement that may or may not be executed. The contained statement is called the "body". To include more than one statement in the body, group them into a single "compound statement" -with curly braces, separating them with newlines or semicolons. +with braces, separating them with newlines or semicolons. * Menu: @@ -8931,7 +9422,7 @@ File: gawk.info, Node: If Statement, Next: While Statement, Up: Statements The `if'-`else' statement is `awk''s decision-making statement. It looks like this: - if (CONDITION) THEN-BODY [else ELSE-BODY] + `if (CONDITION) THEN-BODY' [`else ELSE-BODY'] The CONDITION is an expression that controls what the rest of the statement does. If the CONDITION is true, THEN-BODY is executed; @@ -8950,8 +9441,8 @@ the value of `x' is evenly divisible by two), then the first `print' statement is executed; otherwise, the second `print' statement is executed. If the `else' keyword appears on the same line as THEN-BODY and THEN-BODY is not a compound statement (i.e., not surrounded by -curly braces), then a semicolon must separate THEN-BODY from the `else'. -To illustrate this, the previous example can be rewritten as: +braces), then a semicolon must separate THEN-BODY from the `else'. To +illustrate this, the previous example can be rewritten as: if (x % 2 == 0) print "x is even"; else print "x is odd" @@ -9136,7 +9627,8 @@ File: gawk.info, Node: Switch Statement, Next: Break Statement, Prev: For Sta 7.4.5 The `switch' Statement ---------------------------- -This minor node describes a `gawk'-specific feature. +This minor node describes a `gawk'-specific feature. If `gawk' is in +compatibility mode (*note Options::), it is not available. The `switch' statement allows the evaluation of an expression and the execution of statements based on a `case' match. Case statements @@ -9163,32 +9655,36 @@ match to a given case is made, the case statement bodies execute until a `break', `continue', `next', `nextfile' or `exit' is encountered, or the end of the `switch' statement itself. For example: - switch (NR * 2 + 1) { - case 3: - case "11": - print NR - 1 - break - - case /2[[:digit:]]+/: - print NR - - default: - print NR + 1 - - case -1: - print NR * -1 + while ((c = getopt(ARGC, ARGV, "aksx")) != -1) { + switch (c) { + case "a": + # report size of all files + all_files = TRUE; + break + case "k": + BLOCK_SIZE = 1024 # 1K block size + break + case "s": + # do sums only + sum_only = TRUE + break + case "x": + # don't cross filesystems + fts_flags = or(fts_flags, FTS_XDEV) + break + case "?": + default: + usage() + break + } } Note that if none of the statements specified above halt execution of a matched `case' statement, execution falls through to the next -`case' until execution halts. In the above example, for any case value -starting with `2' followed by one or more digits, the `print' statement -is executed and then falls through into the `default' section, -executing its `print' statement. In turn, the -1 case will also be -executed since the `default' does not halt execution. - - This `switch' statement is a `gawk' extension. If `gawk' is in -compatibility mode (*note Options::), it is not available. +`case' until execution halts. In the above example, the `case' for +`"?"' falls through to the `default' case, which is to call a function +named `usage()'. (The `getopt()' function being called here is +described in *note Getopt Function::.) File: gawk.info, Node: Break Statement, Next: Continue Statement, Prev: Switch Statement, Up: Statements @@ -9202,15 +9698,15 @@ divisor of any integer, and also identifies prime numbers: # find smallest divisor of num { - num = $1 - for (div = 2; div * div <= num; div++) { - if (num % div == 0) - break - } - if (num % div == 0) - printf "Smallest divisor of %d is %d\n", num, div - else - printf "%d is prime\n", num + num = $1 + for (div = 2; div * div <= num; div++) { + if (num % div == 0) + break + } + if (num % div == 0) + printf "Smallest divisor of %d is %d\n", num, div + else + printf "%d is prime\n", num } When the remainder is zero in the first `if' statement, `awk' @@ -9225,17 +9721,17 @@ Statement::.) # find smallest divisor of num { - num = $1 - for (div = 2; ; div++) { - if (num % div == 0) { - printf "Smallest divisor of %d is %d\n", num, div - break - } - if (div * div > num) { - printf "%d is prime\n", num - break + num = $1 + for (div = 2; ; div++) { + if (num % div == 0) { + printf "Smallest divisor of %d is %d\n", num, div + break + } + if (div * div > num) { + printf "%d is prime\n", num + break + } } - } } The `break' statement is also used to break out of the `switch' @@ -9245,8 +9741,8 @@ statement. This is discussed in *note Switch Statement::. loop or `switch'. However, although it was never documented, historical implementations of `awk' treated the `break' statement outside of a loop as if it were a `next' statement (*note Next -Statement::). (d.c.) Recent versions of Brian Kernighan's `awk' no -longer allow this usage, nor does `gawk'. +Statement::). (d.c.) Recent versions of BWK `awk' no longer allow +this usage, nor does `gawk'. File: gawk.info, Node: Continue Statement, Next: Next Statement, Prev: Break Statement, Up: Statements @@ -9289,15 +9785,16 @@ the previous example with the following `while' loop: print "" } -This program loops forever once `x' reaches 5. +This program loops forever once `x' reaches 5, since the increment +(`x++') is never reached. The `continue' statement has no special meaning with respect to the `switch' statement, nor does it have any meaning when used outside the body of a loop. Historical versions of `awk' treated a `continue' statement outside a loop the same way they treated a `break' statement outside a loop: as if it were a `next' statement (*note Next -Statement::). (d.c.) Recent versions of Brian Kernighan's `awk' no -longer work this way, nor does `gawk'. +Statement::). (d.c.) Recent versions of BWK `awk' no longer work this +way, nor does `gawk'. File: gawk.info, Node: Next Statement, Next: Nextfile Statement, Prev: Continue Statement, Up: Statements @@ -9328,9 +9825,8 @@ complicating the rest of the program, write a "weed out" rule near the beginning, in the following manner: NF != 4 { - err = sprintf("%s:%d: skipped: NF != 4\n", FILENAME, FNR) - print err > "/dev/stderr" - next + printf("%s:%d: skipped: NF != 4\n", FILENAME, FNR) > "/dev/stderr" + next } Because of the `next' statement, the program's subsequent rules won't @@ -9346,7 +9842,7 @@ rules. *Note BEGINFILE/ENDFILE::. According to the POSIX standard, the behavior is undefined if the `next' statement is used in a `BEGIN' or `END' rule. `gawk' treats it -as a syntax error. Although POSIX permits it, some other `awk' +as a syntax error. Although POSIX permits it, most other `awk' implementations don't allow the `next' statement inside function bodies (*note User-defined::). Just as with any other `next' statement, a `next' statement inside a function body reads the next record and @@ -9368,7 +9864,7 @@ reset to one, and processing starts over with the first rule in the program. If the `nextfile' statement causes the end of the input to be reached, then the code in any `END' rules is executed. An exception to this is when `nextfile' is invoked during execution of any statement in -an `END' rule; In this case, it causes the program to stop immediately. +an `END' rule; in this case, it causes the program to stop immediately. *Note BEGIN/END::. The `nextfile' statement is useful when there are many data files to @@ -9378,10 +9874,10 @@ would have to continue scanning the unwanted records. The `nextfile' statement accomplishes this much more efficiently. In `gawk', execution of `nextfile' causes additional things to -happen: any `ENDFILE' rules are executed except in the case as -mentioned below, `ARGIND' is incremented, and any `BEGINFILE' rules are -executed. (`ARGIND' hasn't been introduced yet. *Note Built-in -Variables::.) +happen: any `ENDFILE' rules are executed if `gawk' is not currently in +an `END' or `BEGINFILE' rule, `ARGIND' is incremented, and any +`BEGINFILE' rules are executed. (`ARGIND' hasn't been introduced yet. +*Note Built-in Variables::.) With `gawk', `nextfile' is useful inside a `BEGINFILE' rule to skip over a file that would otherwise cause `gawk' to exit with a fatal @@ -9399,12 +9895,12 @@ listed in `ARGV'. standard. See the Austin Group website (http://austingroupbugs.net/view.php?id=607). - The current version of the Brian Kernighan's `awk', and `mawk' -(*note Other Versions::) also support `nextfile'. However, they don't -allow the `nextfile' statement inside function bodies (*note -User-defined::). `gawk' does; a `nextfile' inside a function body -reads the next record and starts processing it with the first rule in -the program, just as any other `nextfile' statement. + The current version of BWK `awk', and `mawk' (*note Other +Versions::) also support `nextfile'. However, they don't allow the +`nextfile' statement inside function bodies (*note User-defined::). +`gawk' does; a `nextfile' inside a function body reads the next record +and starts processing it with the first rule in the program, just as +any other `nextfile' statement. File: gawk.info, Node: Exit Statement, Prev: Nextfile Statement, Up: Statements @@ -9416,7 +9912,7 @@ The `exit' statement causes `awk' to immediately stop executing the current rule and to stop processing input; any remaining input is ignored. The `exit' statement is written as follows: - exit [RETURN CODE] + `exit' [RETURN CODE] When an `exit' statement is executed from a `BEGIN' rule, the program stops processing everything immediately. No input records are @@ -9450,12 +9946,12 @@ with a nonzero status. An `awk' program can do this using an `exit' statement with a nonzero argument, as shown in the following example: BEGIN { - if (("date" | getline date_now) <= 0) { - print "Can't get system date" > "/dev/stderr" - exit 1 - } - print "current date is", date_now - close("date") + if (("date" | getline date_now) <= 0) { + print "Can't get system date" > "/dev/stderr" + exit 1 + } + print "current date is", date_now + close("date") } NOTE: For full portability, exit values should be between zero and @@ -9464,7 +9960,7 @@ statement with a nonzero argument, as shown in the following example: systems. -File: gawk.info, Node: Built-in Variables, Prev: Statements, Up: Patterns and Actions +File: gawk.info, Node: Built-in Variables, Next: Pattern Action Summary, Prev: Statements, Up: Patterns and Actions 7.5 Built-in Variables ====================== @@ -9477,9 +9973,9 @@ of these automatically, so that they enable you to tell `awk' how to do certain things. Others are set automatically by `awk', so that they carry information from the internal workings of `awk' to your program. - This minor node documents all the built-in variables of `gawk', most -of which are also documented in the chapters describing their areas of -activity. + This minor node documents all of `gawk''s built-in variables, most +of which are also documented in the major nodes describing their areas +of activity. * Menu: @@ -9496,8 +9992,13 @@ File: gawk.info, Node: User-modified, Next: Auto-set, Up: Built-in Variables ------------------------------------------- The following is an alphabetical list of variables that you can change -to control how `awk' does certain things. The variables that are -specific to `gawk' are marked with a pound sign (`#'). +to control how `awk' does certain things. + + The variables that are specific to `gawk' are marked with a pound +sign (`#'). These variables are `gawk' extensions. In other `awk' +implementations or if `gawk' is in compatibility mode (*note +Options::), they are not special. (Any exceptions are noted in the +description of each variable.) `BINMODE #' On non-POSIX systems, this variable specifies use of binary mode @@ -9510,14 +10011,11 @@ specific to `gawk' are marked with a pound sign (`#'). string value of `"rw"' or `"wr"' indicates that all files should use binary I/O. Any other string value is treated the same as `"rw"', but causes `gawk' to generate a warning message. - `BINMODE' is described in more detail in *note PC Using::. + `BINMODE' is described in more detail in *note PC Using::. `mawk' + *note Other Versions::), also supports this variable, but only + using numeric values. - This variable is a `gawk' extension. In other `awk' - implementations (except `mawk', *note Other Versions::), or if - `gawk' is in compatibility mode (*note Options::), it is not - special. - -`CONVFMT' +``CONVFMT'' This string controls conversion of numbers to strings (*note Conversion::). It works by being passed, in effect, as the first argument to the `sprintf()' function (*note String Functions::). @@ -9525,29 +10023,21 @@ specific to `gawk' are marked with a pound sign (`#'). POSIX standard. `FIELDWIDTHS #' - This is a space-separated list of columns that tells `gawk' how to - split input with fixed columnar boundaries. Assigning a value to + A space-separated list of columns that tells `gawk' how to split + input with fixed columnar boundaries. Assigning a value to `FIELDWIDTHS' overrides the use of `FS' and `FPAT' for field splitting. *Note Constant Size::, for more information. - If `gawk' is in compatibility mode (*note Options::), then - `FIELDWIDTHS' has no special meaning, and field-splitting - operations occur based exclusively on the value of `FS'. - `FPAT #' - This is a regular expression (as a string) that tells `gawk' to - create the fields based on text that matches the regular - expression. Assigning a value to `FPAT' overrides the use of `FS' - and `FIELDWIDTHS' for field splitting. *Note Splitting By - Content::, for more information. - - If `gawk' is in compatibility mode (*note Options::), then `FPAT' - has no special meaning, and field-splitting operations occur based - exclusively on the value of `FS'. + A regular expression (as a string) that tells `gawk' to create the + fields based on text that matches the regular expression. + Assigning a value to `FPAT' overrides the use of `FS' and + `FIELDWIDTHS' for field splitting. *Note Splitting By Content::, + for more information. `FS' - This is the input field separator (*note Field Separators::). The - value is a single-character string or a multicharacter regular + The input field separator (*note Field Separators::). The value + is a single-character string or a multicharacter regular expression that matches the separations between fields in an input record. If the value is the null string (`""'), then each character in the record becomes a separate field. (This behavior @@ -9583,13 +10073,9 @@ specific to `gawk' are marked with a pound sign (`#'). splitting when using a single-character field separator. *Note Case-sensitivity::. - If `gawk' is in compatibility mode (*note Options::), then - `IGNORECASE' has no special meaning. Thus, string and regexp - operations are always case-sensitive. - `LINT #' When this variable is true (nonzero or non-null), `gawk' behaves - as if the `--lint' command-line option is in effect. (*note + as if the `--lint' command-line option is in effect (*note Options::). With a value of `"fatal"', lint warnings become fatal errors. With a value of `"invalid"', only warnings about things that are actually invalid are issued. (This is not fully @@ -9605,13 +10091,13 @@ specific to `gawk' are marked with a pound sign (`#'). execution is independent of the flavor of `awk' being executed. `OFMT' - This string controls conversion of numbers to strings (*note - Conversion::) for printing with the `print' statement. It works - by being passed as the first argument to the `sprintf()' function - (*note String Functions::). Its default value is `"%.6g"'. - Earlier versions of `awk' also used `OFMT' to specify the format - for converting numbers to strings in general expressions; this is - now done by `CONVFMT'. + Controls conversion of numbers to strings (*note Conversion::) for + printing with the `print' statement. It works by being passed as + the first argument to the `sprintf()' function (*note String + Functions::). Its default value is `"%.6g"'. Earlier versions of + `awk' also used `OFMT' to specify the format for converting + numbers to strings in general expressions; this is now done by + `CONVFMT'. `OFS' This is the output field separator (*note Output Separators::). @@ -9619,49 +10105,45 @@ specific to `gawk' are marked with a pound sign (`#'). Its default value is `" "', a string consisting of a single space. `ORS' - This is the output record separator. It is output at the end of - every `print' statement. Its default value is `"\n"', the newline + The output record separator. It is output at the end of every + `print' statement. Its default value is `"\n"', the newline character. (*Note Output Separators::.) `PREC #' The working precision of arbitrary precision floating-point - numbers, 53 bits by default (*note Setting Precision::). + numbers, 53 bits by default (*note Setting precision::). `ROUNDMODE #' The rounding mode to use for arbitrary precision arithmetic on - numbers, by default `"N"' (`roundTiesToEven' in the IEEE-754 - standard) (*note Setting Rounding Mode::). + numbers, by default `"N"' (`roundTiesToEven' in the IEEE 754 + standard; *note Setting the rounding mode::). -`RS' - This is `awk''s input record separator. Its default value is a - string containing a single newline character, which means that an - input record consists of a single line of text. It can also be - the null string, in which case records are separated by runs of - blank lines. If it is a regexp, records are separated by matches - of the regexp in the input text. (*Note Records::.) +``RS'' + The input record separator. Its default value is a string + containing a single newline character, which means that an input + record consists of a single line of text. It can also be the null + string, in which case records are separated by runs of blank lines. + If it is a regexp, records are separated by matches of the regexp + in the input text. (*Note Records::.) The ability for `RS' to be a regular expression is a `gawk' extension. In most other `awk' implementations, or if `gawk' is in compatibility mode (*note Options::), just the first character of `RS''s value is used. -`SUBSEP' - This is the subscript separator. It has the default value of - `"\034"' and is used to separate the parts of the indices of a - multidimensional array. Thus, the expression `foo["A", "B"]' - really accesses `foo["A\034B"]' (*note Multidimensional::). +``SUBSEP'' + The subscript separator. It has the default value of `"\034"' and + is used to separate the parts of the indices of a multidimensional + array. Thus, the expression `foo["A", "B"]' really accesses + `foo["A\034B"]' (*note Multidimensional::). `TEXTDOMAIN #' - This variable is used for internationalization of programs at the - `awk' level. It sets the default text domain for specially marked - string constants in the source text, as well as for the - `dcgettext()', `dcngettext()' and `bindtextdomain()' functions - (*note Internationalization::). The default value of `TEXTDOMAIN' - is `"messages"'. - - This variable is a `gawk' extension. In other `awk' - implementations, or if `gawk' is in compatibility mode (*note - Options::), it is not special. + Used for internationalization of programs at the `awk' level. It + sets the default text domain for specially marked string constants + in the source text, as well as for the `dcgettext()', + `dcngettext()' and `bindtextdomain()' functions (*note + Internationalization::). The default value of `TEXTDOMAIN' is + `"messages"'. ---------- Footnotes ---------- @@ -9675,10 +10157,14 @@ File: gawk.info, Node: Auto-set, Next: ARGC and ARGV, Prev: User-modified, U The following is an alphabetical list of variables that `awk' sets automatically on certain occasions in order to provide information to -your program. The variables that are specific to `gawk' are marked -with a pound sign (`#'). +your program. + + The variables that are specific to `gawk' are marked with a pound +sign (`#'). These variables are `gawk' extensions. In other `awk' +implementations or if `gawk' is in compatibility mode (*note +Options::), they are not special. -`ARGC, ARGV' +`ARGC', `ARGV' The command-line arguments available to `awk' programs are stored in an array called `ARGV'. `ARGC' is the number of command-line arguments present. *Note Other Arguments::. Unlike most `awk' @@ -9723,10 +10209,6 @@ with a pound sign (`#'). program, `gawk' automatically sets it to a new value when the next file is opened. - This variable is a `gawk' extension. In other `awk' - implementations, or if `gawk' is in compatibility mode (*note - Options::), it is not special. - `ENVIRON' An associative array containing the values of the environment. The array indices are the environment variable names; the elements @@ -9746,12 +10228,12 @@ with a pound sign (`#'). Some operating systems may not have environment variables. On such systems, the `ENVIRON' array is empty (except for - `ENVIRON["AWKPATH"]', *note AWKPATH Variable:: and - `ENVIRON["AWKLIBPATH"]', *note AWKLIBPATH Variable::). + `ENVIRON["AWKPATH"]' and `ENVIRON["AWKLIBPATH"]'; *note AWKPATH + Variable::, and *note AWKLIBPATH Variable::). `ERRNO #' - If a system error occurs during a redirection for `getline', - during a read for `getline', or during a `close()' operation, then + If a system error occurs during a redirection for `getline', during + a read for `getline', or during a `close()' operation, then `ERRNO' contains a string describing the error. In addition, `gawk' clears `ERRNO' before opening each @@ -9765,19 +10247,14 @@ with a pound sign (`#'). `getline' returning -1. You are, of course, free to clear it yourself before doing an I/O operation. - This variable is a `gawk' extension. In other `awk' - implementations, or if `gawk' is in compatibility mode (*note - Options::), it is not special. - `FILENAME' - The name of the file that `awk' is currently reading. When no - data files are listed on the command line, `awk' reads from the - standard input and `FILENAME' is set to `"-"'. `FILENAME' is - changed each time a new file is read (*note Reading Files::). - Inside a `BEGIN' rule, the value of `FILENAME' is `""', since - there are no input files being processed yet.(1) (d.c.) Note, - though, that using `getline' (*note Getline::) inside a `BEGIN' - rule can give `FILENAME' a value. + The name of the current input file. When no data files are listed + on the command line, `awk' reads from the standard input and + `FILENAME' is set to `"-"'. `FILENAME' changes each time a new + file is read (*note Reading Files::). Inside a `BEGIN' rule, the + value of `FILENAME' is `""', since there are no input files being + processed yet.(1) (d.c.) Note, though, that using `getline' (*note + Getline::) inside a `BEGIN' rule can give `FILENAME' a value. `FNR' The current record number in the current file. `FNR' is @@ -9797,12 +10274,12 @@ with a pound sign (`#'). `FUNCTAB #' An array whose indices and corresponding values are the names of - all the user-defined or extension functions in the program. + all the built-in, user-defined and extension functions in the + program. NOTE: Attempting to use the `delete' statement with the - `FUNCTAB' array will cause a fatal error. Any attempt to - assign to an element of the `FUNCTAB' array will also cause a - fatal error. + `FUNCTAB' array causes a fatal error. Any attempt to assign + to an element of `FUNCTAB' also causes a fatal error. `NR' The number of input records `awk' has processed since the @@ -9828,15 +10305,21 @@ with a pound sign (`#'). `PROCINFO["identifiers"]' A subarray, indexed by the names of all identifiers used in - the text of the AWK program. For each identifier, the value - of the element is one of the following: + the text of the AWK program. An "identifier" is simply the + name of a variable (be it scalar or array), built-in + function, user-defined function, or extension function. For + each identifier, the value of the element is one of the + following: `"array"' The identifier is an array. + `"builtin"' + The identifier is a built-in function. + `"extension"' The identifier is an extension function loaded via - `@load'. + `@load' or `-l'. `"scalar"' The identifier is a scalar. @@ -9866,8 +10349,8 @@ with a pound sign (`#'). `PROCINFO["sorted_in"]' If this element exists in `PROCINFO', its value controls the - order in which array indices will be processed by `for (index - in array) ...' loops. Since this is an advanced feature, we + order in which array indices will be processed by `for (INDEX + in ARRAY)' loops. Since this is an advanced feature, we defer the full description until later; see *note Scanning an Array::. @@ -9884,8 +10367,8 @@ with a pound sign (`#'). The following additional elements in the array are available to provide information about the MPFR and GMP libraries if your - version of `gawk' supports arbitrary precision numbers (*note Gawk - and MPFR::): + version of `gawk' supports arbitrary precision numbers (*note + Arbitrary Precision Arithmetic::): `PROCINFO["mpfr_version"]' The version of the GNU MPFR library. @@ -9925,10 +10408,6 @@ with a pound sign (`#'). open input file, pipe, or coprocess. *Note Read Timeout::, for more information. - This array is a `gawk' extension. In other `awk' implementations, - or if `gawk' is in compatibility mode (*note Options::), it is not - special. - `RLENGTH' The length of the substring matched by the `match()' function (*note String Functions::). `RLENGTH' is set by invoking the @@ -9943,12 +10422,8 @@ with a pound sign (`#'). match was found. `RT #' - This is set each time a record is read. It contains the input text - that matched the text denoted by `RS', the record separator. - - This variable is a `gawk' extension. In other `awk' - implementations, or if `gawk' is in compatibility mode (*note - Options::), it is not special. + The input text that matched the text denoted by `RS', the record + separator. It is set every time a record is read. `SYMTAB #' An array whose indices are the names of all currently defined @@ -9984,7 +10459,7 @@ with a pound sign (`#'). return SYMTAB[variable] *= amount } - NOTE: In order to avoid severe time-travel paradoxes(2), + NOTE: In order to avoid severe time-travel paradoxes,(2) neither `FUNCTAB' nor `SYMTAB' are available as elements within the `SYMTAB' array. @@ -10081,8 +10556,16 @@ elements from `ARGV' (*note Delete::). All of these actions are typically done in the `BEGIN' rule, before actual processing of the input begins. *Note Split Program::, and see *note Tee Program::, for examples of each way of removing elements from -`ARGV'. The following fragment processes `ARGV' in order to examine, -and then remove, command-line options: +`ARGV'. + + To actually get options into an `awk' program, end the `awk' options +with `--' and then supply the `awk' program's options, in the following +manner: + + awk -f myprog.awk -- -v -q file1 file2 ... + + The following fragment processes `ARGV' in order to examine, and +then remove, the above command-line options: BEGIN { for (i = 1; i < ARGC; i++) { @@ -10100,25 +10583,69 @@ and then remove, command-line options: } } - To actually get the options into the `awk' program, end the `awk' -options with `--' and then supply the `awk' program's options, in the -following manner: - - awk -f myprog -- -v -q file1 file2 ... - - This is not necessary in `gawk'. Unless `--posix' has been -specified, `gawk' silently puts any unrecognized options into `ARGV' -for the `awk' program to deal with. As soon as it sees an unknown -option, `gawk' stops looking for other options that it might otherwise -recognize. The previous example with `gawk' would be: + Ending the `awk' options with `--' isn't necessary in `gawk'. Unless +`--posix' has been specified, `gawk' silently puts any unrecognized +options into `ARGV' for the `awk' program to deal with. As soon as it +sees an unknown option, `gawk' stops looking for other options that it +might otherwise recognize. The previous command line with `gawk' would +be: - gawk -f myprog -q -v file1 file2 ... + gawk -f myprog.awk -q -v file1 file2 ... Because `-q' is not a valid `gawk' option, it and the following `-v' are passed on to the `awk' program. (*Note Getopt Function::, for an `awk' library function that parses command-line options.) +File: gawk.info, Node: Pattern Action Summary, Prev: Built-in Variables, Up: Patterns and Actions + +7.6 Summary +=========== + + * Pattern-action pairs make up the basic elements of an `awk' + program. Patterns are either normal expressions, range + expressions, regexp constants, one of the special keywords + `BEGIN', `END', `BEGINFILE', `ENDFILE', or empty. The action + executes if the current record matches the pattern. Empty + (missing) patterns match all records. + + * I/O from `BEGIN' and `END' rules have certain constraints. This + is also true, only more so, for `BEGINFILE' and `ENDFILE' rules. + The latter two give you "hooks" into `gawk''s file processing, + allowing you to recover from a file that otherwise would cause a + fatal error (such as a file that cannot be opened). + + * Shell variables can be used in `awk' programs by careful use of + shell quoting. It is easier to pass a shell variable into `awk' + by using the `-v' option and an `awk' variable. + + * Actions consist of statements enclosed in curly braces. Statements + are built up from expressions, control statements, compound + statements, input and output statements, and deletion statements. + + * The control statements in `awk' are `if'-`else', `while', `for', + and `do'-`while'. `gawk' adds the `switch' statement. There are + two flavors of `for' statement: one for for performing general + looping, and the other iterating through an array. + + * `break' and `continue' let you exit early or start the next + iteration of a loop (or get out of a `switch'). + + * `next' and `nextfile' let you read the next record and start over + at the top of your program, or skip to the next input file and + start over, respectively. + + * The `exit' statement terminates your program. When executed from + an action (or function body) it transfers control to the `END' + statements. From an `END' statement body, it exits immediately. + You may pass an optional numeric value to be used at `awk''s exit + status. + + * Some built-in variables provide control over `awk', mainly for I/O. + Other variables convey information from `awk' to your program. + + + File: gawk.info, Node: Arrays, Next: Functions, Prev: Patterns and Actions, Up: Top 8 Arrays in `awk' @@ -10134,7 +10661,7 @@ remove array elements. It also describes how `awk' simulates multidimensional arrays, as well as some of the less obvious points about array usage. The major node moves on to discuss `gawk''s facility for sorting arrays, and ends with a brief description of `gawk''s -ability to support true multidimensional arrays. +ability to support true arrays of arrays. `awk' maintains a single set of names that may be used for naming variables, arrays, and functions (*note User-defined::). Thus, you @@ -10152,6 +10679,7 @@ cannot have a variable and an array with the same name in the same * Multidimensional:: Emulating multidimensional arrays in `awk'. * Arrays of Arrays:: True multidimensional arrays. +* Arrays Summary:: Summary of arrays. File: gawk.info, Node: Array Basics, Next: Delete, Up: Arrays @@ -10212,12 +10740,13 @@ declared.) A contiguous array of four elements might look like the following example, conceptually, if the element values are 8, `"foo"', `""', and -30: +30 as shown in *note figure-array-elements::: - +---------+---------+--------+---------+ - | 8 | "foo" | "" | 30 | Value - +---------+---------+--------+---------+ - 0 1 2 3 Index ++---------+---------+--------+---------+ +| 8 | "foo" | "" | 30 | @r{Value} ++---------+---------+--------+---------+ + 0 1 2 3 @r{Index} +Figure 8.1: A Contiguous Array Only the values are stored; the indices are implicit from the order of the values. Here, 8 is the value at index zero, because 8 appears in the @@ -10232,7 +10761,8 @@ array element value: Index 0 Value 8 Index 2 Value "" -The pairs are shown in jumbled order because their order is irrelevant. +The pairs are shown in jumbled order because their order is +irrelevant.(1) One advantage of associative arrays is that new pairs can be added at any time. For example, suppose a tenth element is added to the array @@ -10260,10 +10790,11 @@ from English to French: Here we decided to translate the number one in both spelled-out and numeric form--thus illustrating that a single array can have both -numbers and strings as indices. In fact, array subscripts are always -strings; this is discussed in more detail in *note Numeric Array -Subscripts::. Here, the number `1' isn't double-quoted, since `awk' -automatically converts it to a string. +numbers and strings as indices. (In fact, array subscripts are always +strings. There are some subtleties to how numbers work when used as +array subscripts; this is discussed in more detail in *note Numeric +Array Subscripts::.) Here, the number `1' isn't double-quoted, since +`awk' automatically converts it to a string. The value of `IGNORECASE' has no effect upon array subscripting. The identical string value used to store an array element must be used @@ -10274,6 +10805,11 @@ starting at one. (*Note String Functions::.) `awk''s arrays are efficient--the time to access an element is independent of the number of elements in the array. + ---------- Footnotes ---------- + + (1) The ordering will vary among `awk' implementations, which +typically use hash tables to store array elements and values. + File: gawk.info, Node: Reference to Elements, Next: Assigning Elements, Prev: Array Intro, Up: Array Basics @@ -10308,18 +10844,20 @@ been assigned any value as well as elements that have been deleted # Check if "foo" exists in a: Incorrect! if (a["foo"] != "") ... - This is incorrect, since this will _create_ `a["foo"]' if it - didn't exist before! + This is incorrect for two reasons. First, it _creates_ `a["foo"]' + if it didn't exist before! Second, it is valid (if a bit unusual) + to set an array element equal to the empty string. To determine whether an element exists in an array at a certain index, use the following expression: - IND in ARRAY + INDX in ARRAY -This expression tests whether the particular index IND exists, without +This expression tests whether the particular index INDX exists, without the side effect of creating that element if it is not present. The -expression has the value one (true) if `ARRAY[IND]' exists and zero -(false) if it does not exist. For example, this statement tests +expression has the value one (true) if `ARRAY[INDX]' exists and zero +(false) if it does not exist. (We use INDX here, since `index' is the +name of a built-in function.) For example, this statement tests whether the array `frequencies' contains the index `2': if (2 in frequencies) @@ -10453,19 +10991,54 @@ built-in function `length()'. The order in which elements of the array are accessed by this statement is determined by the internal arrangement of the array -elements within `awk' and normally cannot be controlled or changed. -This can lead to problems if new elements are added to ARRAY by -statements in the loop body; it is not predictable whether the `for' +elements within `awk' and in standard `awk' cannot be controlled or +changed. This can lead to problems if new elements are added to ARRAY +by statements in the loop body; it is not predictable whether the `for' loop will reach them. Similarly, changing VAR inside the loop may produce strange results. It is best to avoid such things. + As a point of information, `gawk' sets up the list of elements to be +iterated over before the loop starts, and does not change it. But not +all `awk' versions do so. Consider this program, named `loopcheck.awk': + + BEGIN { + a["here"] = "here" + a["is"] = "is" + a["a"] = "a" + a["loop"] = "loop" + for (i in a) { + j++ + a[j] = j + print i + } + } + + Here is what happens when run with `gawk': + + $ gawk -f loopcheck.awk + -| here + -| loop + -| a + -| is + + Contrast this to BWK `awk': + + $ nawk -f loopcheck.awk + -| loop + -| here + -| is + -| a + -| 1 + File: gawk.info, Node: Controlling Scanning, Prev: Scanning an Array, Up: Array Basics -8.1.6 Using Predefined Array Scanning Orders --------------------------------------------- +8.1.6 Using Predefined Array Scanning Orders With `gawk' +-------------------------------------------------------- + +This node describes a feature that is specific to `gawk'. -By default, when a `for' loop traverses an array, the order is + By default, when a `for' loop traverses an array, the order is undefined, meaning that the `awk' implementation determines the order in which the array is traversed. This order is usually based on the internal implementation of arrays and will vary from one version of @@ -10654,9 +11227,9 @@ at a time. `gawk' extension. As of September, 2012, it was accepted for inclusion into the POSIX standard. See the Austin Group website (http://austingroupbugs.net/view.php?id=544). This form of the - `delete' statement is also supported by Brian Kernighan's `awk' - and `mawk', as well as by a number of other implementations (*note - Other Versions::). + `delete' statement is also supported by BWK `awk' and `mawk', as + well as by a number of other implementations (*note Other + Versions::). The following statement provides a portable but nonobvious way to clear out an array:(1) @@ -10745,13 +11318,13 @@ might look like this: > line 2 > line 3' | awk '{ l[lines] = $0; ++lines } > END { - > for (i = lines-1; i >= 0; --i) + > for (i = lines - 1; i >= 0; i--) > print l[i] > }' -| line 3 -| line 2 - Unfortunately, the very first line of input data did not come out in + Unfortunately, the very first line of input data did not appear in the output! Upon first glance, we would think that this program should have @@ -10766,7 +11339,7 @@ following version of the program works correctly: { l[lines++] = $0 } END { - for (i = lines - 1; i >= 0; --i) + for (i = lines - 1; i >= 0; i--) print l[i] } @@ -10827,10 +11400,11 @@ multidimensional array, use the same operator (`in') that is used for single dimensional arrays. Write the whole sequence of indices in parentheses, separated by commas, as the left operand: - (SUBSCRIPT1, SUBSCRIPT2, ...) in ARRAY + if ((SUBSCRIPT1, SUBSCRIPT2, ...) in ARRAY) + ... - The following example treats its input as a two-dimensional array of -fields; it rotates this array 90 degrees clockwise and prints the + Here is an example that treats its input as a two-dimensional array +of fields; it rotates this array 90 degrees clockwise and prints the result. It assumes that all lines have the same number of elements: { @@ -10906,7 +11480,7 @@ The result is to set `separate[1]' to `"1"' and `separate[2]' to recovered. -File: gawk.info, Node: Arrays of Arrays, Prev: Multidimensional, Up: Arrays +File: gawk.info, Node: Arrays of Arrays, Next: Arrays Summary, Prev: Multidimensional, Up: Arrays 8.6 Arrays of Arrays ==================== @@ -11028,6 +11602,54 @@ by creating an arbitrary index: -| a +File: gawk.info, Node: Arrays Summary, Prev: Arrays of Arrays, Up: Arrays + +8.7 Summary +=========== + + * Standard `awk' provides one-dimensional associative arrays (arrays + indexed by string values). All arrays are associative; numeric + indices are converted automatically to strings. + + * Array elements are referenced as `ARRAY[INDX]'. Referencing an + element creates it if it did not exist previously. + + * The proper way to see if an array has an element with a given index + is to use the `in' operator: `INDX in ARRAY'. + + * Use `for (INDX in ARRAY) ...' to scan through all the individual + elements of an array. In the body of the loop, INDX takes on the + value of each element's index in turn. + + * The order in which a `for (INDX in ARRAY)' loop traverses an array + is undefined in POSIX `awk' and varies among implementations. + `gawk' lets you control the order by assigning special predefined + values to `PROCINFO["sorted_in"]'. + + * Use `delete ARRAY[INDX]' to delete an individual element. You may + also use `delete ARRAY' to delete all of the elements in the + array. This latter feature has been a common extension for many + years and is now standard, but may not be supported by all + commercial versions of `awk'. + + * Standard `awk' simulates multidimensional arrays by separating + subscript values with a comma. The values are concatenated into a + single string, separated by the value of `SUBSEP'. The fact that + such a subscript was created in this way is not retained; thus + changing `SUBSEP' may have unexpected consequences. You can use + `(SUB1, SUB2, ...) in ARRAY' to see if such a multidimensional + subscript exists in ARRAY. + + * `gawk' provides true arrays of arrays. You use a separate set of + square brackets for each dimension in such an array: + `data[row][col]', for example. Array elements may thus be either + scalar values (number or string) or another array. + + * Use the `isarray()' built-in function to determine if an array + element is itself a subarray. + + + File: gawk.info, Node: Functions, Next: Library Functions, Prev: Arrays, Up: Top 9 Functions @@ -11047,6 +11669,7 @@ major node describes these "user-defined" functions. * Built-in:: Summarizes the built-in functions. * User-defined:: Describes User-defined functions in detail. * Indirect Calls:: Choosing the function to call at runtime. +* Functions Summary:: Summary of functions. File: gawk.info, Node: Built-in, Next: User-defined, Up: Functions @@ -11134,6 +11757,21 @@ brackets ([ ]): `cos(X)' Return the cosine of X, with X in radians. +`div(NUMERATOR, DENOMINATOR, RESULT)' + Perform integer division, similar to the standard C function of the + same name. First, truncate `numerator' and `denominator' towards + zero, creating integer values. Clear the `result' array, and then + set `result["quotient"]' to the result of `numerator / + denominator', truncated towards zero to an integer, and set + `result["remainder"]' to the result of `numerator % denominator', + truncated towards zero to an integer. This function is primarily + intended for use with arbitrary length integers; it avoids + creating MPFR arbitrary precision floating-point values (*note + Arbitrary Precision Integers::). + + This function is a `gawk' extension. It is not available in + compatibility mode (*note Options::). + `exp(X)' Return the exponential of X (`e ^ X') or report an error if X is out of range. The range of values X can have depends on your @@ -11148,7 +11786,8 @@ brackets ([ ]): `log(X)' Return the natural logarithm of X, if X is positive; otherwise, - report an error. + return `NaN' ("not a number") on IEEE 754 systems. Additionally, + `gawk' prints a warning message when `x' is negative. `rand()' Return a random number. The values of `rand()' are uniformly @@ -11198,7 +11837,7 @@ brackets ([ ]): Return the positive square root of X. `gawk' prints a warning message if X is negative. Thus, `sqrt(4)' is 2. -`srand([X])' +`srand('[X]`)' Set the starting point, or seed, for generating random numbers to the value X. @@ -11219,6 +11858,9 @@ brackets ([ ]): easy to keep track of the seeds in case you need to consistently reproduce sequences of random numbers. + POSIX does not specify the initial seed; it differs among `awk' + implementations. + ---------- Footnotes ---------- (1) The C version of `rand()' on many Unix systems is known to @@ -11252,12 +11894,22 @@ returns the number of characters in a string, and not the number of bytes used to represent those characters. Similarly, `index()' works with character indices, and not byte indices. + CAUTION: A number of functions deal with indices into strings. + For these functions, the first character of a string is at + position (index) one. This is different from C and the languages + descended from it, where the first character is at position zero. + You need to remember this when doing index calculations, + particularly if you are used to C. + In the following list, optional parameters are enclosed in square brackets ([ ]). Several functions perform string substitution; the full discussion is provided in the description of the `sub()' function, which comes towards the end since the list is presented in alphabetic -order. Those functions that are specific to `gawk' are marked with a -pound sign (`#'): +order. + + Those functions that are specific to `gawk' are marked with a pound +sign (`#'). They are not available in compatibility mode (*note +Options::): * Menu: @@ -11265,8 +11917,8 @@ pound sign (`#'): `&' with `sub()', `gsub()', and `gensub()'. -`asort(SOURCE [, DEST [, HOW ] ]) #' -`asorti(SOURCE [, DEST [, HOW ] ]) #' +`asort('SOURCE [`,' DEST [`,' HOW ] ]`) #' +`asorti('SOURCE [`,' DEST [`,' HOW ] ]`) #' These two functions are similar in behavior, so they are described together. @@ -11313,10 +11965,7 @@ pound sign (`#'): a[2] = "last" a[3] = "middle" - `asort()' and `asorti()' are `gawk' extensions; they are not - available in compatibility mode (*note Options::). - -`gensub(REGEXP, REPLACEMENT, HOW [, TARGET]) #' +`gensub(REGEXP, REPLACEMENT, HOW' [`, TARGET']`) #' Search the target string TARGET for matches of the regular expression REGEXP. If HOW is a string beginning with `g' or `G' (short for "global"), then replace all matches of REGEXP with @@ -11366,10 +12015,7 @@ pound sign (`#'): If REGEXP does not match TARGET, `gensub()''s return value is the original unchanged value of TARGET. - `gensub()' is a `gawk' extension; it is not available in - compatibility mode (*note Options::). - -`gsub(REGEXP, REPLACEMENT [, TARGET])' +`gsub(REGEXP, REPLACEMENT' [`, TARGET']`)' Search TARGET for _all_ of the longest, leftmost, _nonoverlapping_ matching substrings it can find and replace them with REPLACEMENT. The `g' in `gsub()' stands for "global," which means replace @@ -11393,12 +12039,11 @@ pound sign (`#'): $ awk 'BEGIN { print index("peanut", "an") }' -| 3 - If FIND is not found, `index()' returns zero. (Remember that - string indices in `awk' start at one.) + If FIND is not found, `index()' returns zero. It is a fatal error to use a regexp constant for FIND. -`length([STRING])' +`length('[STRING]`)' Return the number of characters in STRING. If STRING is a number, the length of the digit string representing that number is returned. For example, `length("abcde")' is five. By contrast, @@ -11438,14 +12083,14 @@ pound sign (`#'): array argument is not portable. If `--posix' is supplied, using an array argument is a fatal error (*note Arrays::). -`match(STRING, REGEXP [, ARRAY])' +`match(STRING, REGEXP' [`, ARRAY']`)' Search STRING for the longest, leftmost substring matched by the - regular expression, REGEXP and return the character position, or - "index", at which that substring begins (one, if it starts at the + regular expression, REGEXP and return the character position + (index) at which that substring begins (one, if it starts at the beginning of STRING). If no match is found, return zero. - The REGEXP argument may be either a regexp constant (`/.../') or a - string constant (`"..."'). In the latter case, the string is + The REGEXP argument may be either a regexp constant (`/'...`/') or + a string constant (`"'...`"'). In the latter case, the string is treated as a regexp to be matched. *Note Computed Regexps::, for a discussion of the difference between the two forms, and the implications for writing your program correctly. @@ -11525,7 +12170,7 @@ pound sign (`#'): compatibility mode (*note Options::), using a third argument is a fatal error. -`patsplit(STRING, ARRAY [, FIELDPAT [, SEPS ] ]) #' +`patsplit(STRING, ARRAY' [`, FIELDPAT' [`, SEPS' ] ]`) #' Divide STRING into pieces defined by FIELDPAT and store the pieces in ARRAY and the separator strings in the SEPS array. The first piece is stored in `ARRAY[1]', the second piece in `ARRAY[2]', and @@ -11544,10 +12189,7 @@ pound sign (`#'): Before splitting the string, `patsplit()' deletes any previously existing elements in the arrays ARRAY and SEPS. - The `patsplit()' function is a `gawk' extension. In compatibility - mode (*note Options::), it is not available. - -`split(STRING, ARRAY [, FIELDSEP [, SEPS ] ])' +`split(STRING, ARRAY' [`, FIELDSEP' [`, SEPS' ] ]`)' Divide STRING into pieces separated by FIELDSEP and store the pieces in ARRAY and the separator strings in the SEPS array. The first piece is stored in `ARRAY[1]', the second piece in @@ -11612,6 +12254,9 @@ pound sign (`#'): has one element only. The value of that element is the original STRING. + In POSIX mode (*note Options::), the fourth argument is not + allowed. + `sprintf(FORMAT, EXPRESSION1, ...)' Return (without printing) the string that `printf' would have printed out with the same arguments (*note Printf::). For example: @@ -11637,18 +12282,15 @@ pound sign (`#'): Note also that `strtonum()' uses the current locale's decimal point for recognizing numbers (*note Locales::). - `strtonum()' is a `gawk' extension; it is not available in - compatibility mode (*note Options::). - -`sub(REGEXP, REPLACEMENT [, TARGET])' +`sub(REGEXP, REPLACEMENT' [`, TARGET']`)' Search TARGET, which is treated as a string, for the leftmost, longest substring matched by the regular expression REGEXP. Modify the entire string by replacing the matched text with REPLACEMENT. The modified string becomes the new value of TARGET. Return the number of substitutions made (zero or one). - The REGEXP argument may be either a regexp constant (`/.../') or a - string constant (`"..."'). In the latter case, the string is + The REGEXP argument may be either a regexp constant (`/'...`/') or + a string constant (`"'...`"'). In the latter case, the string is treated as a regexp to be matched. *Note Computed Regexps::, for a discussion of the difference between the two forms, and the implications for writing your program correctly. @@ -11713,7 +12355,7 @@ pound sign (`#'): into a string, and then the value of that string is treated as the regexp to match. -`substr(STRING, START [, LENGTH])' +`substr(STRING, START' [`, LENGTH' ]`)' Return a LENGTH-character-long substring of STRING, starting at character number START. The first character of a string is character number one.(3) For example, `substr("washington", 5, 3)' @@ -11726,11 +12368,11 @@ pound sign (`#'): remaining in the string, counting from character START. If START is less than one, `substr()' treats it as if it was one. - (POSIX doesn't specify what to do in this case: Brian Kernighan's - `awk' acts this way, and therefore `gawk' does too.) If START is - greater than the number of characters in the string, `substr()' - returns the null string. Similarly, if LENGTH is present but less - than or equal to zero, the null string is returned. + (POSIX doesn't specify what to do in this case: BWK `awk' acts + this way, and therefore `gawk' does too.) If START is greater + than the number of characters in the string, `substr()' returns + the null string. Similarly, if LENGTH is present but less than or + equal to zero, the null string is returned. The string returned by `substr()' _cannot_ be assigned. Thus, it is a mistake to attempt to change a portion of a string, as shown @@ -11786,23 +12428,27 @@ File: gawk.info, Node: Gory Details, Up: String Functions 9.1.3.1 More About `\' and `&' with `sub()', `gsub()', and `gensub()' ..................................................................... -When using `sub()', `gsub()', or `gensub()', and trying to get literal -backslashes and ampersands into the replacement text, you need to -remember that there are several levels of "escape processing" going on. + CAUTION: This section has been known to cause headaches. You + might want to skip it upon first reading. + + When using `sub()', `gsub()', or `gensub()', and trying to get +literal backslashes and ampersands into the replacement text, you need +to remember that there are several levels of "escape processing" going +on. First, there is the "lexical" level, which is when `awk' reads your -program and builds an internal copy of it that can be executed. Then -there is the runtime level, which is when `awk' actually scans the -replacement string to determine what to generate. +program and builds an internal copy of it to execute. Then there is +the runtime level, which is when `awk' actually scans the replacement +string to determine what to generate. At both levels, `awk' looks for a defined set of characters that can come after a backslash. At the lexical level, it looks for the escape sequences listed in *note Escape Sequences::. Thus, for every `\' that `awk' processes at the runtime level, you must type two backslashes at the lexical level. When a character that is not valid for an escape -sequence follows the `\', Brian Kernighan's `awk' and `gawk' both -simply remove the initial `\' and put the next character into the -string. Thus, for example, `"a\qb"' is treated as `"aqb"'. +sequence follows the `\', BWK `awk' and `gawk' both simply remove the +initial `\' and put the next character into the string. Thus, for +example, `"a\qb"' is treated as `"aqb"'. At the runtime level, the various functions handle sequences of `\' and `&' differently. The situation is (sadly) somewhat complex. @@ -11814,13 +12460,13 @@ is illustrated in *note table-sub-escapes::. You type `sub()' sees `sub()' generates ------- --------- -------------- - `\&' `&' the matched text - `\\&' `\&' a literal `&' - `\\\&' `\&' a literal `&' - `\\\\&' `\\&' a literal `\&' - `\\\\\&' `\\&' a literal `\&' - `\\\\\\&' `\\\&' a literal `\\&' - `\\q' `\q' a literal `\q' + `\&' `&' The matched text + `\\&' `\&' A literal `&' + `\\\&' `\&' A literal `&' + `\\\\&' `\\&' A literal `\&' + `\\\\\&' `\\&' A literal `\&' + `\\\\\\&' `\\\&' A literal `\\&' + `\\q' `\q' A literal `\q' Table 9.1: Historical Escape Sequence Processing for `sub()' and `gsub()' @@ -11834,50 +12480,25 @@ backslashes entered at the lexical level.) The problem with the historical approach is that there is no way to get a literal `\' followed by the matched text. - The 1992 POSIX standard attempted to fix this problem. That standard -says that `sub()' and `gsub()' look for either a `\' or an `&' after -the `\'. If either one follows a `\', that character is output -literally. The interpretation of `\' and `&' then becomes as shown in -*note table-sub-posix-92::. - - You type `sub()' sees `sub()' generates - ------- --------- -------------- - `&' `&' the matched text - `\\&' `\&' a literal `&' - `\\\\&' `\\&' a literal `\', then the matched text - `\\\\\\&' `\\\&' a literal `\&' - -Table 9.2: 1992 POSIX Rules for `sub()' and `gsub()' Escape Sequence -Processing + Several editions of the POSIX standard attempted to fix this problem +but weren't successful. The details are irrelevant at this point in +time. -This appears to solve the problem. Unfortunately, the phrasing of the -standard is unusual. It says, in effect, that `\' turns off the special -meaning of any following character, but for anything other than `\' and -`&', such special meaning is undefined. This wording leads to two -problems: - - * Backslashes must now be doubled in the REPLACEMENT string, breaking - historical `awk' programs. - - * To make sure that an `awk' program is portable, _every_ character - in the REPLACEMENT string must be preceded with a backslash.(1) - - Because of the problems just listed, in 1996, the `gawk' maintainer -submitted proposed text for a revised standard that reverts to rules -that correspond more closely to the original existing practice. The -proposed rules have special cases that make it possible to produce a -`\' preceding the matched text. This is shown in *note -table-sub-proposed::. + At one point, the `gawk' maintainer submitted proposed text for a +revised standard that reverts to rules that correspond more closely to +the original existing practice. The proposed rules have special cases +that make it possible to produce a `\' preceding the matched text. +This is shown in *note table-sub-proposed::. You type `sub()' sees `sub()' generates ------- --------- -------------- - `\\\\\\&' `\\\&' a literal `\&' - `\\\\&' `\\&' a literal `\', followed by the matched text - `\\&' `\&' a literal `&' - `\\q' `\q' a literal `\q' + `\\\\\\&' `\\\&' A literal `\&' + `\\\\&' `\\&' A literal `\', followed by the matched text + `\\&' `\&' A literal `&' + `\\q' `\q' A literal `\q' `\\\\' `\\' `\\' -Table 9.3: Proposed Rules For `sub()' And Backslash +Table 9.2: GNU `awk' Rules For `sub()' And Backslash In a nutshell, at the runtime level, there are now three special sequences of characters (`\\\&', `\\&' and `\&') whereas historically @@ -11885,11 +12506,11 @@ there was only one. However, as in the historical case, any `\' that is not part of one of these three sequences is not special and appears in the output literally. - `gawk' 3.0 and 3.1 follow these proposed POSIX rules for `sub()' and -`gsub()'. The POSIX standard took much longer to be revised than was -expected in 1996. The 2001 standard does not follow the above rules. -Instead, the rules there are somewhat simpler. The results are similar -except for one case. + `gawk' 3.0 and 3.1 follow these rules for `sub()' and `gsub()'. The +POSIX standard took much longer to be revised than was expected. In +addition, the `gawk' maintainer's proposal was lost during the +standardization process. The final rules are somewhat simpler. The +results are similar except for one case. The POSIX rules state that `\&' in the replacement string produces a literal `&', `\\' produces a literal `\', and `\' followed by anything @@ -11898,25 +12519,25 @@ rules are presented in *note table-posix-sub::. You type `sub()' sees `sub()' generates ------- --------- -------------- - `\\\\\\&' `\\\&' a literal `\&' - `\\\\&' `\\&' a literal `\', followed by the matched text - `\\&' `\&' a literal `&' - `\\q' `\q' a literal `\q' + `\\\\\\&' `\\\&' A literal `\&' + `\\\\&' `\\&' A literal `\', followed by the matched text + `\\&' `\&' A literal `&' + `\\q' `\q' A literal `\q' `\\\\' `\\' `\' -Table 9.4: POSIX Rules For `sub()' And `gsub()' +Table 9.3: POSIX Rules For `sub()' And `gsub()' The only case where the difference is noticeable is the last one: `\\\\' is seen as `\\' and produces `\' instead of `\\'. Starting with version 3.1.4, `gawk' followed the POSIX rules when `--posix' is specified (*note Options::). Otherwise, it continued to -follow the 1996 proposed rules, since that had been its behavior for -many years. +follow the proposed rules, since that had been its behavior for many +years. When version 4.0.0 was released, the `gawk' maintainer made the POSIX rules the default, breaking well over a decade's worth of -backwards compatibility.(2) Needless to say, this was a bad idea, and +backwards compatibility.(1) Needless to say, this was a bad idea, and as of version 4.0.1, `gawk' resumed its historical behavior, and only follows the POSIX rules when `--posix' is given. @@ -11929,14 +12550,14 @@ the `\' does not, as shown in *note table-gensub-escapes::. You type `gensub()' sees `gensub()' generates ------- ------------ ----------------- - `&' `&' the matched text - `\\&' `\&' a literal `&' - `\\\\' `\\' a literal `\' - `\\\\&' `\\&' a literal `\', then the matched text - `\\\\\\&' `\\\&' a literal `\&' - `\\q' `\q' a literal `q' + `&' `&' The matched text + `\\&' `\&' A literal `&' + `\\\\' `\\' A literal `\' + `\\\\&' `\\&' A literal `\', then the matched text + `\\\\\\&' `\\\&' A literal `\&' + `\\q' `\q' A literal `q' -Table 9.5: Escape Sequence Processing For `gensub()' +Table 9.4: Escape Sequence Processing For `gensub()' Because of the complexity of the lexical and runtime level processing and the special cases for `sub()' and `gsub()', we recommend the use of @@ -11955,9 +12576,7 @@ Although this makes a certain amount of sense, it can be surprising. ---------- Footnotes ---------- - (1) This consequence was certainly unintended. - - (2) This was rather naive of him, despite there being a note in this + (1) This was rather naive of him, despite there being a note in this section indicating that the next major version would move to the POSIX rules. @@ -11970,7 +12589,7 @@ File: gawk.info, Node: I/O Functions, Next: Time Functions, Prev: String Func The following functions relate to input/output (I/O). Optional parameters are enclosed in square brackets ([ ]): -`close(FILENAME [, HOW])' +`close('FILENAME [`,' HOW]`)' Close the file FILENAME for input or output. Alternatively, the argument may be a shell command that was used for creating a coprocess, or for redirecting to or from a pipe; then the @@ -11985,7 +12604,10 @@ parameters are enclosed in square brackets ([ ]): not matter. *Note Two-way I/O::, which discusses this feature in more detail and gives an example. -`fflush([FILENAME])' + Note that the second argument to `close()' is a `gawk' extension; + it is not available in compatibility mode (*note Options::). + +`fflush('[FILENAME]`)' Flush any buffered output associated with FILENAME, which is either a file opened for writing or a shell command for redirecting output to a pipe or coprocess. @@ -12001,10 +12623,10 @@ parameters are enclosed in square brackets ([ ]): function--`gawk' also buffers its output and the `fflush()' function forces `gawk' to flush its buffers. - `fflush()' was added to Brian Kernighan's version of `awk' in - April of 1992. For two decades, it was not part of the POSIX - standard. As of December, 2012, it was accepted for inclusion - into the POSIX standard. See the Austin Group website + `fflush()' was added to BWK `awk' in April of 1992. For two + decades, it was not part of the POSIX standard. As of December, + 2012, it was accepted for inclusion into the POSIX standard. See + the Austin Group website (http://austingroupbugs.net/view.php?id=634). POSIX standardizes `fflush()' as follows: If there is no argument, @@ -12022,7 +12644,7 @@ parameters are enclosed in square brackets ([ ]): to flush only the standard output. `fflush()' returns zero if the buffer is successfully flushed; - otherwise, it returns non-zero (`gawk' returns -1). In the case + otherwise, it returns non-zero. (`gawk' returns -1.) In the case where all buffers are flushed, the return value is zero only if all buffers were flushed successfully. Otherwise, it is -1, and `gawk' warns about the problem FILENAME. @@ -12192,7 +12814,7 @@ enclosed in square brackets ([ ]): If DATESPEC does not contain enough elements or if the resulting time is out of range, `mktime()' returns -1. -`strftime([FORMAT [, TIMESTAMP [, UTC-FLAG]]])' +`strftime(' [FORMAT [`,' TIMESTAMP [`,' UTC-FLAG] ] ]`)' Format the time specified by TIMESTAMP based on the contents of the FORMAT string and return the result. It is similar to the function of the same name in ISO C. If UTC-FLAG is present and is @@ -12272,11 +12894,11 @@ the following date format specifications: `%g' The year modulo 100 of the ISO 8601 week number, as a decimal - number (00-99). For example, January 1, 1993 is in week 53 of - 1992. Thus, the year of its ISO 8601 week number is 1992, even - though its year is 1993. Similarly, December 31, 1973 is in week - 1 of 1974. Thus, the year of its ISO week number is 1974, even - though its year is 1973. + number (00-99). For example, January 1, 2012 is in week 53 of + 2011. Thus, the year of its ISO 8601 week number is 2011, even + though its year is 2012. Similarly, December 31, 2012 is in week + 1 of 2013. Thus, the year of its ISO week number is 2013, even + though its year is 2012. `%G' The full year of the ISO week number, as a decimal number. @@ -12356,7 +12978,7 @@ the following date format specifications: The year modulo 100 as a decimal number (00-99). `%Y' - The full year as a decimal number (e.g., 2011). + The full year as a decimal number (e.g., 2015). `%z' The timezone offset in a +HHMM format (e.g., the format necessary @@ -12378,15 +13000,6 @@ the following date format specifications: If a conversion specifier is not one of the above, the behavior is undefined.(6) - Informally, a "locale" is the geographic place in which a program is -meant to run. For example, a common way to abbreviate the date -September 4, 2012 in the United States is "9/4/12." In many countries -in Europe, however, it is abbreviated "4.9.12." Thus, the `%x' -specification in a `"US"' locale might produce `9/4/12', while in a -`"EUROPE"' locale, it might produce `4.9.12'. The ISO C standard -defines a default `"C"' locale, which is an environment that is typical -of what many C programmers are used to. - For systems that are not yet fully standards-compliant, `gawk' supplies a copy of `strftime()' from the GNU C Library. It supports all of the just-listed format specifications. If that version is used @@ -12416,7 +13029,7 @@ to the standard output and interprets the current time according to the format specifiers in the string. For example: $ date '+Today is %A, %B %d, %Y.' - -| Today is Wednesday, March 30, 2011. + -| Today is Monday, May 05, 2014. Here is the `gawk' version of the `date' utility. It has a shell "wrapper" to handle the `-u' option, which requires that `date' run as @@ -12433,7 +13046,7 @@ if the time zone is set to UTC: esac gawk 'BEGIN { - format = "%a %b %e %H:%M:%S %Z %Y" + format = PROCINFO["strftime"] exitval = 0 if (ARGC > 2) @@ -12494,7 +13107,7 @@ table-bitwise-ops::. 0 | 0 0 | 0 1 | 0 1 1 | 0 1 | 1 1 | 1 0 -Table 9.6: Bitwise Operations +Table 9.5: Bitwise Operations As you can see, the result of an AND operation is 1 only when _both_ bits are 1. The result of an OR operation is 1 if _either_ bit is 1. @@ -12510,23 +13123,23 @@ again with `10111001' and shift it left by three bits, you end up with `11001000'. `gawk' provides built-in functions that implement the bitwise operations just described. They are: -`and(V1, V2 [, ...])' +``and(V1, V2' [`,' ...]`)'' Return the bitwise AND of the arguments. There must be at least two. -`compl(VAL)' +``compl(VAL)'' Return the bitwise complement of VAL. -`lshift(VAL, COUNT)' +``lshift(VAL, COUNT)'' Return the value of VAL, shifted left by COUNT bits. -`or(V1, V2 [, ...])' +``or(V1, V2' [`,' ...]`)'' Return the bitwise OR of the arguments. There must be at least two. -`rshift(VAL, COUNT)' +``rshift(VAL, COUNT)'' Return the value of VAL, shifted right by COUNT bits. -`xor(V1, V2 [, ...])' +``xor(V1, V2' [`,' ...]`)'' Return the bitwise XOR of the arguments. There must be at least two. @@ -12611,8 +13224,8 @@ File: gawk.info, Node: Type Functions, Next: I18N Functions, Prev: Bitwise Fu `gawk' provides a single function that lets you distinguish an array from a scalar variable. This is necessary for writing code that -traverses every element of a true multidimensional array (*note Arrays -of Arrays::). +traverses every element of an array of arrays. (*note Arrays of +Arrays::). `isarray(X)' Return a true value if X is an array. Otherwise return false. @@ -12642,7 +13255,7 @@ descriptions here are purposely brief. *Note Internationalization::, for the full story. Optional parameters are enclosed in square brackets ([ ]): -`bindtextdomain(DIRECTORY [, DOMAIN])' +`bindtextdomain(DIRECTORY' [`,' DOMAIN]`)' Set the directory in which `gawk' will look for message translation files, in case they will not or cannot be placed in the "standard" locations (e.g., during testing). It returns the @@ -12652,13 +13265,13 @@ brackets ([ ]): the null string (`""'), then `bindtextdomain()' returns the current binding for the given DOMAIN. -`dcgettext(STRING [, DOMAIN [, CATEGORY]])' +`dcgettext(STRING' [`,' DOMAIN [`,' CATEGORY] ]`)' Return the translation of STRING in text domain DOMAIN for locale category CATEGORY. The default value for DOMAIN is the current value of `TEXTDOMAIN'. The default value for CATEGORY is `"LC_MESSAGES"'. -`dcngettext(STRING1, STRING2, NUMBER [, DOMAIN [, CATEGORY]])' +`dcngettext(STRING1, STRING2, NUMBER' [`,' DOMAIN [`,' CATEGORY] ]`)' Return the plural form used for NUMBER of the translation of STRING1 and STRING2 in text domain DOMAIN for locale category CATEGORY. STRING1 is the English singular variant of a message, @@ -12692,7 +13305,10 @@ File: gawk.info, Node: Definition Syntax, Next: Function Example, Up: User-de 9.2.1 Function Definition Syntax -------------------------------- -Definitions of functions can appear anywhere between the rules of an + It's entirely fair to say that the `awk' syntax for local variable + definitions is appallingly awful. -- Brian Kernighan + + Definitions of functions can appear anywhere between the rules of an `awk' program. Thus, the general form of an `awk' program is extended to include sequences of rules _and_ user-defined function definitions. There is no need to put the definition of a function before all uses of @@ -12701,28 +13317,35 @@ starting to execute any of it. The definition of a function named NAME looks like this: - function NAME([PARAMETER-LIST]) - { + `function' NAME`('[PARAMETER-LIST]`)' + `{' BODY-OF-FUNCTION - } + `}' Here, NAME is the name of the function to define. A valid function name is like a valid variable name: a sequence of letters, digits, and -underscores that doesn't start with a digit. Within a single `awk' -program, any particular name can only be used as a variable, array, or -function. +underscores that doesn't start with a digit. Here too, only the 52 +upper- and lowercase English letters may be used in a function name. +Within a single `awk' program, any particular name can only be used as +a variable, array, or function. PARAMETER-LIST is an optional list of the function's arguments and local variable names, separated by commas. When the function is called, the argument names are used to hold the argument values given in the -call. The local variables are initialized to the empty string. A -function cannot have two parameters with the same name, nor may it have -a parameter with the same name as the function itself. +call. + + A function cannot have two parameters with the same name, nor may it +have a parameter with the same name as the function itself. In +addition, according to the POSIX standard, function parameters cannot +have the same name as one of the special built-in variables (*note +Built-in Variables::). Not all versions of `awk' enforce this +restriction. - In addition, according to the POSIX standard, function parameters -cannot have the same name as one of the special built-in variables -(*note Built-in Variables::. Not all versions of `awk' enforce this -restriction.) + Local variables act like the empty string if referenced where a +string value is required, and like zero if referenced where a numeric +value is required. This is the same as regular variables that have +never been assigned a value. (There is more to understand about local +variables; *note Dynamic Typing::.) The BODY-OF-FUNCTION consists of `awk' statements. It is the most important part of the definition, because it says what the function @@ -12823,7 +13446,8 @@ this program, using our function to format the results, prints: 5.6 21.2 - This function deletes all the elements in an array: + This function deletes all the elements in an array (recall that the +extra whitespace signifies the start of the local variable list): function delarray(a, i) { @@ -12842,22 +13466,22 @@ standard.) The following is an example of a recursive function. It takes a string as an input parameter and returns the string in backwards order. Recursive functions must always have a test that stops the recursion. -In this case, the recursion terminates when the starting position is -zero, i.e., when there are no more characters left in the string. +In this case, the recursion terminates when the input string is already +empty. - function rev(str, start) + function rev(str) { - if (start == 0) + if (str == "") return "" - return (substr(str, start, 1) rev(str, start - 1)) + return (rev(substr(str, 2)) substr(str, 1, 1)) } If this function is in a file named `rev.awk', it can be tested this way: $ echo "Don't Panic!" | - > gawk --source '{ print rev($0, length($0)) }' -f rev.awk + > gawk -e '{ print rev($0) }' -f rev.awk -| !cinaP t'noD The C `ctime()' function takes a timestamp and returns it in a @@ -12871,7 +13495,7 @@ an `awk' version of `ctime()': function ctime(ts, format) { - format = "%a %b %e %H:%M:%S %Z %Y" + format = PROCINFO["strftime"] if (ts == 0) ts = systime() # use current time as default return strftime(format, ts) @@ -12925,9 +13549,10 @@ File: gawk.info, Node: Variable Scope, Next: Pass By Value/Reference, Prev: C 9.2.3.2 Controlling Variable Scope .................................. -There is no way to make a variable local to a `{ ... }' block in `awk', -but you can make a variable local to a function. It is good practice to -do so whenever a variable is needed only in that function. +Unlike many languages, there is no way to make a variable local to a +`{' ... `}' block in `awk', but you can make a variable local to a +function. It is good practice to do so whenever a variable is needed +only in that function. To make a variable local to a function, simply declare the variable as an argument after the actual function arguments (*note Definition @@ -13106,8 +13731,8 @@ function _are_ visible outside that function. a[1], a[2], a[3] } - prints `a[1] = 1, a[2] = two, a[3] = 3', because `changeit' stores - `"two"' in the second element of `a'. + prints `a[1] = 1, a[2] = two, a[3] = 3', because `changeit()' + stores `"two"' in the second element of `a'. Some `awk' implementations allow you to call a function that has not been defined. They only report a problem at runtime when the program @@ -13146,11 +13771,11 @@ control to the calling part of the `awk' program. It can also be used to return a value for use in the rest of the `awk' program. It looks like this: - return [EXPRESSION] + `return' [EXPRESSION] The EXPRESSION part is optional. Due most likely to an oversight, POSIX does not define what the return value is if you omit the -EXPRESSION. Technically speaking, this make the returned value +EXPRESSION. Technically speaking, this makes the returned value undefined, and therefore, unpredictable. In practice, though, all versions of `awk' simply return the null string, which acts like zero if used in a numeric context. @@ -13244,19 +13869,19 @@ Here is an annotated sample program: } In this example, the first call to `foo()' generates a fatal error, -so `gawk' will not report the second error. If you comment out that -call, though, then `gawk' will report the second error. +so `awk' will not report the second error. If you comment out that +call, though, then `awk' does report the second error. Usually, such things aren't a big issue, but it's worth being aware of them. -File: gawk.info, Node: Indirect Calls, Prev: User-defined, Up: Functions +File: gawk.info, Node: Indirect Calls, Next: Functions Summary, Prev: User-defined, Up: Functions 9.3 Indirect Function Calls =========================== -This section describes a `gawk'-specific extension. +This section describes an advanced, `gawk'-specific extension. Often, you may wish to defer the choice of function to call until runtime. For example, you may have different kinds of records, each of @@ -13295,7 +13920,7 @@ your test scores: This style of programming works, but can be awkward. With "indirect" function calls, you tell `gawk' to use the _value_ of a variable as the -name of the function to call. +_name_ of the function to call. The syntax is similar to that of a regular function call: an identifier immediately followed by a left parenthesis, any arguments, @@ -13337,7 +13962,6 @@ using indirect function calls. Otherwise they perform the expected computations and are not unusual. # For each record, print the class name and the requested statistics - { class_name = $1 gsub(/_/, " ", class_name) # Replace _ with spaces @@ -13524,11 +14148,11 @@ names of the two comparison functions: Remember that you must supply a leading `@' in front of an indirect function call. - Unfortunately, indirect function calls cannot be used with the -built-in functions. However, you can generally write "wrapper" -functions which call the built-in ones, and those can be called -indirectly. (Other than, perhaps, the mathematical functions, there is -not a lot of reason to try to call the built-in functions indirectly.) + Starting with version 4.1.2 of `gawk', indirect function calls may +also be used with built-in functions and with extension functions +(*note Dynamic Extensions::). The only thing you cannot do is pass a +regular expression constant to a built-in function through an indirect +function call.(1) `gawk' does its best to make indirect function calls efficient. For example, in the following case: @@ -13536,7 +14160,70 @@ example, in the following case: for (i = 1; i <= n; i++) @the_func() -`gawk' will look up the actual function to call only once. +`gawk' looks up the actual function to call only once. + + ---------- Footnotes ---------- + + (1) This may change in a future version; recheck the documentation +that comes with your version of `gawk' to see if it has. + + +File: gawk.info, Node: Functions Summary, Prev: Indirect Calls, Up: Functions + +9.4 Summary +=========== + + * `awk' provides built-in functions and lets you define your own + functions. + + * POSIX `awk' provides three kinds of built-in functions: numeric, + string, and I/O. `gawk' provides functions that work with values + representing time, do bit manipulation, sort arrays, and + internationalize and localize programs. `gawk' also provides + several extensions to some of standard functions, typically in the + form of additional arguments. + + * Functions accept zero or more arguments and return a value. The + expressions that provide the argument values are completely + evaluated before the function is called. Order of evaluation is + not defined. The return value can be ignored. + + * The handling of backslash in `sub()' and `gsub()' is not simple. + It is more straightforward in `gawk''s `gensub()' function, but + that function still requires care in its use. + + * User-defined functions provide important capabilities but come with + some syntactic inelegancies. In a function call, there cannot be + any space between the function name and the opening left + parenthesis of the argument list. Also, there is no provision for + local variables, so the convention is to add extra parameters, and + to separate them visually from the real parameters by extra + whitespace. + + * User-defined functions may call other user-defined (and built-in) + functions and may call themselves recursively. Function parameters + "hide" any global variables of the same names. You cannot use the + name of a reserved variable (such as `ARGC') as the name of a + parameter in user-defined functions. + + * Scalar values are passed to user-defined functions by value. Array + parameters are passed by reference; any changes made by the + function to array parameters are thus visible after the function + has returned. + + * Use the `return' statement to return from a user-defined function. + An optional expression becomes the function's return value. Only + scalar values may be returned by a function. + + * If a variable that has never been used is passed to a user-defined + function, how that function treats the variable can set its nature: + either scalar or array. + + * `gawk' provides indirect function calls using a special syntax. + By setting a variable to the name of a function, you can determine + at runtime what function will be called at that point in the + program. This is equivalent to function pointers in C and C++. + File: gawk.info, Node: Library Functions, Next: Sample Programs, Prev: Functions, Up: Top @@ -13563,7 +14250,7 @@ P.J. Plauger wrote: In fact, they felt this idea was so important that they placed this statement on the cover of their book. Because we believe strongly that their statement is correct, this major node and *note Sample -Programs::, provide a good-sized body of code for you to read, and we +Programs::, provide a good-sized body of code for you to read and, we hope, to learn from. This major node presents a library of useful `awk' functions. Many @@ -13614,6 +14301,8 @@ for different implementations of `awk' is pretty straightforward. * Passwd Functions:: Functions for getting user information. * Group Functions:: Functions for getting group information. * Walking Arrays:: A function to walk arrays of arrays. +* Library Functions Summary:: Summary of library functions. +* Library Exercises:: Exercises. ---------- Footnotes ---------- @@ -13740,7 +14429,7 @@ versions of `awk': # mystrtonum --- convert string to number - function mystrtonum(str, ret, chars, n, i, k, c) + function mystrtonum(str, ret, n, i, k, c) { if (str ~ /^0[0-7]*$/) { # octal @@ -13748,12 +14437,13 @@ versions of `awk': ret = 0 for (i = 1; i <= n; i++) { c = substr(str, i, 1) - if ((k = index("01234567", c)) > 0) - k-- # adjust for 1-basing in awk + # index() returns 0 if c not in string, + # includes c == "0" + k = index("1234567", c) ret = ret * 8 + k } - } else if (str ~ /^0[xX][[:xdigit:]]+/) { + } else if (str ~ /^0[xX][[:xdigit:]]+$/) { # hexadecimal str = substr(str, 3) # lop off leading 0x n = length(str) @@ -13761,10 +14451,9 @@ versions of `awk': for (i = 1; i <= n; i++) { c = substr(str, i, 1) c = tolower(c) - if ((k = index("0123456789", c)) > 0) - k-- # adjust for 1-basing in awk - else if ((k = index("abcdef", c)) > 0) - k += 9 + # index() returns 0 if c not in string, + # includes c == "0" + k = index("123456789abcdef", c) ret = ret * 16 + k } @@ -14044,8 +14733,7 @@ worrying about: } #### test code #### - # BEGIN \ - # { + # BEGIN { # for (;;) { # printf("enter a character: ") # if (getline var <= 0) @@ -14164,7 +14852,7 @@ current time formatted in the same way as the `date' utility: now = systime() # return date(1)-style output - ret = strftime("%a %b %e %H:%M:%S %Z %Y", now) + ret = strftime(PROCINFO["strftime"], now) # clear out target array delete time @@ -14414,7 +15102,9 @@ presented in *note Filetrans Function::, to either update `ARGIND' on your own or modify this code as appropriate. The `rewind()' function also relies on the `nextfile' keyword (*note -Nextfile Statement::). +Nextfile Statement::). Because of this, you should not call it from an +`ENDFILE' rule. (This isn't necessary anyway, since as soon as an +`ENDFILE' rule finishes `gawk' goes to the next file!) File: gawk.info, Node: File Checking, Next: Empty Files, Prev: Rewind Function, Up: Data File Management @@ -14424,8 +15114,8 @@ File: gawk.info, Node: File Checking, Next: Empty Files, Prev: Rewind Functio Normally, if you give `awk' a data file that isn't readable, it stops with a fatal error. There are times when you might want to just ignore -such files and keep going. You can do this by prepending the following -program to your `awk' program: +such files and keep going.(1) You can do this by prepending the +following program to your `awk' program: # readable.awk --- library file to skip over unreadable files @@ -14445,10 +15135,16 @@ program to your `awk' program: element from `ARGV' with `delete' skips the file (since it's no longer in the list). See also *note ARGC and ARGV::. + ---------- Footnotes ---------- + + (1) The `BEGINFILE' special pattern (*note BEGINFILE/ENDFILE::) +provides an alternative mechanism for dealing with files that can't be +opened. However, the code here provides a portable solution. + File: gawk.info, Node: Empty Files, Next: Ignoring Assigns, Prev: File Checking, Up: Data File Management -10.3.4 Checking For Zero-length Files +10.3.4 Checking for Zero-length Files ------------------------------------- All known `awk' implementations silently skip over zero-length files. @@ -14496,12 +15192,6 @@ normal case. end of the command-line arguments. Note that the test in the condition of the `for' loop uses the `<=' operator, not `<'. - As an exercise, you might consider whether this same problem can be -solved without relying on `gawk''s `ARGIND' variable. - - As a second exercise, revise this code to handle the case where an -intervening value in `ARGV' is a variable assignment. - File: gawk.info, Node: Ignoring Assigns, Prev: Empty Files, Up: Data File Management @@ -14711,8 +15401,7 @@ not an option, and it ends option processing. Continuing on: i = index(options, thisopt) if (i == 0) { if (Opterr) - printf("%c -- invalid option\n", - thisopt) > "/dev/stderr" + printf("%c -- invalid option\n", thisopt) > "/dev/stderr" if (_opti >= length(argv[Optind])) { Optind++ _opti = 0 @@ -14793,7 +15482,7 @@ is in `ARGV[0]': # test program if (_getopt_test) { while ((_go_c = getopt(ARGC, ARGV, "ab:cd")) != -1) - printf("c = <%c>, optarg = <%s>\n", + printf("c = <%c>, Optarg = <%s>\n", _go_c, Optarg) printf("non-option arguments:\n") for (; Optind < ARGC; Optind++) @@ -14806,17 +15495,17 @@ is in `ARGV[0]': result of two sample runs of the test program: $ awk -f getopt.awk -v _getopt_test=1 -- -a -cbARG bax -x - -| c = <a>, optarg = <> - -| c = <c>, optarg = <> - -| c = <b>, optarg = <ARG> + -| c = <a>, Optarg = <> + -| c = <c>, Optarg = <> + -| c = <b>, Optarg = <ARG> -| non-option arguments: -| ARGV[3] = <bax> -| ARGV[4] = <-x> $ awk -f getopt.awk -v _getopt_test=1 -- -a -x -- xyz abc - -| c = <a>, optarg = <> + -| c = <a>, Optarg = <> error--> x -- invalid option - -| c = <?>, optarg = <> + -| c = <?>, Optarg = <> -| non-option arguments: -| ARGV[4] = <xyz> -| ARGV[5] = <abc> @@ -14875,7 +15564,7 @@ that "cats" the password database: /* * pwcat.c * - * Generate a printable version of the password database + * Generate a printable version of the password database. */ #include <stdio.h> #include <pwd.h> @@ -15100,7 +15789,7 @@ group database, is as follows: /* * grcat.c * - * Generate a printable version of the group database + * Generate a printable version of the group database. */ #include <stdio.h> #include <grp.h> @@ -15136,9 +15825,10 @@ Group Password used; it is usually empty or set to `*'. Group ID Number - The group's numeric group ID number; this number must be unique - within the file. (On some systems it's a C `long', and not an - `int'. Thus we cast it to `long' for all cases.) + The group's numeric group ID number; the association of name to + number must be unique within the file. (On some systems it's a C + `long', and not an `int'. Thus we cast it to `long' for all + cases.) Group Member List A comma-separated list of user names. These users are members of @@ -15165,8 +15855,7 @@ the same names: # group.awk --- functions for dealing with the group file - BEGIN \ - { + BEGIN { # Change to suit your system _gr_awklib = "/usr/local/libexec/awk/" } @@ -15242,15 +15931,12 @@ the database for the same group. This is common when a group has a large number of members. A pair of such entries might look like the following: - tvpeople:*:101:johnny,jay,arsenio + tvpeople:*:101:johny,jay,arsenio tvpeople:*:101:david,conan,tom,joan For this reason, `_gr_init()' looks to see if a group name or group ID number is already seen. If it is, then the user names are simply -concatenated onto the previous list of users. (There is actually a -subtle problem with the code just presented. Suppose that the first -time there were no names. This code adds the names with a leading -comma. It also doesn't check that there is a `$4'.) +concatenated onto the previous list of users.(1) Finally, `_gr_init()' closes the pipeline to `grcat', restores `FS' (and `FIELDWIDTHS' or `FPAT' if necessary), `RS', and `$0', initializes @@ -15315,8 +16001,14 @@ very simple, relying on `awk''s associative arrays to do work. The `id' program in *note Id Program::, uses these functions. + ---------- Footnotes ---------- + + (1) There is actually a subtle problem with the code just presented. +Suppose that the first time there were no names. This code adds the +names with a leading comma. It also doesn't check that there is a `$4'. + -File: gawk.info, Node: Walking Arrays, Prev: Group Functions, Up: Library Functions +File: gawk.info, Node: Walking Arrays, Next: Library Functions Summary, Prev: Group Functions, Up: Library Functions 10.7 Traversing Arrays of Arrays ================================ @@ -15366,17 +16058,73 @@ value. Here is a main program to demonstrate: -| a[2][2] = 22 -| a[3] = 3 - Walking an array and processing each element is a general-purpose -operation. You might want to consider generalizing the `walk_array()' -function by adding an additional parameter named `process'. + +File: gawk.info, Node: Library Functions Summary, Next: Library Exercises, Prev: Walking Arrays, Up: Library Functions + +10.8 Summary +============ + + * Reading programs is an excellent way to learn Good Programming. + The functions provided in this major node and the next are intended + to serve that purpose. + + * When writing general-purpose library functions, put some thought + into how to name any global variables so that they won't conflict + with variables from a user's program. + + * The functions presented here fit into the following categories: + + General problems + Number to string conversion, assertions, rounding, random + number generation, converting characters to numbers, joining + strings, getting easily usable time-of-day information, and + reading a whole file in one shot. - Then, inside the loop, instead of simply printing the array element's -index and value, use the indirect function call syntax (*note Indirect -Calls::) on `process', passing it the index and the value. + Managing data files + Noting data file boundaries, rereading the current file, + checking for readable files, checking for zero-length files, + and treating assignments as file names. + + Processing command-line options + An `awk' version of the standard C `getopt()' function. + + Reading the user and group databases + Two sets of routines that parallel the C library versions. + + Traversing arrays of arrays + A simple function to traverse an array of arrays to any depth. + + + +File: gawk.info, Node: Library Exercises, Prev: Library Functions Summary, Up: Library Functions + +10.9 Exercises +============== + + 1. In *note Empty Files::, we presented the `zerofile.awk' program, + which made use of `gawk''s `ARGIND' variable. Can this problem be + solved without relying on `ARGIND'? If so, how? + + 2. As a related challenge, revise that code to handle the case where + an intervening value in `ARGV' is a variable assignment. + + 3. *note Walking Arrays::, presented a function that walked a + multidimensional array to print it out. However, walking an array + and processing each element is a general-purpose operation. + Generalize the `walk_array()' function by adding an additional + parameter named `process'. + + Then, inside the loop, instead of printing the array element's + index and value, use the indirect function call syntax (*note + Indirect Calls::) on `process', passing it the index and the value. + + When calling `walk_array()', you would pass the name of a + user-defined function that expects to receive an index and a value, + and then processes the element. + + Test your new version by printing the array; you should end up with + output identical to that of the original version. - When calling `walk_array()', you would pass the name of a -user-defined function that expects to receive an index and a value, and -then processes the element. File: gawk.info, Node: Sample Programs, Next: Advanced Features, Prev: Library Functions, Up: Top @@ -15397,6 +16145,8 @@ Library Functions::. * Running Examples:: How to run these examples. * Clones:: Clones of common utilities. * Miscellaneous Programs:: Some interesting `awk' programs. +* Programs Summary:: Summary of programs. +* Programs Exercises:: Exercises. File: gawk.info, Node: Running Examples, Next: Clones, Up: Sample Programs @@ -15528,8 +16278,7 @@ through the command-line options. Exactly one of the variables should be done by fields or by characters, respectively. When cutting by characters, the output field separator is set to the null string: - BEGIN \ - { + BEGIN { FS = "\t" # default OFS = FS while ((c = getopt(ARGC, ARGV, "sf:c:d:")) != -1) { @@ -15542,7 +16291,7 @@ by characters, the output field separator is set to the null string: OFS = "" } else if (c == "d") { if (length(Optarg) > 1) { - printf("Using first character of %s" \ + printf("cut: using first character of %s" \ " for delimiter\n", Optarg) > "/dev/stderr" Optarg = substr(Optarg, 1, 1) } @@ -15551,7 +16300,7 @@ by characters, the output field separator is set to the null string: if (FS == " ") # defeat awk semantics FS = "[ ]" } else if (c == "s") - suppress++ + suppress = 1 else usage() } @@ -15609,7 +16358,7 @@ splitting: if (index(f[i], "-") != 0) { # a range m = split(f[i], g, "-") if (m != 2 || g[1] >= g[2]) { - printf("bad field list: %s\n", + printf("cut: bad field list: %s\n", f[i]) > "/dev/stderr" exit 1 } @@ -15647,7 +16396,7 @@ filler fields: if (index(f[i], "-") != 0) { # range m = split(f[i], g, "-") if (m != 2 || g[1] >= g[2]) { - printf("bad character list: %s\n", + printf("cut: bad character list: %s\n", f[i]) > "/dev/stderr" exit 1 } @@ -15720,7 +16469,7 @@ The `egrep' utility searches files for patterns. It uses regular expressions that are almost identical to those available in `awk' (*note Regexp::). You invoke it as follows: - egrep [ OPTIONS ] 'PATTERN' FILES ... + `egrep' [OPTIONS] `'PATTERN'' FILES ... The PATTERN is a regular expression. In typical usage, the regular expression is quoted to prevent the shell from expanding any of the @@ -15864,6 +16613,11 @@ know the total number of lines that matched the pattern: total += fcount } + The `BEGINFILE' and `ENDFILE' special patterns (*note +BEGINFILE/ENDFILE::) could be used, but then the program would be +`gawk'-specific. Additionally, this example was written before `gawk' +acquired `BEGINFILE' and `ENDFILE'. + The following rule does most of the work of matching lines. The variable `matches' is true if the line matched the pattern. If the user wants lines that did not match, the sense of `matches' is inverted @@ -15909,11 +16663,8 @@ line is printed, with a leading file name and colon if necessary: The `END' rule takes care of producing the correct exit status. If there are no matches, the exit status is one; otherwise it is zero: - END \ - { - if (total == 0) - exit 1 - exit 0 + END { + exit (total == 0) } The `usage()' function prints a usage message in case of invalid @@ -15930,13 +16681,6 @@ options, and then exits: The variable `e' is used so that the function fits nicely on the printed page. - Just a note on programming style: you may have noticed that the `END' -rule uses backslash continuation, with the open brace on a line by -itself. This is so that it more closely resembles the way functions -are written. Many of the examples in this major node use this style. -You can decide for yourself if you like writing your `BEGIN' and `END' -rules this way or not. - ---------- Footnotes ---------- (1) It also introduces a subtle bug; if a match happens, we output @@ -15955,7 +16699,7 @@ different from the real ones. If possible, `id' also supplies the corresponding user and group names. The output might look like this: $ id - -| uid=500(arnold) gid=500(arnold) groups=6(disk),7(lp),19(floppy) + -| uid=1000(arnold) gid=1000(arnold) groups=1000(arnold),4(adm),7(lp),27(sudo) This information is part of what is provided by `gawk''s `PROCINFO' array (*note Built-in Variables::). However, the `id' utility provides @@ -15979,8 +16723,7 @@ and the group numbers: # uid=12(foo) euid=34(bar) gid=3(baz) \ # egid=5(blat) groups=9(nine),2(two),1(one) - BEGIN \ - { + BEGIN { uid = PROCINFO["uid"] euid = PROCINFO["euid"] gid = PROCINFO["gid"] @@ -15988,34 +16731,26 @@ and the group numbers: printf("uid=%d", uid) pw = getpwuid(uid) - if (pw != "") { - split(pw, a, ":") - printf("(%s)", a[1]) - } + if (pw != "") + pr_first_field(pw) if (euid != uid) { printf(" euid=%d", euid) pw = getpwuid(euid) - if (pw != "") { - split(pw, a, ":") - printf("(%s)", a[1]) - } + if (pw != "") + pr_first_field(pw) } printf(" gid=%d", gid) pw = getgrgid(gid) - if (pw != "") { - split(pw, a, ":") - printf("(%s)", a[1]) - } + if (pw != "") + pr_first_field(pw) if (egid != gid) { printf(" egid=%d", egid) pw = getgrgid(egid) - if (pw != "") { - split(pw, a, ":") - printf("(%s)", a[1]) - } + if (pw != "") + pr_first_field(pw) } for (i = 1; ("group" i) in PROCINFO; i++) { @@ -16024,10 +16759,8 @@ and the group numbers: group = PROCINFO["group" i] printf("%d", group) pw = getgrgid(group) - if (pw != "") { - split(pw, a, ":") - printf("(%s)", a[1]) - } + if (pw != "") + pr_first_field(pw) if (("group" (i+1)) in PROCINFO) printf(",") } @@ -16035,6 +16768,12 @@ and the group numbers: print "" } + function pr_first_field(str, a) + { + split(str, a, ":") + printf("(%s)", a[1]) + } + The test in the `for' loop is worth noting. Any supplementary groups in the `PROCINFO' array have the indices `"group1"' through `"groupN"' for some N, i.e., the total number of supplementary groups. @@ -16049,6 +16788,10 @@ the last group in the array and the loop exits. then the condition is false the first time it's tested, and the loop body never executes. + The `pr_first_field()' function simply isolates out some code that +is used repeatedly, making the whole program slightly shorter and +cleaner. + File: gawk.info, Node: Split Program, Next: Tee Program, Prev: Id Program, Up: Clones @@ -16058,7 +16801,7 @@ File: gawk.info, Node: Split Program, Next: Tee Program, Prev: Id Program, U The `split' program splits large text files into smaller pieces. Usage is as follows:(1) - split [-COUNT] file [ PREFIX ] + `split' [`-COUNT'] [FILE] [PREFIX] By default, the output files are named `xaa', `xab', and so on. Each file has 1000 lines in it, with the likely exception of the last file. @@ -16082,7 +16825,7 @@ output file names: # split.awk --- do split in awk # # Requires ord() and chr() library functions - # usage: split [-num] [file] [outname] + # usage: split [-count] [file] [outname] BEGIN { outfile = "x" # default @@ -16091,7 +16834,7 @@ output file names: usage() i = 1 - if (ARGV[i] ~ /^-[[:digit:]]+$/) { + if (i in ARGV && ARGV[i] ~ /^-[[:digit:]]+$/) { count = -ARGV[i] ARGV[i] = "" i++ @@ -16167,7 +16910,7 @@ The `tee' program is known as a "pipe fitting." `tee' copies its standard input to its standard output and also duplicates it to the files named on the command line. Its usage is as follows: - tee [-a] file ... + `tee' [`-a'] FILE ... The `-a' option tells `tee' to append to the named files, instead of truncating them and starting over. @@ -16188,8 +16931,7 @@ input by setting `ARGV[1]' to `"-"' and `ARGC' to two: # Copy standard input to all named output files. # Append content if -a option is supplied. # - BEGIN \ - { + BEGIN { for (i = 1; i < ARGC; i++) copy[i] = ARGV[i] @@ -16239,8 +16981,7 @@ N input records and M output files, the first method only executes N Finally, the `END' rule cleans up by closing all the output files: - END \ - { + END { for (i in copy) close(copy[i]) } @@ -16256,7 +16997,7 @@ and by default removes duplicate lines. In other words, it only prints unique lines--hence the name. `uniq' has a number of options. The usage is as follows: - uniq [-udc [-N]] [+N] [ INPUT FILE [ OUTPUT FILE ]] + `uniq' [`-udc' [`-N']] [`+N'] [INPUTFILE [OUTPUTFILE]] The options for `uniq' are: @@ -16279,11 +17020,11 @@ usage is as follows: Skip N characters before comparing lines. Any fields specified with `-N' are skipped first. -`INPUT FILE' +`INPUTFILE' Data is read from the input file named on the command line, instead of from the standard input. -`OUTPUT FILE' +`OUTPUTFILE' The generated output is sent to the named output file, instead of to the standard output. @@ -16327,8 +17068,7 @@ standard output, `/dev/stdout': # -n skip n fields # +n skip n characters, skip fields first - BEGIN \ - { + BEGIN { count = 1 outputfile = "/dev/stdout" opts = "udc0:1:2:3:4:5:6:7:8:9:" @@ -16340,7 +17080,7 @@ standard output, `/dev/stdout': else if (c == "c") do_count++ else if (index("0123456789", c) != 0) { - # getopt requires args to options + # getopt() requires args to options # this messes us up for things like -5 if (Optarg ~ /^[[:digit:]]+$/) fcount = (c Optarg) + 0 @@ -16473,7 +17213,7 @@ File: gawk.info, Node: Wc Program, Prev: Uniq Program, Up: Clones The `wc' (word count) utility counts lines, words, and characters in one or more input files. Its usage is as follows: - wc [-lwc] [ FILES ... ] + `wc' [`-lwc'] [FILES ...] If no files are specified on the command line, `wc' reads its standard input. If there are multiple files, it also prints total @@ -16553,7 +17293,7 @@ lines, words, and characters to zero, and saves the current file name in } The `endfile()' function adds the current file's numbers to the -running totals of lines, words, and characters.(1) It then prints out +running totals of lines, words, and characters. It then prints out those numbers for the file that was just read. It relies on `beginfile()' to reset the numbers for the following data file: @@ -16572,7 +17312,7 @@ those numbers for the file that was just read. It relies on } There is one rule that is executed for each line. It adds the length -of the record, plus one, to `chars'.(2) Adding one plus the record +of the record, plus one, to `chars'.(1) Adding one plus the record length is needed because the newline character separating records (the value of `RS') is not part of the record itself, and thus not included in its length. Next, `lines' is incremented for each line read, and @@ -16602,15 +17342,11 @@ in its length. Next, `lines' is incremented for each line read, and ---------- Footnotes ---------- - (1) `wc' can't just use the value of `FNR' in `endfile()'. If you -examine the code in *note Filetrans Function::, you will see that `FNR' -has already been reset by the time `endfile()' is called. - - (2) Since `gawk' understands multibyte locales, this code counts + (1) Since `gawk' understands multibyte locales, this code counts characters, not bytes. -File: gawk.info, Node: Miscellaneous Programs, Prev: Clones, Up: Sample Programs +File: gawk.info, Node: Miscellaneous Programs, Next: Programs Summary, Prev: Clones, Up: Sample Programs 11.3 A Grab Bag of `awk' Programs ================================= @@ -16720,8 +17456,7 @@ Statement::), but the processing could be done with a series of # Requires getlocaltime() library function # usage: alarm time [ "message" [ count [ delay ] ] ] - BEGIN \ - { + BEGIN { # Initial argument sanity checking usage1 = "usage: alarm time ['message' [count [delay]]]" usage2 = sprintf("\t(%s) time ::= hh:mm", ARGV[1]) @@ -16791,7 +17526,7 @@ alarm: # how long to sleep for naptime = target - current if (naptime <= 0) { - print "time is in the past!" > "/dev/stderr" + print "alarm: time is in the past!" > "/dev/stderr" exit 1 } @@ -16839,11 +17574,11 @@ there are more characters in the "from" list than in the "to" list, the last character of the "to" list is used for the remaining characters in the "from" list. - Some time ago, a user proposed that a transliteration function should -be added to `gawk'. The following program was written to prove that -character transliteration could be done with a user-level function. -This program is not as complete as the system `tr' utility but it does -most of the job. + Once upon a time, a user proposed that a transliteration function +should be added to `gawk'. The following program was written to prove +that character transliteration could be done with a user-level +function. This program is not as complete as the system `tr' utility +but it does most of the job. The `translate' program demonstrates one of the few weaknesses of standard `awk': dealing with individual characters is very painful, @@ -16924,8 +17659,8 @@ record: While it is possible to do character transliteration in a user-level function, it is not necessarily efficient, and we (the `gawk' authors) started to consider adding a built-in function. However, shortly after -writing this program, we learned that the System V Release 4 `awk' had -added the `toupper()' and `tolower()' functions (*note String +writing this program, we learned that Brian Kernighan had added the +`toupper()' and `tolower()' functions to his `awk' (*note String Functions::). These functions handle the vast majority of the cases where character transliteration is necessary, and so we chose to simply add those functions to `gawk' as well and then leave well enough alone. @@ -16935,15 +17670,19 @@ array only once, in a `BEGIN' rule. However, this assumes that the "from" and "to" lists will never change throughout the lifetime of the program. + Another obvious improvement is to enable the use of ranges, such as +`a-z', as allowed by the `tr' utility. Look at the code for `cut.awk' +(*note Cut Program::) for inspiration. + ---------- Footnotes ---------- - (1) On some older systems, including Solaris, `tr' may require that -the lists be written as range expressions enclosed in square brackets -(`[a-z]') and quoted, to prevent the shell from attempting a file name -expansion. This is not a feature. + (1) On some older systems, including Solaris, the system version of +`tr' may require that the lists be written as range expressions +enclosed in square brackets (`[a-z]') and quoted, to prevent the shell +from attempting a file name expansion. This is not a feature. - (2) This program was written before `gawk' acquired the ability to -split each character in a string into separate array elements. + (2) This program was also written before `gawk' acquired the ability +to split each character in a string into separate array elements. File: gawk.info, Node: Labels Program, Next: Word Sorting, Prev: Translate Program, Up: Miscellaneous Programs @@ -17042,8 +17781,7 @@ not have been an even multiple of 20 labels in the data: Count++ } - END \ - { + END { printpage() } @@ -17060,7 +17798,7 @@ File: gawk.info, Node: Word Sorting, Next: History Sorting, Prev: Labels Prog When working with large amounts of text, it can be interesting to know how often different words appear. For example, an author may overuse -certain words, in which case she might wish to find synonyms to +certain words, in which case he or she might wish to find synonyms to substitute for words that appear too often. This node develops a program for counting words and presenting the frequency information in a useful format. @@ -17123,6 +17861,10 @@ script. Here is the new version of the program: printf "%s\t%d\n", word, freq[word] } + The regexp `/[^[:alnum:]_[:blank:]]/' might have been written +`/[[:punct:]]/', but then underscores would also be removed, and we +want to keep them. + Assuming we have saved this program in a file named `wordfreq.awk', and that the data is in `file1', the following pipeline: @@ -17200,8 +17942,7 @@ information. For example, using the following `print' statement in the print data[lines[i]], lines[i] - This works because `data[$0]' is incremented each time a line is -seen. +This works because `data[$0]' is incremented each time a line is seen. File: gawk.info, Node: Extract Program, Next: Simple Sed, Prev: History Sorting, Up: Miscellaneous Programs @@ -17290,7 +18031,7 @@ with a zero exit status, signifying OK: /^@c(omment)?[ \t]+system/ \ { if (NF < 3) { - e = (FILENAME ":" FNR) + e = ("extract: " FILENAME ":" FNR) e = (e ": badly formed `system' line") print e > "/dev/stderr" next @@ -17299,7 +18040,7 @@ with a zero exit status, signifying OK: $2 = "" stat = system($0) if (stat != 0) { - e = (FILENAME ":" FNR) + e = ("extract: " FILENAME ":" FNR) e = (e ": warning: system returned " stat) print e > "/dev/stderr" } @@ -17329,16 +18070,17 @@ function (*note String Functions::). The `@' symbol is used as the separator character. Each element of `a' that is empty indicates two successive `@' symbols in the original line. For each two empty elements (`@@' in the original file), we have to add a single `@' -symbol back in.(1) +symbol back in. When the processing of the array is finished, `join()' is called -with the value of `SUBSEP', to rejoin the pieces back into a single -line. That line is then printed to the output file: +with the value of `SUBSEP' (*note Multidimensional::), to rejoin the +pieces back into a single line. That line is then printed to the +output file: /^@c(omment)?[ \t]+file/ \ { if (NF != 3) { - e = (FILENAME ":" FNR ": badly formed `file' line") + e = ("extract: " FILENAME ":" FNR ": badly formed `file' line") print e > "/dev/stderr" next } @@ -17389,7 +18131,7 @@ closing the open file: function unexpected_eof() { - printf("%s:%d: unexpected EOF or error\n", + printf("extract: %s:%d: unexpected EOF or error\n", FILENAME, FNR) > "/dev/stderr" exit 1 } @@ -17399,11 +18141,6 @@ closing the open file: close(curfile) } - ---------- Footnotes ---------- - - (1) This program was written before `gawk' had the `gensub()' -function. Consider how you might use it to simplify the code. - File: gawk.info, Node: Simple Sed, Next: Igawk Program, Prev: Extract Program, Up: Miscellaneous Programs @@ -17539,8 +18276,8 @@ language.(1) It works as follows: 2. For any arguments that do represent `awk' text, put the arguments into a shell variable that will be expanded. There are two cases: - a. Literal text, provided with `--source' or `--source='. This - text is just appended directly. + a. Literal text, provided with `-e' or `--source'. This text is + just appended directly. b. Source file names, provided with `-f'. We use a neat trick and append `@include FILENAME' to the shell variable's @@ -17580,10 +18317,10 @@ are several cases of interest: programming trick. Don't worry about it if you are not familiar with `sh'.) -`-v, -F' +`-v', `-F' These are saved and passed on to `gawk'. -`-f, --file, --file=, -Wfile=' +`-f', `--file', `--file=', `-Wfile=' The file name is appended to the shell variable `program' with an `@include' statement. The `expr' utility is used to remove the leading option part of the argument (e.g., `--file='). (Typical @@ -17592,10 +18329,10 @@ are several cases of interest: sequences in their arguments, possibly mangling the program text. Using `expr' avoids this problem.) -`--source, --source=, -Wsource=' +`--source', `--source=', `-Wsource=' The source text is appended to `program'. -`--version, -Wversion' +`--version', `-Wversion' `igawk' prints its version number, runs `gawk --version' to get the `gawk' version information, and then exits. @@ -17741,12 +18478,12 @@ which represents the current directory: pathlist[i] = "." } - The stack is initialized with `ARGV[1]', which will be `/dev/stdin'. -The main loop comes next. Input lines are read in succession. Lines -that do not start with `@include' are printed verbatim. If the line -does start with `@include', the file name is in `$2'. `pathto()' is -called to generate the full path. If it cannot, then the program -prints an error message and continues. + The stack is initialized with `ARGV[1]', which will be +`"/dev/stdin"'. The main loop comes next. Input lines are read in +succession. Lines that do not start with `@include' are printed +verbatim. If the line does start with `@include', the file name is in +`$2'. `pathto()' is called to generate the full path. If it cannot, +then the program prints an error message and continues. The next thing to check is if the file is included already. The `processed' array is indexed by the full file name of each included @@ -17769,7 +18506,7 @@ zero, the program is done: } fpath = pathto($2) if (fpath == "") { - printf("igawk:%s:%d: cannot find %s\n", + printf("igawk: %s:%d: cannot find %s\n", input[stackptr], FNR, $2) > "/dev/stderr" continue } @@ -17823,7 +18560,7 @@ supplied. The `eval' command is a shell construct that reruns the shell's parsing process. This keeps things properly quoted. - This version of `igawk' represents my fifth version of this program. + This version of `igawk' represents the fifth version of this program. There are four key simplifications that make the program work better: * Using `@include' even for the files named with `-f' makes building @@ -17853,26 +18590,6 @@ manipulation using the shell than it is in `awk'. Finally, `igawk' shows that it is not always necessary to add new features to a program; they can often be layered on top. - As an additional example of this, consider the idea of having two -files in a directory in the search path: - -`default.awk' - This file contains a set of default library functions, such as - `getopt()' and `assert()'. - -`site.awk' - This file contains library functions that are specific to a site or - installation; i.e., locally developed functions. Having a - separate file allows `default.awk' to change with new `gawk' - releases, without requiring the system administrator to update it - each time by adding the local functions. - - One user suggested that `gawk' be modified to automatically read -these files upon startup. Instead, it would be very simple to modify -`igawk' to do this. Since `igawk' can process nested `@include' -directives, `default.awk' could simply contain `@include' statements -for the desired library functions. - ---------- Footnotes ---------- (1) Fully explaining the `sh' language is beyond the scope of this @@ -17997,7 +18714,141 @@ supplies the following copyright terms: X*(X-x)-o*o,(x+X)*o*o+o,x*(X-x)-O-O,x-O+(O+o+X+x)*(o+O),X*X-X*(x-O)-x+O, O+X*(o*(o+O)+O),+x+O+X*o,x*(x-o),(o+X+x)*o*o-(x-O-O),O+(X-x)*(X+O),x-O}' - We leave it to you to determine what the program does. + We leave it to you to determine what the program does. (If you are +truly desperate to understand it, see Chris Johansen's explanation, +which is embedded in the Texinfo source file for this Info file.) + + +File: gawk.info, Node: Programs Summary, Next: Programs Exercises, Prev: Miscellaneous Programs, Up: Sample Programs + +11.4 Summary +============ + + * The functions provided in this major node and the previous one + continue on the theme that reading programs is an excellent way to + learn Good Programming. + + * Using `#!' to make `awk' programs directly runnable makes them + easier to use. Otherwise, invoke the program using `awk -f ...'. + + * Reimplementing standard POSIX programs in `awk' is a pleasant + exercise; `awk''s expressive power lets you write such programs in + relatively few lines of code, yet they are functionally complete + and usable. + + * One of standard `awk''s weaknesses is working with individual + characters. The ability to use `split()' with the empty string as + the separator can considerably simplify such tasks. + + * The library functions from *note Library Functions::, proved their + usefulness for a number of real (if small) programs. + + * Besides reinventing POSIX wheels, other programs solved a + selection of interesting problems, such as finding duplicates + words in text, printing mailing labels, and finding anagrams. + + + +File: gawk.info, Node: Programs Exercises, Prev: Programs Summary, Up: Sample Programs + +11.5 Exercises +============== + + 1. Rewrite `cut.awk' (*note Cut Program::) using `split()' with `""' + as the seperator. + + 2. In *note Egrep Program::, we mentioned that `egrep -i' could be + simulated in versions of `awk' without `IGNORECASE' by using + `tolower()' on the line and the pattern. In a footnote there, we + also mentioned that this solution has a bug: the translated line is + output, and not the original one. Fix this problem. + + 3. The POSIX version of `id' takes options that control which + information is printed. Modify the `awk' version (*note Id + Program::) to accept the same arguments and perform in the same + way. + + 4. The `split.awk' program (*note Split Program::) assumes that + letters are contiguous in the character set, which isn't true for + EBCDIC systems. Fix this problem. (Hint: Consider a different + way to work through the alphabet, without relying on `ord()' and + `chr()'.) + + 5. In `uniq.awk' (*note Uniq Program::, the logic for choosing which + lines to print represents a "state machine", which is "a device + that can be in one of a set number of stable conditions depending + on its previous condition and on the present values of its + inputs."(1) Brian Kernighan suggests that "an alternative approach + to state mechines is to just read the input into an array, then + use indexing. It's almost always easier code, and for most inputs + where you would use this, just as fast." Rewrite the logic to + follow this suggestion. + + 6. Why can't the `wc.awk' program (*note Wc Program::) just use the + value of `FNR' in `endfile()'? Hint: Examine the code in *note + Filetrans Function::. + + 7. Manipulation of individual characters in the `translate' program + (*note Translate Program::) is painful using standard `awk' + functions. Given that `gawk' can split strings into individual + characters using `""' as the separator, how might you use this + feature to simplify the program? + + 8. The `extract.awk' program (*note Extract Program::) was written + before `gawk' had the `gensub()' function. Use it to simplify the + code. + + 9. Compare the performance of the `awksed.awk' program (*note Simple + Sed::) with the more straightforward: + + BEGIN { + pat = ARGV[1] + repl = ARGV[2] + ARGV[1] = ARGV[2] = "" + } + + { gsub(pat, repl); print } + + 10. What are the advantages and disadvantages of `awksed.awk' versus + the real `sed' utility? + + 11. In *note Igawk Program::, we mentioned that not trying to save the + line read with `getline' in the `pathto()' function when testing + for the file's accessibility for use with the main program + simplifies things considerably. What problem does this engender + though? + + 12. As an additional example of the idea that it is not always + necessary to add new features to a program, consider the idea of + having two files in a directory in the search path: + + `default.awk' + This file contains a set of default library functions, such + as `getopt()' and `assert()'. + + `site.awk' + This file contains library functions that are specific to a + site or installation; i.e., locally developed functions. + Having a separate file allows `default.awk' to change with + new `gawk' releases, without requiring the system + administrator to update it each time by adding the local + functions. + + One user suggested that `gawk' be modified to automatically read + these files upon startup. Instead, it would be very simple to + modify `igawk' to do this. Since `igawk' can process nested + `@include' directives, `default.awk' could simply contain + `@include' statements for the desired library functions. Make + this change. + + 13. Modify `anagram.awk' (*note Anagram Program::), to avoid the use + of the external `sort' utility. + + + ---------- Footnotes ---------- + + (1) This is the definition returned from entering `define: state +machine' into Google. File: gawk.info, Node: Advanced Features, Next: Internationalization, Prev: Sample Programs, Up: Top @@ -18043,6 +18894,7 @@ own: * Two-way I/O:: Two-way communications with another process. * TCP/IP Networking:: Using `gawk' for network programming. * Profiling:: Profiling your `awk' programs. +* Advanced Features Summary:: Summary of advanced features. File: gawk.info, Node: Nondecimal Data, Next: Array Sorting, Up: Advanced Features @@ -18066,8 +18918,8 @@ your data as numeric: The `print' statement treats its expressions as strings. Although the fields can act as numbers when necessary, they are still strings, so -`print' does not try to treat them numerically. You may need to add -zero to a field to force it to be treated as a number. For example: +`print' does not try to treat them numerically. You need to add zero +to a field to force it to be treated as a number. For example: $ echo 0123 123 0x123 | gawk --non-decimal-data ' > { print $1, $2, $3 @@ -18082,7 +18934,7 @@ request it. CAUTION: _Use of this option is not recommended._ It can break old programs very badly. Instead, use the `strtonum()' function to - convert your data (*note Nondecimal-numbers::). This makes your + convert your data (*note String Functions::). This makes your programs easier to write and easier to read, and leads to less surprising results. @@ -18121,7 +18973,7 @@ you do this. *note Controlling Scanning::, describes how you can assign special, pre-defined values to `PROCINFO["sorted_in"]' in order to control the -order in which `gawk' will traverse an array during a `for' loop. +order in which `gawk' traverses an array during a `for' loop. In addition, the value of `PROCINFO["sorted_in"]' can be a function name. This lets you traverse an array based on any custom criterion. @@ -18394,9 +19246,9 @@ become the values of the result array: So far, so good. Now it starts to get interesting. Both `asort()' and `asorti()' accept a third string argument to control comparison of -array elements. In *note String Functions::, we ignored this third -argument; however, the time has now come to describe how this argument -affects these two functions. +array elements. When we introduced `asort()' and `asorti()' in *note +String Functions::, we ignored this third argument; however, now is the +time to describe how this argument affects these two functions. Basically, the third argument specifies how the array is to be sorted. There are two possibilities. As with `PROCINFO["sorted_in"]', @@ -18436,24 +19288,7 @@ File: gawk.info, Node: Two-way I/O, Next: TCP/IP Networking, Prev: Array Sort 12.3 Two-Way Communications with Another Process ================================================ - From: brennan@whidbey.com (Mike Brennan) - Newsgroups: comp.lang.awk - Subject: Re: Learn the SECRET to Attract Women Easily - Date: 4 Aug 1997 17:34:46 GMT - Message-ID: <5s53rm$eca@news.whidbey.com> - - On 3 Aug 1997 13:17:43 GMT, Want More Dates??? - <tracy78@kilgrona.com> wrote: - >Learn the SECRET to Attract Women Easily - > - >The SCENT(tm) Pheromone Sex Attractant For Men to Attract Women - - The scent of awk programmers is a lot more attractive to women than - the scent of perl programmers. - -- - Mike Brennan - - It is often useful to be able to send data to a separate program for +It is often useful to be able to send data to a separate program for processing and then read the result. This can always be done with temporary files: @@ -18472,12 +19307,11 @@ temporary files: This works, but not elegantly. Among other things, it requires that the program be run in a directory that cannot be shared among users; for example, `/tmp' will not do, as another user might happen to be -using a temporary file with the same name. - - However, with `gawk', it is possible to open a _two-way_ pipe to -another process. The second process is termed a "coprocess", since it -runs in parallel with `gawk'. The two-way connection is created using -the `|&' operator (borrowed from the Korn shell, `ksh'):(1) +using a temporary file with the same name.(1) However, with `gawk', it +is possible to open a _two-way_ pipe to another process. The second +process is termed a "coprocess", since it runs in parallel with `gawk'. +The two-way connection is created using the `|&' operator (borrowed +from the Korn shell, `ksh'):(2) do { print DATA |& "subprogram" @@ -18544,7 +19378,8 @@ the `gawk' program. Once all of the data has been read, `gawk' terminates the coprocess and exits. As a side note, the assignment `LC_ALL=C' in the `sort' command -ensures traditional Unix (ASCII) sorting from `sort'. +ensures traditional Unix (ASCII) sorting from `sort'. This is not +strictly necessary here, but it's good to know how to do this. You may also use pseudo-ttys (ptys) for two-way communication instead of pipes, if your system supports them. This is done on a @@ -18556,14 +19391,18 @@ per-command basis, by setting a special element in the `PROCINFO' array print ... |& command # start two-way pipe ... -Using ptys avoids the buffer deadlock issues described earlier, at some -loss in performance. If your system does not have ptys, or if all the -system's ptys are in use, `gawk' automatically falls back to using -regular pipes. +Using ptys usually avoids the buffer deadlock issues described earlier, +at some loss in performance. If your system does not have ptys, or if +all the system's ptys are in use, `gawk' automatically falls back to +using regular pipes. ---------- Footnotes ---------- - (1) This is very different from the same operator in the C shell and + (1) Michael Brennan suggests the use of `rand()' to generate unique +file names. This is a valid point; nevertheless, temporary files remain +more difficult than two-way pipes. + + (2) This is very different from the same operator in the C shell and in Bash. @@ -18578,15 +19417,15 @@ File: gawk.info, Node: TCP/IP Networking, Next: Profiling, Prev: Two-way I/O, unless the host that isn't close is busy hung or dead. - In addition to being able to open a two-way pipeline to a coprocess -on the same system (*note Two-way I/O::), it is possible to make a -two-way connection to another process on another system across an IP -network connection. +In addition to being able to open a two-way pipeline to a coprocess on +the same system (*note Two-way I/O::), it is possible to make a two-way +connection to another process on another system across an IP network +connection. You can think of this as just a _very long_ two-way pipeline to a coprocess. The way `gawk' decides that you want to use TCP/IP networking is by recognizing special file names that begin with one of -`/inet/', `/inet4/' or `/inet6'. +`/inet/', `/inet4/' or `/inet6/'. The full syntax of the special file name is `/NET-TYPE/PROTOCOL/LOCAL-PORT/REMOTE-HOST/REMOTE-PORT'. The @@ -18644,7 +19483,7 @@ much more complete introduction and discussion, as well as extensive examples. -File: gawk.info, Node: Profiling, Prev: TCP/IP Networking, Up: Advanced Features +File: gawk.info, Node: Profiling, Next: Advanced Features Summary, Prev: TCP/IP Networking, Up: Advanced Features 12.5 Profiling Your `awk' Programs ================================== @@ -18840,7 +19679,7 @@ As usual, the profiled version of the program is written to `awkprof.out', or to a different file if one specified with the `--profile' option. - Along with the regular profile, as shown earlier, the profile + Along with the regular profile, as shown earlier, the profile file includes a trace of any active functions: # Function Call Stack: @@ -18869,8 +19708,50 @@ by the `Ctrl-<\>' key. called this way, `gawk' "pretty prints" the program into `awkprof.out', without any execution counts. - NOTE: The `--pretty-print' option still runs your program. This - will change in the next major release. + NOTE: Once upon a time, the `--pretty-print' option would also run + your program. This is is no longer the case. + + +File: gawk.info, Node: Advanced Features Summary, Prev: Profiling, Up: Advanced Features + +12.6 Summary +============ + + * The `--non-decimal-data' option causes `gawk' to treat octal- and + hexadecimal-looking input data as octal and hexadecimal. This + option should be used with caution or not at all; use of + `strtonum()' is preferable. + + * You can take over complete control of sorting in `for (INDX in + ARRAY)' array traversal by setting `PROCINFO["sorted_in"]' to the + name of a user-defined function that does the comparison of array + elements based on index and value. + + * Similarly, you can supply the name of a user-defined comparison + function as the third argument to either `asort()' or `asorti()' + to control how those functions sort arrays. Or you may provide one + of the predefined control strings that work for + `PROCINFO["sorted_in"]'. + + * You can use the `|&' operator to create a two-way pipe to a + co-process. You read from the co-process with `getline' and write + to it with `print' or `printf'. Use `close()' to close off the + co-process completely, or optionally, close off one side of the + two-way communications. + + * By using special "file names" with the `|&' operator, you can open + a TCP/IP (or UDP/IP) connection to remote hosts in the Internet. + `gawk' supports both IPv4 an IPv6. + + * You can generate statement count profiles of your program. This + can help you determine which parts of your program may be taking + the most time and let you tune them more easily. Sending the + `USR1' signal while profiling causes `gawk' to dump the profile + and keep going, including a function call stack. + + * You can also just "pretty print" the program. This currently also + runs the program, but that will change in the next major release. + File: gawk.info, Node: Internationalization, Next: Debugger, Prev: Advanced Features, Up: Top @@ -18902,6 +19783,7 @@ requirement. * Translator i18n:: Features for the translator. * I18N Example:: A simple i18n example. * Gawk I18N:: `gawk' is also internationalized. +* I18N Summary:: Summary of I18N stuff. File: gawk.info, Node: I18N and L10N, Next: Explaining gettext, Up: Internationalization @@ -18924,6 +19806,7 @@ File: gawk.info, Node: Explaining gettext, Next: Programmer i18n, Prev: I18N 13.2 GNU `gettext' ================== +`gawk' uses GNU `gettext' to provide its internationalization features. The facilities in GNU `gettext' focus on messages; strings printed by a program, either directly or via formatting with `printf' or `sprintf()'.(1) @@ -19017,9 +19900,9 @@ are: `LC_CTYPE' Character-type information (alphabetic, digit, upper- or - lowercase, and so on). This information is accessed via the POSIX - character classes in regular expressions, such as `/[[:alnum:]]/' - (*note Regexp Operators::). + lowercase, and so on) as well as character encoding. This + information is accessed via the POSIX character classes in regular + expressions, such as `/[[:alnum:]]/' (*note Regexp Operators::). `LC_MONETARY' Monetary information, such as the currency symbol, and whether the @@ -19029,10 +19912,6 @@ are: Numeric information, such as which characters to use for the decimal point and the thousands separator.(2) -`LC_RESPONSE' - Response information, such as how "yes" and "no" appear in the - local language, and possibly other information as well. - `LC_TIME' Time- and date-related information, such as 12- or 24-hour clock, month printed before or after the day in a date, local month @@ -19070,7 +19949,7 @@ internationalization: for translation at runtime. String constants without a leading underscore are not translated. -`dcgettext(STRING [, DOMAIN [, CATEGORY]])' +``dcgettext(STRING' [`,' DOMAIN [`,' CATEGORY]]`)'' Return the translation of STRING in text domain DOMAIN for locale category CATEGORY. The default value for DOMAIN is the current value of `TEXTDOMAIN'. The default value for CATEGORY is @@ -19087,7 +19966,7 @@ internationalization: be simple and to allow for reasonable `awk'-style default arguments. -`dcngettext(STRING1, STRING2, NUMBER [, DOMAIN [, CATEGORY]])' +``dcngettext(STRING1, STRING2, NUMBER' [`,' DOMAIN [`,' CATEGORY]]`)'' Return the plural form used for NUMBER of the translation of STRING1 and STRING2 in text domain DOMAIN for locale category CATEGORY. STRING1 is the English singular variant of a message, @@ -19098,7 +19977,7 @@ internationalization: The same remarks about argument order as for the `dcgettext()' function apply. -`bindtextdomain(DIRECTORY [, DOMAIN])' +``bindtextdomain(DIRECTORY' [`,' DOMAIN ]`)'' Change the directory in which `gettext' looks for `.gmo' files, in case they will not or cannot be placed in the standard locations (e.g., during testing). Return the directory in which DOMAIN is @@ -19129,16 +20008,27 @@ outlined in *note Explaining gettext::, like so: printf(_"Number of users is %d\n", nusers) 3. If you are creating strings dynamically, you can still translate - them, using the `dcgettext()' built-in function: + them, using the `dcgettext()' built-in function:(1) - message = nusers " users logged in" - message = dcgettext(message, "adminprog") - print message + if (groggy) + message = dcgettext("%d customers disturbing me\n", "adminprog") + else + message = dcgettext("enjoying %d customers\n", "adminprog") + printf(message, ncustomers) Here, the call to `dcgettext()' supplies a different text domain (`"adminprog"') in which to find the message, but it uses the default `"LC_MESSAGES"' category. + The previous example only works if `ncustomers' is greater than + one. This example would be better done with `dcngettext()': + + if (groggy) + message = dcngettext("%d customer disturbing me\n", "%d customers disturbing me\n", "adminprog") + else + message = dcngettext("enjoying %d customer\n", "enjoying %d customers\n", "adminprog") + printf(message, ncustomers) + 4. During development, you might want to put the `.gmo' file in a private directory for testing. This is done with the `bindtextdomain()' built-in function: @@ -19158,6 +20048,10 @@ outlined in *note Explaining gettext::, like so: *Note I18N Example::, for an example program showing the steps to create and use translations from `awk'. + ---------- Footnotes ---------- + + (1) Thanks to Bruno Haible for this example. + File: gawk.info, Node: Translator i18n, Next: I18N Example, Prev: Programmer i18n, Up: Internationalization @@ -19197,8 +20091,11 @@ Instead, it parses it as usual and prints all marked strings to standard output in the format of a GNU `gettext' Portable Object file. Also included in the output are any constant strings that appear as the first argument to `dcgettext()' or as the first and second argument to -`dcngettext()'.(1) *Note I18N Example::, for the full list of steps to -go through to create and test translations for `guide'. +`dcngettext()'.(1) You should distribute the generated `.pot' file with +your `awk' program; translators will eventually use it to provide you +translations that you can also then distribute. *Note I18N Example::, +for the full list of steps to go through to create and test +translations for `guide'. ---------- Footnotes ---------- @@ -19403,19 +20300,19 @@ Following are the translations: msgstr "Like, the scoop is" The next step is to make the directory to hold the binary message -object file and then to create the `guide.gmo' file. The directory +object file and then to create the `guide.mo' file. We pretend that +our file is to be used in the `en_US.UTF-8' locale. The directory layout shown here is standard for GNU `gettext' on GNU/Linux systems. Other versions of `gettext' may use a different layout: - $ mkdir en_US en_US/LC_MESSAGES + $ mkdir en_US.UTF-8 en_US.UTF-8/LC_MESSAGES The `msgfmt' utility does the conversion from human-readable `.po' -file to machine-readable `.gmo' file. By default, `msgfmt' creates a +file to machine-readable `.mo' file. By default, `msgfmt' creates a file named `messages'. This file must be renamed and placed in the proper directory so that `gawk' can find it: - $ msgfmt guide-mellow.po - $ mv messages en_US/LC_MESSAGES/guide.gmo + $ msgfmt guide-mellow.po -o en_US.UTF-8/LC_MESSAGES/guide.mo Finally, we run the program to test it: @@ -19438,7 +20335,7 @@ and `bindtextdomain()' (*note I18N Portability::) are in a file named (1) Perhaps it would be better if it were called "Hippy." Ah, well. -File: gawk.info, Node: Gawk I18N, Prev: I18N Example, Up: Internationalization +File: gawk.info, Node: Gawk I18N, Next: I18N Summary, Prev: I18N Example, Up: Internationalization 13.6 `gawk' Can Speak Your Language =================================== @@ -19446,13 +20343,46 @@ File: gawk.info, Node: Gawk I18N, Prev: I18N Example, Up: Internationalizatio `gawk' itself has been internationalized using the GNU `gettext' package. (GNU `gettext' is described in complete detail in *note (GNU `gettext' utilities)Top:: gettext, GNU gettext tools.) As of this -writing, the latest version of GNU `gettext' is version 0.18.2.1 -(ftp://ftp.gnu.org/gnu/gettext/gettext-0.18.2.1.tar.gz). +writing, the latest version of GNU `gettext' is version 0.19.1 +(ftp://ftp.gnu.org/gnu/gettext/gettext-0.19.1.tar.gz). If a translation of `gawk''s messages exists, then `gawk' produces usage messages, warnings, and fatal errors in the local language. +File: gawk.info, Node: I18N Summary, Prev: Gawk I18N, Up: Internationalization + +13.7 Summary +============ + + * Internationalization means writing a program such that it can use + multiple languages without requiring source-code changes. + Localization means providing the data necessary for an + internationalized program to work in a particular language. + + * `gawk' uses GNU `gettext' to let you internationalize and localize + `awk' programs. A program's text domain identifies the program + for grouping all messages and other data together. + + * You mark a program's strings for translation by preceding them with + an underscore. Once that is done, the strings are extracted into a + `.pot' file. This file is copied for each language into a `.po' + file, and the `.po' files are compiled into `.gmo' files for use + at runtime. + + * You can use position specifications with `sprintf()' and `printf' + to rearrange the placement of argument values in formatted strings + and output. This is useful for the translations of format control + strings. + + * The internationalization features have been designed so that they + can be easily worked around in a standard `awk'. + + * `gawk' itself has been internationalized and ships with a number + of translations for its messages. + + + File: gawk.info, Node: Debugger, Next: Arbitrary Precision Arithmetic, Prev: Internationalization, Up: Top 14 Debugging `awk' Programs @@ -19475,12 +20405,13 @@ program is easy. * List of Debugger Commands:: Main debugger commands. * Readline Support:: Readline support. * Limitations:: Limitations and future plans. +* Debugging Summary:: Debugging summary. File: gawk.info, Node: Debugging, Next: Sample Debugging Session, Up: Debugger -14.1 Introduction to `gawk' Debugger -==================================== +14.1 Introduction to The `gawk' Debugger +======================================== This minor node introduces debugging in general and begins the discussion of debugging in `gawk'. @@ -19635,7 +20566,7 @@ options. (`gawk' is not designed to debug command-line programs, only programs contained in files.) In our case, we invoke the debugger like this: - $ gawk -D -f getopt.awk -f join.awk -f uniq.awk inputfile + $ gawk -D -f getopt.awk -f join.awk -f uniq.awk -1 inputfile where both `getopt.awk' and `uniq.awk' are in `$AWKPATH'. (Experienced users of GDB or similar debuggers should note that this syntax is @@ -19687,7 +20618,7 @@ for a breakpoint in `uniq.awk' is at the beginning of the function To set the breakpoint, use the `b' (breakpoint) command: gawk> b are_equal - -| Breakpoint 1 set at file `awklib/eg/prog/uniq.awk', line 64 + -| Breakpoint 1 set at file `awklib/eg/prog/uniq.awk', line 63 The debugger tells us the file and line number where the breakpoint is. Now type `r' or `run' and the program runs until it hits the @@ -19697,8 +20628,8 @@ breakpoint for the first time: -| Starting program: -| Stopping in Rule ... -| Breakpoint 1, are_equal(n, m, clast, cline, alast, aline) - at `awklib/eg/prog/uniq.awk':64 - -| 64 if (fcount == 0 && charcount == 0) + at `awklib/eg/prog/uniq.awk':63 + -| 63 if (fcount == 0 && charcount == 0) gawk> Now we can look at what's going on inside our program. First of all, @@ -19708,11 +20639,11 @@ the current stack frames: gawk> bt -| #0 are_equal(n, m, clast, cline, alast, aline) - at `awklib/eg/prog/uniq.awk':69 - -| #1 in main() at `awklib/eg/prog/uniq.awk':89 + at `awklib/eg/prog/uniq.awk':68 + -| #1 in main() at `awklib/eg/prog/uniq.awk':88 This tells us that `are_equal()' was called by the main program at -line 89 of `uniq.awk'. (This is not a big surprise, since this is the +line 88 of `uniq.awk'. (This is not a big surprise, since this is the only call to `are_equal()' in the program, but in more complex programs, knowing who called a function and with what parameters can be the key to finding the source of the problem.) @@ -19731,13 +20662,13 @@ function was called without arguments (*note Function Calls::). A more useful variable to display might be the current record: gawk> p $0 - -| $0 = string ("gawk is a wonderful program!") + -| $0 = "gawk is a wonderful program!" This might be a bit puzzling at first since this is the second line of our test input above. Let's look at `NR': gawk> p NR - -| NR = number (2) + -| NR = 2 So we can see that `are_equal()' was only called for the second record of the file. Of course, this is because our program contains a rule for @@ -19751,7 +20682,7 @@ of the file. Of course, this is because our program contains a rule for OK, let's just check that that rule worked correctly: gawk> p last - -| last = string ("awk is a wonderful program!") + -| last = "awk is a wonderful program!" Everything we have done so far has verified that the program has worked as planned, up to and including the call to `are_equal()', so @@ -19760,42 +20691,39 @@ must begin "stepping through" the lines of `are_equal()'. We start by typing `n' (for "next"): gawk> n - -| 67 if (fcount > 0) { + -| 66 if (fcount > 0) { - This tells us that `gawk' is now ready to execute line 67, which + This tells us that `gawk' is now ready to execute line 66, which decides whether to give the lines the special "field skipping" treatment -indicated by the `-f' command-line option. (Notice that we skipped -from where we were before at line 64 to here, since the condition in -line 64 - - if (fcount == 0 && charcount == 0) - -was false.) +indicated by the `-1' command-line option. (Notice that we skipped +from where we were before at line 63 to here, since the condition in +line 63 `if (fcount == 0 && charcount == 0)' was false.) Continuing to step, we now get to the splitting of the current and last records: gawk> n - -| 68 n = split(last, alast) + -| 67 n = split(last, alast) gawk> n - -| 69 m = split($0, aline) + -| 68 m = split($0, aline) At this point, we should be curious to see what our records were split into, so we try to look: gawk> p n m alast aline - -| n = number (5) - -| m = number (5) + -| n = 5 + -| m = untyped variable -| alast = array, 5 elements - -| aline = array, 5 elements + -| aline = untyped variable (The `p' command can take more than one argument, similar to `awk''s `print' statement.) This is kind of disappointing, though. All we found out is that -there are five elements in each of our arrays. Useful enough (we now -know that none of the words were accidentally left out), but what if we -want to see inside the array? +there are five elements in `alast'; `m' and `aline' don't have values +yet since we are at line 68 but haven't executed it yet. This +information is useful enough (we now know that none of the words were +accidentally left out), but what if we want to see inside the array? The first choice would be to use subscripts: @@ -19805,25 +20733,25 @@ want to see inside the array? Oops! gawk> p alast[1] - -| alast["1"] = string ("awk") + -| alast["1"] = "awk" This would be kind of slow for a 100-member array, though, so `gawk' provides a shortcut (reminiscent of another language not to be mentioned): gawk> p @alast - -| alast["1"] = string ("awk") - -| alast["2"] = string ("is") - -| alast["3"] = string ("a") - -| alast["4"] = string ("wonderful") - -| alast["5"] = string ("program!") + -| alast["1"] = "awk" + -| alast["2"] = "is" + -| alast["3"] = "a" + -| alast["4"] = "wonderful" + -| alast["5"] = "program!" It looks like we got this far OK. Let's take another step or two: gawk> n - -| 70 clast = join(alast, fcount, n) + -| 69 clast = join(alast, fcount, n) gawk> n - -| 71 cline = join(aline, fcount, m) + -| 70 cline = join(aline, fcount, m) Well, here we are at our error (sorry to spoil the suspense). What we had in mind was to join the fields starting from the second one to @@ -19831,8 +20759,8 @@ make the virtual record to compare, and if the first field was numbered zero, this would work. Let's look at what we've got: gawk> p cline clast - -| cline = string ("gawk is a wonderful program!") - -| clast = string ("awk is a wonderful program!") + -| cline = "gawk is a wonderful program!" + -| clast = "awk is a wonderful program!" Hey, those look pretty familiar! They're just our original, unaltered, input records. A little thinking (the human brain is still @@ -19876,7 +20804,7 @@ following descriptions, commands which may be abbreviated show the abbreviation on a second description line. A debugger command name may also be truncated if that partial name is unambiguous. The debugger has the built-in capability to automatically repeat the previous command -when just hitting <Enter>. This works for the commands `list', `next', +just by hitting <Enter>. This works for the commands `list', `next', `nexti', `step', `stepi' and `continue' executed without any argument. * Menu: @@ -20136,7 +21064,7 @@ AWK STATEMENTS `set' VAR`='VALUE Assign a constant (number or string) value to an `awk' variable or field. String values must be enclosed between double quotes - (`"..."'). + (`"'...`"'). You can also set special `awk' variables, such as `FS', `NF', `NR', etc. @@ -20190,11 +21118,12 @@ are: `frame' [N] `f' [N] - Select and print (frame number, function and argument names, - source file, and the source line) stack frame N. Frame 0 is the - currently executing, or "innermost", frame (function call), frame - 1 is the frame that called the innermost one. The highest numbered - frame is the one for the main program. + Select and print stack frame N. Frame 0 is the currently + executing, or "innermost", frame (function call), frame 1 is the + frame that called the innermost one. The highest numbered frame is + the one for the main program. The printed information consists of + the frame number, function and argument names, source file, and + the source line. `up' [COUNT] Move COUNT (default 1) frames up the stack toward the outermost @@ -20279,16 +21208,16 @@ from a file. The commands are: `prompt' The debugger prompt. The default is `gawk> '. - `save_history [on | off]' + `save_history' [`on' | `off'] Save command history to file `./.gawk_history'. The default is `on'. - `save_options [on | off]' + `save_options' [`on' | `off'] Save current options to file `./.gawkrc' upon exit. The default is `on'. Options are read back in to the next session upon startup. - `trace [on | off]' + `trace' [`on' | `off'] Turn instruction tracing on or off. The default is `off'. `save' FILENAME @@ -20327,7 +21256,7 @@ categories, as follows: Program::) demonstrates: gawk> dump - -| # BEGIN + -| # BEGIN -| -| [ 1:0xfcd340] Op_rule : [in_rule = BEGIN] [source_file = brini.awk] -| [ 1:0xfcc240] Op_push_i : "~" [MALLOC|STRING|STRCUR] @@ -20417,7 +21346,7 @@ categories, as follows: accidentally type `q' or `quit', to make sure you really want to quit. -`trace' `on' | `off' +`trace' [`on' | `off'] Turn on or off a continuous printing of instructions which are about to be executed, along with printing the `awk' line which they implement. The default is `off'. @@ -20433,9 +21362,10 @@ File: gawk.info, Node: Readline Support, Next: Limitations, Prev: List of Deb 14.4 Readline Support ===================== -If `gawk' is compiled with the `readline' library, you can take -advantage of that library's command completion and history expansion -features. The following types of completion are available: +If `gawk' is compiled with the `readline' library +(http://cnswww.cns.cwru.edu/php/chet/readline/readline.html), you can +take advantage of that library's command completion and history +expansion features. The following types of completion are available: Command completion Command names. @@ -20455,7 +21385,7 @@ Variable name completion -File: gawk.info, Node: Limitations, Prev: Readline Support, Up: Debugger +File: gawk.info, Node: Limitations, Next: Debugging Summary, Prev: Readline Support, Up: Debugger 14.5 Limitations and Future Plans ================================= @@ -20470,19 +21400,18 @@ some limitations. A few which are worth being aware of are: what your mistake was, though, you'll feel like a real guru. * If you perused the dump of opcodes in *note Miscellaneous Debugger - Commands::, (or if you are already familiar with `gawk' internals), + Commands:: (or if you are already familiar with `gawk' internals), you will realize that much of the internal manipulation of data in `gawk', as in many interpreters, is done on a stack. `Op_push', `Op_pop', etc., are the "bread and butter" of most `gawk' code. - Unfortunately, as of now, the `gawk' debugger does not allow you - to examine the stack's contents. - That is, the intermediate results of expression evaluation are on - the stack, but cannot be printed. Rather, only variables which - are defined in the program can be printed. Of course, a - workaround for this is to use more explicit variables at the - debugging stage and then change back to obscure, perhaps more - optimal code later. + Unfortunately, as of now, the `gawk' debugger does not allow you + to examine the stack's contents. That is, the intermediate + results of expression evaluation are on the stack, but cannot be + printed. Rather, only variables which are defined in the program + can be printed. Of course, a workaround for this is to use more + explicit variables at the debugging stage and then change back to + obscure, perhaps more optimal code later. * There is no way to look "inside" the process of compiling regular expressions to see if you got it right. As an `awk' programmer, @@ -20503,362 +21432,336 @@ features may be added, and of course feel free to try to add them yourself! -File: gawk.info, Node: Arbitrary Precision Arithmetic, Next: Dynamic Extensions, Prev: Debugger, Up: Top +File: gawk.info, Node: Debugging Summary, Prev: Limitations, Up: Debugger -15 Arithmetic and Arbitrary Precision Arithmetic with `gawk' -************************************************************ +14.6 Summary +============ - There's a credibility gap: We don't know how much of the - computer's answers to believe. Novice computer users solve this - problem by implicitly trusting in the computer as an infallible - authority; they tend to believe that all digits of a printed - answer are significant. Disillusioned computer users have just the - opposite approach; they are constantly afraid that their answers - are almost meaningless.(1) -- Donald Knuth + * Programs rarely work correctly the first time. Finding bugs is + "debugging" and a program that helps you find bugs is a + "debugger". `gawk' has a built-in debugger that works very + similarly to the GNU Debugger, GDB. - This major node discusses issues that you may encounter when -performing arithmetic. It begins by discussing some of the general -attributes of computer arithmetic, along with how this can influence -what you see when running `awk' programs. This discussion applies to -all versions of `awk'. + * Debuggers let you step through your program one statement at a + time, examine and change variable and array values, and do a + number of other things that let you understand what your program + is actually doing (as opposed to what it is supposed to do). - The major node then moves on to describe "arbitrary precision -arithmetic", a feature which is specific to `gawk'. + * Like most debuggers, the `gawk' debugger works in terms of stack + frames, and lets you set both breakpoints (stop at a point in the + code) and watchpoints (stop when a data value changes). -* Menu: + * The debugger command set is fairly complete, providing control over + breakpoints, execution, viewing and changing data, working with + the stack, getting information, and other tasks. -* General Arithmetic:: An introduction to computer arithmetic. -* Floating-point Programming:: Effective Floating-point Programming. -* Gawk and MPFR:: How `gawk' provides - arbitrary-precision arithmetic. -* Arbitrary Precision Floats:: Arbitrary Precision Floating-point Arithmetic - with `gawk'. -* Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic with - `gawk'. + * If the `readline' library is available when `gawk' is compiled, it + is used by the debugger to provide command-line history and + editing. - ---------- Footnotes ---------- - - (1) Donald E. Knuth. `The Art of Computer Programming'. Volume 2, -`Seminumerical Algorithms', third edition, 1998, ISBN 0-201-89683-4, p. -229. -File: gawk.info, Node: General Arithmetic, Next: Floating-point Programming, Up: Arbitrary Precision Arithmetic +File: gawk.info, Node: Arbitrary Precision Arithmetic, Next: Dynamic Extensions, Prev: Debugger, Up: Top -15.1 A General Description of Computer Arithmetic -================================================= +15 Arithmetic and Arbitrary Precision Arithmetic with `gawk' +************************************************************ + +This major node introduces some basic concepts relating to how +computers do arithmetic and briefly lists the features in `gawk' for +performing arbitrary precision floating point computations. It then +proceeds to describe floating-point arithmetic, which is what `awk' +uses for all its computations, including a discussion of arbitrary +precision floating point arithmetic, which is a feature available only +in `gawk'. It continues on to present arbitrary precision integers, and +concludes with a description of some points where `gawk' and the POSIX +standard are not quite in agreement. -Within computers, there are two kinds of numeric values: "integers" and -"floating-point". In school, integer values were referred to as -"whole" numbers--that is, numbers without any fractional part, such as -1, 42, or -17. The advantage to integer numbers is that they represent -values exactly. The disadvantage is that their range is limited. On -most systems, this range is -2,147,483,648 to 2,147,483,647. However, -many systems now support a range from -9,223,372,036,854,775,808 to -9,223,372,036,854,775,807. - - Integer values come in two flavors: "signed" and "unsigned". Signed -values may be negative or positive, with the range of values just -described. Unsigned values are always positive. On most systems, the -range is from 0 to 4,294,967,295. However, many systems now support a -range from 0 to 18,446,744,073,709,551,615. - - Floating-point numbers represent what are called "real" numbers; -i.e., those that do have a fractional part, such as 3.1415927. The -advantage to floating-point numbers is that they can represent a much -larger range of values. The disadvantage is that there are numbers -that they cannot represent exactly. `awk' uses "double precision" -floating-point numbers, which can hold more digits than "single -precision" floating-point numbers. - - There a several important issues to be aware of, described next. + NOTE: Most users of `gawk' can safely skip this chapter. But if + you want to do scientific calculations with `gawk', this is the + place to be. * Menu: -* Floating Point Issues:: Stuff to know about floating-point numbers. -* Integer Programming:: Effective integer programming. +* Computer Arithmetic:: A quick intro to computer math. +* Math Definitions:: Defining terms used. +* MPFR features:: The MPFR features in `gawk'. +* FP Math Caution:: Things to know. +* Arbitrary Precision Integers:: Arbitrary Precision Integer Arithmetic with + `gawk'. +* POSIX Floating Point Problems:: Standards Versus Existing Practice. +* Floating point summary:: Summary of floating point discussion. -File: gawk.info, Node: Floating Point Issues, Next: Integer Programming, Up: General Arithmetic +File: gawk.info, Node: Computer Arithmetic, Next: Math Definitions, Up: Arbitrary Precision Arithmetic -15.1.1 Floating-Point Number Caveats ------------------------------------- - -This minor node describes some of the issues involved in using -floating-point numbers. +15.1 A General Description of Computer Arithmetic +================================================= - There is a very nice paper on floating-point arithmetic -(http://www.validlab.com/goldberg/paper.pdf) by David Goldberg, "What -Every Computer Scientist Should Know About Floating-point Arithmetic," -`ACM Computing Surveys' *23*, 1 (1991-03), 5-48. This is worth reading -if you are interested in the details, but it does require a background -in computer science. +Until now, we have worked with data as either numbers or strings. +Ultimately, however, computers represent everything in terms of "binary +digits", or "bits". A decimal digit can take on any of 10 values: zero +through nine. A binary digit can take on any of two values, zero or +one. Using binary, computers (and computer software) can represent and +manipulate numerical and character data. In general, the more bits you +can use to represent a particular thing, the greater the range of +possible values it can take on. + + Modern computers support at least two, and often more, ways to do +arithmetic. Each kind of arithmetic uses a different representation +(organization of the bits) for the numbers. The kinds of arithmetic +that interest us are: + +Decimal arithmetic + This is the kind of arithmetic you learned in elementary school, + using paper and pencil (and/or a calculator). In theory, numbers + can have an arbitrary number of digits on either side (or both + sides) of the decimal point, and the results of a computation are + always exact. + + Some modern system can do decimal arithmetic in hardware, but + usually you need a special software library to provide access to + these instructions. There are also libraries that do decimal + arithmetic entirely in software. + + Despite the fact that some users expect `gawk' to be performing + decimal arithmetic,(1) it does not do so. + +Integer arithmetic + In school, integer values were referred to as "whole" numbers--that + is, numbers without any fractional part, such as 1, 42, or -17. + The advantage to integer numbers is that they represent values + exactly. The disadvantage is that their range is limited. + + In computers, integer values come in two flavors: "signed" and + "unsigned". Signed values may be negative or positive, whereas + unsigned values are always positive (that is, greater than or equal + to zero). + + In computer systems, integer arithmetic is exact, but the possible + range of values is limited. Integer arithmetic is generally + faster than floating point arithmetic. + +Floating point arithmetic + Floating-point numbers represent what were called in school "real" + numbers; i.e., those that have a fractional part, such as + 3.1415927. The advantage to floating-point numbers is that they + can represent a much larger range of values than can integers. + The disadvantage is that there are numbers that they cannot + represent exactly. + + Modern systems support floating point arithmetic in hardware, with + a limited range of values. There are software libraries that allow + the use of arbitrary precision floating point calculations. + + POSIX `awk' uses "double precision" floating-point numbers, which + can hold more digits than "single precision" floating-point + numbers. `gawk' has facilities for performing arbitrary precision + floating point arithmetic, which we describe in more detail + shortly. + + Computers work with integer and floating point values of different +ranges. Integer values are usually either 32 or 64 bits in size. Single +precision floating point values occupy 32 bits, whereas double precision +floating point values occupy 64 bits. Floating point values are always +signed. The possible ranges of values are shown in the following table. + +Numeric representation Miniumum value Maximum value +--------------------------------------------------------------------------- +32-bit signed integer -2,147,483,648 2,147,483,647 +32-bit unsigned integer 0 4,294,967,295 +64-bit signed integer -9,223,372,036,854,775,8089,223,372,036,854,775,807 +64-bit unsigned integer 0 18,446,744,073,709,551,615 +Single precision `1.175494e-38' `3.402823e+38' +floating point +(approximate) +Double precision `2.225074e-308' `1.797693e+308' +floating point +(approximate) -* Menu: + ---------- Footnotes ---------- -* String Conversion Precision:: The String Value Can Lie. -* Unexpected Results:: Floating Point Numbers Are Not Abstract - Numbers. -* POSIX Floating Point Problems:: Standards Versus Existing Practice. + (1) We don't know why they expect this, but they do. -File: gawk.info, Node: String Conversion Precision, Next: Unexpected Results, Up: Floating Point Issues +File: gawk.info, Node: Math Definitions, Next: MPFR features, Prev: Computer Arithmetic, Up: Arbitrary Precision Arithmetic -15.1.1.1 The String Value Can Lie -................................. +15.2 Other Stuff To Know +======================== -Internally, `awk' keeps both the numeric value (double precision -floating-point) and the string value for a variable. Separately, `awk' -keeps track of what type the variable has (*note Typing and -Comparison::), which plays a role in how variables are used in -comparisons. +The rest of this major node uses a number of terms. Here are some +informal definitions that should help you work your way through the +material here. - It is important to note that the string value for a number may not -reflect the full value (all the digits) that the numeric value actually -contains. The following program, `values.awk', illustrates this: +"Accuracy" + A floating-point calculation's accuracy is how close it comes to + the real (paper and pencil) value. - { - sum = $1 + $2 - # see it for what it is - printf("sum = %.12g\n", sum) - # use CONVFMT - a = "<" sum ">" - print "a =", a - # use OFMT - print "sum =", sum - } +"Error" + The difference between what the result of a computation "should be" + and what it actually is. It is best to minimize error as much as + possible. -This program shows the full value of the sum of `$1' and `$2' using -`printf', and then prints the string values obtained from both -automatic conversion (via `CONVFMT') and from printing (via `OFMT'). +"Exponent" + The order of magnitude of a value; some number of bits in a + floating-point value store the exponent. - Here is what happens when the program is run: +"Inf" + A special value representing infinity. Operations involving another + number and infinity produce infinity. - $ echo 3.654321 1.2345678 | awk -f values.awk - -| sum = 4.8888888 - -| a = <4.88889> - -| sum = 4.88889 +"NaN" + "Not A Number."(1). A special value that results from attempting a + calculation that has no answer as a real number. In such a case, + programs can either receive a floating-point exception, or get + `NaN' back as the result. The IEEE 754 standard recommends that + systems return `NaN'. Some examples: - This makes it clear that the full numeric value is different from -what the default string representations show. + `sqrt(-1)' + This makes sense in the range of complex numbers, but not in + the range of real numbers, so the result is `NaN'. - `CONVFMT''s default value is `"%.6g"', which yields a value with at -most six significant digits. For some applications, you might want to -change it to specify more precision. On most modern machines, most of -the time, 17 digits is enough to capture a floating-point number's -value exactly.(1) + `log(-8)' + -8 is out of the domain of `log()', so the result is `NaN'. - ---------- Footnotes ---------- +"Normalized" + How the significand (see later in this list) is usually stored. The + value is adjusted so that the first bit is one, and then that + leading one is assumed instead of physically stored. This + provides one extra bit of precision. - (1) Pathological cases can require up to 752 digits (!), but we -doubt that you need to worry about this. +"Precision" + The number of bits used to represent a floating-point number. The + more bits, the more digits you can represent. Binary and decimal + precisions are related approximately, according to the formula: - -File: gawk.info, Node: Unexpected Results, Next: POSIX Floating Point Problems, Prev: String Conversion Precision, Up: Floating Point Issues + PREC = 3.322 * DPS -15.1.1.2 Floating Point Numbers Are Not Abstract Numbers -........................................................ + Here, PREC denotes the binary precision (measured in bits) and DPS + (short for decimal places) is the decimal digits. -Unlike numbers in the abstract sense (such as what you studied in high -school or college arithmetic), numbers stored in computers are limited -in certain ways. They cannot represent an infinite number of digits, -nor can they always represent things exactly. In particular, -floating-point numbers cannot always represent values exactly. Here is -an example: +"Rounding mode" + How numbers are rounded up or down when necessary. More details + are provided later. - $ awk '{ printf("%010d\n", $1 * 100) }' - 515.79 - -| 0000051579 - 515.80 - -| 0000051579 - 515.81 - -| 0000051580 - 515.82 - -| 0000051582 - Ctrl-d +"Significand" + A floating point value consists the significand multiplied by 10 + to the power of the exponent. For example, in `1.2345e67', the + significand is `1.2345'. -This shows that some values can be represented exactly, whereas others -are only approximated. This is not a "bug" in `awk', but simply an -artifact of how computers represent numbers. +"Stability" + From the Wikipedia article on numerical stability + (http://en.wikipedia.org/wiki/Numerical_stability): "Calculations + that can be proven not to magnify approximation errors are called + "numerically stable"." - NOTE: It cannot be emphasized enough that the behavior just - described is fundamental to modern computers. You will see this - kind of thing happen in _any_ programming language using hardware - floating-point numbers. It is _not_ a bug in `gawk', nor is it - something that can be "just fixed." + See the Wikipedia article on accuracy and precision +(http://en.wikipedia.org/wiki/Accuracy_and_precision) for more +information on some of those terms. - Another peculiarity of floating-point numbers on modern systems is -that they often have more than one representation for the number zero! -In particular, it is possible to represent "minus zero" as well as -regular, or "positive" zero. + On modern systems, floating-point hardware uses the representation +and operations defined by the IEEE 754 standard. Three of the standard +IEEE 754 types are 32-bit single precision, 64-bit double precision and +128-bit quadruple precision. The standard also specifies extended +precision formats to allow greater precisions and larger exponent +ranges. (`awk' uses only the 64-bit double precision format.) - This example shows that negative and positive zero are distinct -values when stored internally, but that they are in fact equal to each -other, as well as to "regular" zero: - - $ gawk 'BEGIN { mz = -0 ; pz = 0 - > printf "-0 = %g, +0 = %g, (-0 == +0) -> %d\n", mz, pz, mz == pz - > printf "mz == 0 -> %d, pz == 0 -> %d\n", mz == 0, pz == 0 - > }' - -| -0 = -0, +0 = 0, (-0 == +0) -> 1 - -| mz == 0 -> 1, pz == 0 -> 1 + *note table-ieee-formats:: lists the precision and exponent field +values for the basic IEEE 754 binary formats: - It helps to keep this in mind should you process numeric data that -contains negative zero values; the fact that the zero is negative is -noted and can affect comparisons. +Name Total bits Precision emin emax +--------------------------------------------------------------------------- +Single 32 24 -126 +127 +Double 64 53 -1022 +1023 +Quadruple 128 113 -16382 +16383 - -File: gawk.info, Node: POSIX Floating Point Problems, Prev: Unexpected Results, Up: Floating Point Issues +Table 15.1: Basic IEEE Format Context Values -15.1.1.3 Standards Versus Existing Practice -........................................... + NOTE: The precision numbers include the implied leading one that + gives them one extra bit of significand. -Historically, `awk' has converted any non-numeric looking string to the -numeric value zero, when required. Furthermore, the original -definition of the language and the original POSIX standards specified -that `awk' only understands decimal numbers (base 10), and not octal -(base 8) or hexadecimal numbers (base 16). + ---------- Footnotes ---------- - Changes in the language of the 2001 and 2004 POSIX standards can be -interpreted to imply that `awk' should support additional features. -These features are: + (1) Thanks to Michael Brennan for this description, which I have +paraphrased, and for the examples - * Interpretation of floating point data values specified in - hexadecimal notation (`0xDEADBEEF'). (Note: data values, _not_ - source code constants.) + +File: gawk.info, Node: MPFR features, Next: FP Math Caution, Prev: Math Definitions, Up: Arbitrary Precision Arithmetic - * Support for the special IEEE 754 floating point values "Not A - Number" (NaN), positive Infinity ("inf") and negative Infinity - ("-inf"). In particular, the format for these values is as - specified by the ISO 1999 C standard, which ignores case and can - allow machine-dependent additional characters after the `nan' and - allow either `inf' or `infinity'. +15.3 Arbitrary Precison Arithmetic Features In `gawk' +===================================================== - The first problem is that both of these are clear changes to -historical practice: +By default, `gawk' uses the double precision floating point values +supplied by the hardware of the system it runs on. However, if it was +compiled to do, `gawk' uses the GNU MPFR (http://www.mpfr.org) and GNU +MP (http://gmplib.org) (GMP) libraries for arbitrary precision +arithmetic on numbers. You can see if MPFR support is available like +so: - * The `gawk' maintainer feels that supporting hexadecimal floating - point values, in particular, is ugly, and was never intended by the - original designers to be part of the language. + $ gawk --version + -| GNU Awk 4.1.1, API: 1.1 (GNU MPFR 3.1.0-p3, GNU MP 5.0.2) + -| Copyright (C) 1989, 1991-2014 Free Software Foundation. + ... - * Allowing completely alphabetic strings to have valid numeric - values is also a very severe departure from historical practice. +(You may see different version numbers than what's shown here. That's +OK; what's important is to see that GNU MPFR and GNU MP are listed in +the output.) - The second problem is that the `gawk' maintainer feels that this -interpretation of the standard, which requires a certain amount of -"language lawyering" to arrive at in the first place, was not even -intended by the standard developers. In other words, "we see how you -got where you are, but we don't think that that's where you want to be." + Additionally, there are a few elements available in the `PROCINFO' +array to provide information about the MPFR and GMP libraries (*note +Auto-set::). + + The MPFR library provides precise control over precisions and +rounding modes, and gives correctly rounded, reproducible, +platform-independent results. With the `-M' command-line option, all +floating-point arithmetic operators and numeric functions can yield +results to any desired precision level supported by MPFR. + + Two built-in variables, `PREC' and `ROUNDMODE', provide control over +the working precision and the rounding mode. The precision and the +rounding mode are set globally for every operation to follow. *Note +Auto-set::, for more information. - Recognizing the above issues, but attempting to provide compatibility -with the earlier versions of the standard, the 2008 POSIX standard -added explicit wording to allow, but not require, that `awk' support -hexadecimal floating point values and special values for "Not A Number" -and infinity. + +File: gawk.info, Node: FP Math Caution, Next: Arbitrary Precision Integers, Prev: MPFR features, Up: Arbitrary Precision Arithmetic - Although the `gawk' maintainer continues to feel that providing -those features is inadvisable, nevertheless, on systems that support -IEEE floating point, it seems reasonable to provide _some_ way to -support NaN and Infinity values. The solution implemented in `gawk' is -as follows: +15.4 Floating Point Arithmetic: Caveat Emptor! +============================================== - * With the `--posix' command-line option, `gawk' becomes "hands - off." String values are passed directly to the system library's - `strtod()' function, and if it successfully returns a numeric - value, that is what's used.(1) By definition, the results are not - portable across different systems. They are also a little - surprising: + Math class is tough! -- Teen Talk Barbie, July 1992 - $ echo nanny | gawk --posix '{ print $1 + 0 }' - -| nan - $ echo 0xDeadBeef | gawk --posix '{ print $1 + 0 }' - -| 3735928559 + This minor node provides a high level overview of the issues +involved when doing lots of floating-point arithmetic.(1) The +discussion applies to both hardware and arbitrary-precision +floating-point arithmetic. - * Without `--posix', `gawk' interprets the four strings `+inf', - `-inf', `+nan', and `-nan' specially, producing the corresponding - special numeric values. The leading sign acts a signal to `gawk' - (and the user) that the value is really numeric. Hexadecimal - floating point is not supported (unless you also use - `--non-decimal-data', which is _not_ recommended). For example: + CAUTION: The material here is purposely general. If you need to do + serious computer arithmetic, you should do some research first, + and not rely just on what we tell you. - $ echo nanny | gawk '{ print $1 + 0 }' - -| 0 - $ echo +nan | gawk '{ print $1 + 0 }' - -| nan - $ echo 0xDeadBeef | gawk '{ print $1 + 0 }' - -| 0 +* Menu: - `gawk' does ignore case in the four special values. Thus `+nan' - and `+NaN' are the same. +* Inexactness of computations:: Floating point math is not exact. +* Getting Accuracy:: Getting more accuracy takes some work. +* Try To Round:: Add digits and round. +* Setting precision:: How to set the precision. +* Setting the rounding mode:: How to set the rounding mode. ---------- Footnotes ---------- - (1) You asked for it, you got it. + (1) There is a very nice paper on floating-point arithmetic +(http://www.validlab.com/goldberg/paper.pdf) by David Goldberg, "What +Every Computer Scientist Should Know About Floating-point Arithmetic," +`ACM Computing Surveys' *23*, 1 (1991-03), 5-48. This is worth reading +if you are interested in the details, but it does require a background +in computer science. -File: gawk.info, Node: Integer Programming, Prev: Floating Point Issues, Up: General Arithmetic - -15.1.2 Mixing Integers And Floating-point ------------------------------------------ +File: gawk.info, Node: Inexactness of computations, Next: Getting Accuracy, Up: FP Math Caution -As has been mentioned already, `awk' uses hardware double precision -with 64-bit IEEE binary floating-point representation for numbers on -most systems. A large integer like 9,007,199,254,740,997 has a binary -representation that, although finite, is more than 53 bits long; it -must also be rounded to 53 bits. The biggest integer that can be -stored in a C `double' is usually the same as the largest possible -value of a `double'. If your system `double' is an IEEE 64-bit -`double', this largest possible value is an integer and can be -represented precisely. What more should one know about integers? - - If you want to know what is the largest integer, such that it and -all smaller integers can be stored in 64-bit doubles without losing -precision, then the answer is 2^53. The next representable number is -the even number 2^53 + 2, meaning it is unlikely that you will be able -to make `gawk' print 2^53 + 1 in integer format. The range of integers -exactly representable by a 64-bit double is [-2^53, 2^53]. If you ever -see an integer outside this range in `awk' using 64-bit doubles, you -have reason to be very suspicious about the accuracy of the output. -Here is a simple program with erroneous output: - - $ gawk 'BEGIN { i = 2^53 - 1; for (j = 0; j < 4; j++) print i + j }' - -| 9007199254740991 - -| 9007199254740992 - -| 9007199254740992 - -| 9007199254740994 - - The lesson is to not assume that any large integer printed by `awk' -represents an exact result from your computation, especially if it wraps -around on your screen. - - -File: gawk.info, Node: Floating-point Programming, Next: Gawk and MPFR, Prev: General Arithmetic, Up: Arbitrary Precision Arithmetic - -15.2 Understanding Floating-point Programming -============================================= +15.4.1 Floating Point Arithmetic Is Not Exact +--------------------------------------------- -Numerical programming is an extensive area; if you need to develop -sophisticated numerical algorithms then `gawk' may not be the ideal -tool, and this documentation may not be sufficient. It might require -digesting a book or two(1) to really internalize how to compute with -ideal accuracy and precision, and the result often depends on the -particular application. - - NOTE: A floating-point calculation's "accuracy" is how close it - comes to the real value. This is as opposed to the "precision", - which usually refers to the number of bits used to represent the - number (see the Wikipedia article - (http://en.wikipedia.org/wiki/Accuracy_and_precision) for more - information). - - There are two options for doing floating-point calculations: -hardware floating-point (as used by standard `awk' and the default for -`gawk'), and "arbitrary-precision" floating-point, which is software -based. From this point forward, this major node aims to provide enough -information to understand both, and then will focus on `gawk''s -facilities for the latter.(2) - - Binary floating-point representations and arithmetic are inexact. +Binary floating-point representations and arithmetic are inexact. Simple values like 0.1 cannot be precisely represented using binary floating-point numbers, and the limited precision of floating-point numbers means that slight changes in the order of operations or the @@ -20867,9 +21770,21 @@ matters worse, with arbitrary precision floating-point, you can set the precision before starting a computation, but then you cannot be sure of the number of significant decimal places in the final result. - Sometimes, before you start to write any code, you should think more -about what you really want and what's really happening. Consider the -two numbers in the following example: +* Menu: + +* Inexact representation:: Numbers are not exactly represented. +* Comparing FP Values:: How to compare floating point values. +* Errors accumulate:: Errors get bigger as they go. + + +File: gawk.info, Node: Inexact representation, Next: Comparing FP Values, Up: Inexactness of computations + +15.4.1.1 Many Numbers Cannot Be Represented Exactly +................................................... + +So, before you start to write any code, you should think about what you +really want and what's really happening. Consider the two numbers in +the following example: x = 0.875 # 1/2 + 1/4 + 1/8 y = 0.425 @@ -20892,20 +21807,44 @@ you can always specify how much precision you would like in your output. Usually this is a format string like `"%.15g"', which when used in the previous example, produces an output identical to the input. - Because the underlying representation can be a little bit off from -the exact value, comparing floating-point values to see if they are -equal is generally not a good idea. Here is an example where it does -not work like you expect: + +File: gawk.info, Node: Comparing FP Values, Next: Errors accumulate, Prev: Inexact representation, Up: Inexactness of computations + +15.4.1.2 Be Careful Comparing Values +.................................... + +Because the underlying representation can be a little bit off from the +exact value, comparing floating-point values to see if they are exactly +equal is generally a bad idea. Here is an example where it does not +work like you would expect: $ gawk 'BEGIN { print (0.1 + 12.2 == 12.3) }' -| 0 - The loss of accuracy during a single computation with floating-point + The general wisdom when comparing floating-point values is to see if +they are within some small range of each other (called a "delta", or +"tolerance"). You have to decide how small a delta is important to +you. Code to do this looks something like this: + + delta = 0.00001 # for example + difference = abs(a) - abs(b) # subtract the two values + if (difference < delta) + # all ok + else + # not ok + + +File: gawk.info, Node: Errors accumulate, Prev: Comparing FP Values, Up: Inexactness of computations + +15.4.1.3 Errors Accumulate +.......................... + +The loss of accuracy during a single computation with floating-point numbers usually isn't enough to worry about. However, if you compute a value which is the result of a sequence of floating point operations, the error can accumulate and greatly affect the computation itself. -Here is an attempt to compute the value of the constant pi using one of -its many series representations: +Here is an attempt to compute the value of pi using one of its many +series representations: BEGIN { x = 1.0 / sqrt(3.0) @@ -20917,9 +21856,9 @@ its many series representations: } } - When run, the early errors propagating through later computations -cause the loop to terminate prematurely after an attempt to divide by -zero. + When run, the early errors propagate through later computations, +causing the loop to terminate prematurely after attempting to divide by +zero: $ gawk -f pi.awk -| 3.215390309173475 @@ -20942,166 +21881,176 @@ representations yield an unexpected result: > }' -| 4 - Can computation using arbitrary precision help with the previous -examples? If you are impatient to know, see *note Exact Arithmetic::. + +File: gawk.info, Node: Getting Accuracy, Next: Try To Round, Prev: Inexactness of computations, Up: FP Math Caution - Instead of arbitrary precision floating-point arithmetic, often all -you need is an adjustment of your logic or a different order for the -operations in your calculation. The stability and the accuracy of the -computation of the constant pi in the earlier example can be enhanced -by using the following simple algebraic transformation: +15.4.2 Getting The Accuracy You Need +------------------------------------ - (sqrt(x * x + 1) - 1) / x = x / (sqrt(x * x + 1) + 1) +Can arbitrary precision arithmetic give exact results? There are no +easy answers. The standard rules of algebra often do not apply when +using floating-point arithmetic. Among other things, the distributive +and associative laws do not hold completely, and order of operation may +be important for your computation. Rounding error, cumulative precision +loss and underflow are often troublesome. -After making this, change the program does converge to pi in under 30 -iterations: + When `gawk' tests the expressions `0.1 + 12.2' and `12.3' for +equality using the machine double precision arithmetic, it decides that +they are not equal! (*Note Comparing FP Values::.) You can get the +result you want by increasing the precision; 56 bits in this case does +the job: - $ gawk -f pi2.awk - -| 3.215390309173473 - -| 3.159659942097501 - -| 3.146086215131436 - -| 3.142714599645370 - -| 3.141873049979825 - ... - -| 3.141592653589797 - -| 3.141592653589797 + $ gawk -M -v PREC=56 'BEGIN { print (0.1 + 12.2 == 12.3) }' + -| 1 - There is no need to be unduly suspicious about the results from -floating-point arithmetic. The lesson to remember is that -floating-point arithmetic is always more complex than arithmetic using -pencil and paper. In order to take advantage of the power of computer -floating-point, you need to know its limitations and work within them. -For most casual use of floating-point arithmetic, you will often get -the expected result in the end if you simply round the display of your -final results to the correct number of significant decimal digits. + If adding more bits is good, perhaps adding even more bits of +precision is better? Here is what happens if we use an even larger +value of `PREC': - As general advice, avoid presenting numerical data in a manner that -implies better precision than is actually the case. + $ gawk -M -v PREC=201 'BEGIN { print (0.1 + 12.2 == 12.3) }' + -| 0 -* Menu: + This is not a bug in `gawk' or in the MPFR library. It is easy to +forget that the finite number of bits used to store the value is often +just an approximation after proper rounding. The test for equality +succeeds if and only if _all_ bits in the two operands are exactly the +same. Since this is not necessarily true after floating-point +computations with a particular precision and effective rounding rule, a +straight test for equality may not work. Instead, compare the two +numbers to see if they are within the desirable delta of each other. -* Floating-point Representation:: Binary floating-point representation. -* Floating-point Context:: Floating-point context. -* Rounding Mode:: Floating-point rounding mode. + In applications where 15 or fewer decimal places suffice, hardware +double precision arithmetic can be adequate, and is usually much faster. +But you need to keep in mind that every floating-point operation can +suffer a new rounding error with catastrophic consequences as +illustrated by our earlier attempt to compute the value of pi. Extra +precision can greatly enhance the stability and the accuracy of your +computation in such cases. - ---------- Footnotes ---------- + Repeated addition is not necessarily equivalent to multiplication in +floating-point arithmetic. In the example in *note Errors accumulate::: - (1) One recommended title is `Numerical Computing with IEEE Floating -Point Arithmetic', Michael L. Overton, Society for Industrial and -Applied Mathematics, 2004. ISBN: 0-89871-482-6, ISBN-13: -978-0-89871-482-1. See `http://www.cs.nyu.edu/cs/faculty/overton/book'. + $ gawk 'BEGIN { + > for (d = 1.1; d <= 1.5; d += 0.1) # loop five times (?) + > i++ + > print i + > }' + -| 4 - (2) If you are interested in other tools that perform arbitrary -precision arithmetic, you may want to investigate the POSIX `bc' tool. -See the POSIX specification for it -(http://pubs.opengroup.org/onlinepubs/009695399/utilities/bc.html), for -more information. +you may or may not succeed in getting the correct result by choosing an +arbitrarily large value for `PREC'. Reformulation of the problem at +hand is often the correct approach in such situations. -File: gawk.info, Node: Floating-point Representation, Next: Floating-point Context, Up: Floating-point Programming - -15.2.1 Binary Floating-point Representation -------------------------------------------- - -Although floating-point representations vary from machine to machine, -the most commonly encountered representation is that defined by the -IEEE 754 Standard. An IEEE-754 format value has three components: +File: gawk.info, Node: Try To Round, Next: Setting precision, Prev: Getting Accuracy, Up: FP Math Caution - * A sign bit telling whether the number is positive or negative. +15.4.3 Try A Few Extra Bits of Precision and Rounding +----------------------------------------------------- - * An "exponent", E, giving its order of magnitude. +Instead of arbitrary precision floating-point arithmetic, often all you +need is an adjustment of your logic or a different order for the +operations in your calculation. The stability and the accuracy of the +computation of pi in the earlier example can be enhanced by using the +following simple algebraic transformation: - * A "significand", S, specifying the actual digits of the number. + (sqrt(x * x + 1) - 1) / x == x / (sqrt(x * x + 1) + 1) - The value of the number is then S * 2^E. The first bit of a -non-zero binary significand is always one, so the significand in an -IEEE-754 format only includes the fractional part, leaving the leading -one implicit. The significand is stored in "normalized" format, which -means that the first bit is always a one. +After making this, change the program converges to pi in under 30 +iterations: - Three of the standard IEEE-754 types are 32-bit single precision, -64-bit double precision and 128-bit quadruple precision. The standard -also specifies extended precision formats to allow greater precisions -and larger exponent ranges. + $ gawk -f pi2.awk + -| 3.215390309173473 + -| 3.159659942097501 + -| 3.146086215131436 + -| 3.142714599645370 + -| 3.141873049979825 + ... + -| 3.141592653589797 + -| 3.141592653589797 -File: gawk.info, Node: Floating-point Context, Next: Rounding Mode, Prev: Floating-point Representation, Up: Floating-point Programming - -15.2.2 Floating-point Context ------------------------------ - -A floating-point "context" defines the environment for arithmetic -operations. It governs precision, sets rules for rounding, and limits -the range for exponents. The context has the following primary -components: - -"Precision" - Precision of the floating-point format in bits. - -"emax" - Maximum exponent allowed for the format. - -"emin" - Minimum exponent allowed for the format. +File: gawk.info, Node: Setting precision, Next: Setting the rounding mode, Prev: Try To Round, Up: FP Math Caution -"Underflow behavior" - The format may or may not support gradual underflow. - -"Rounding" - The rounding mode of the context. +15.4.4 Setting The Precision +---------------------------- - *note table-ieee-formats:: lists the precision and exponent field -values for the basic IEEE-754 binary formats: +`gawk' uses a global working precision; it does not keep track of the +precision or accuracy of individual numbers. Performing an arithmetic +operation or calling a built-in function rounds the result to the +current working precision. The default working precision is 53 bits, +which you can modify using the built-in variable `PREC'. You can also +set the value to one of the predefined case-insensitive strings shown +in *note table-predefined-precision-strings::, to emulate an IEEE 754 +binary format. -Name Total bits Precision emin emax ---------------------------------------------------------------------------- -Single 32 24 -126 +127 -Double 64 53 -1022 +1023 -Quadruple 128 113 -16382 +16383 +`PREC' IEEE 754 Binary Format +--------------------------------------------------- +`"half"' 16-bit half-precision. +`"single"' Basic 32-bit single precision. +`"double"' Basic 64-bit double precision. +`"quad"' Basic 128-bit quadruple precision. +`"oct"' 256-bit octuple precision. -Table 15.1: Basic IEEE Format Context Values +Table 15.2: Predefined Precision Strings For `PREC' - NOTE: The precision numbers include the implied leading one that - gives them one extra bit of significand. + The following example illustrates the effects of changing precision +on arithmetic operations: - A floating-point context can also determine which signals are treated -as exceptions, and can set rules for arithmetic with special values. -Please consult the IEEE-754 standard or other resources for details. + $ gawk -M -v PREC=100 'BEGIN { x = 1.0e-400; print x + 0 + > PREC = "double"; print x + 0 }' + -| 1e-400 + -| 0 - `gawk' ordinarily uses the hardware double precision representation -for numbers. On most systems, this is IEEE-754 floating-point format, -corresponding to 64-bit binary with 53 bits of precision. + CAUTION: Be wary of floating-point constants! When reading a + floating-point constant from program source code, `gawk' uses the + default precision (that of a C `double'), unless overridden by an + assignment to the special variable `PREC' on the command line, to + store it internally as a MPFR number. Changing the precision + using `PREC' in the program text does _not_ change the precision + of a constant. + + If you need to represent a floating-point constant at a higher + precision than the default and cannot use a command-line + assignment to `PREC', you should either specify the constant as a + string, or as a rational number, whenever possible. The following + example illustrates the differences among various ways to print a + floating-point constant: - NOTE: In case an underflow occurs, the standard allows, but does - not require, the result from an arithmetic operation to be a - number smaller than the smallest nonzero normalized number. Such - numbers do not have as many significant digits as normal numbers, - and are called "denormals" or "subnormals". The alternative, - simply returning a zero, is called "flush to zero". The basic - IEEE-754 binary formats support subnormal numbers. + $ gawk -M 'BEGIN { PREC = 113; printf("%0.25f\n", 0.1) }' + -| 0.1000000000000000055511151 + $ gawk -M -v PREC=113 'BEGIN { printf("%0.25f\n", 0.1) }' + -| 0.1000000000000000000000000 + $ gawk -M 'BEGIN { PREC = 113; printf("%0.25f\n", "0.1") }' + -| 0.1000000000000000000000000 + $ gawk -M 'BEGIN { PREC = 113; printf("%0.25f\n", 1/10) }' + -| 0.1000000000000000000000000 -File: gawk.info, Node: Rounding Mode, Prev: Floating-point Context, Up: Floating-point Programming +File: gawk.info, Node: Setting the rounding mode, Prev: Setting precision, Up: FP Math Caution -15.2.3 Floating-point Rounding Mode ------------------------------------ +15.4.5 Setting The Rounding Mode +-------------------------------- -The "rounding mode" specifies the behavior for the results of numerical -operations when discarding extra precision. Each rounding mode indicates -how the least significant returned digit of a rounded result is to be -calculated. *note table-rounding-modes:: lists the IEEE-754 defined -rounding modes: +The `ROUNDMODE' variable provides program level control over the +rounding mode. The correspondence between `ROUNDMODE' and the IEEE +rounding modes is shown in *note table-gawk-rounding-modes::. -Rounding Mode IEEE Name --------------------------------------------------------------------------- -Round to nearest, ties to even `roundTiesToEven' -Round toward plus Infinity `roundTowardPositive' -Round toward negative Infinity `roundTowardNegative' -Round toward zero `roundTowardZero' -Round to nearest, ties away `roundTiesToAway' -from zero +Rounding Mode IEEE Name `ROUNDMODE' +--------------------------------------------------------------------------- +Round to nearest, ties to even `roundTiesToEven' `"N"' or `"n"' +Round toward plus Infinity `roundTowardPositive' `"U"' or `"u"' +Round toward negative Infinity `roundTowardNegative' `"D"' or `"d"' +Round toward zero `roundTowardZero' `"Z"' or `"z"' +Round to nearest, ties away `roundTiesToAway' `"A"' or `"a"' +from zero + +Table 15.3: `gawk' Rounding Modes -Table 15.2: IEEE 754 Rounding Modes + `ROUNDMODE' has the default value `"N"', which selects the IEEE 754 +rounding mode `roundTiesToEven'. In *note Table 15.3: +table-gawk-rounding-modes, the value `"A"' selects `roundTiesToAway'. +This is only available if your version of the MPFR library supports it; +otherwise setting `ROUNDMODE' to `"A"' has no effect. The default mode `roundTiesToEven' is the most preferred, but the least intuitive. This method does the obvious thing for most values, by @@ -21136,20 +22085,19 @@ produces the following output when run on the author's system:(1) 3.5 => 4 4.5 => 4 - The theory behind the rounding mode `roundTiesToEven' is that it -more or less evenly distributes upward and downward rounds of exact -halves, which might cause any round-off error to cancel itself out. -This is the default rounding mode used in IEEE-754 computing functions -and operators. + The theory behind `roundTiesToEven' is that it more or less evenly +distributes upward and downward rounds of exact halves, which might +cause any accumulating round-off error to cancel itself out. This is the +default rounding mode for IEEE 754 computing functions and operators. The other rounding modes are rarely used. Round toward positive infinity (`roundTowardPositive') and round toward negative infinity -(`roundTowardNegative') are often used to implement interval arithmetic, -where you adjust the rounding mode to calculate upper and lower bounds -for the range of output. The `roundTowardZero' mode can be used for -converting floating-point numbers to integers. The rounding mode -`roundTiesToAway' rounds the result to the nearest number and selects -the number with the larger magnitude if a tie occurs. +(`roundTowardNegative') are often used to implement interval +arithmetic, where you adjust the rounding mode to calculate upper and +lower bounds for the range of output. The `roundTowardZero' mode can be +used for converting floating-point numbers to integers. The rounding +mode `roundTiesToAway' rounds the result to the nearest number and +selects the number with the larger magnitude if a tie occurs. Some numerical analysts will tell you that your choice of rounding style has tremendous impact on the final outcome, and advise you to @@ -21158,418 +22106,255 @@ round-off error problems by setting the precision initially to some value sufficiently larger than the final desired precision, so that the accumulation of round-off error does not influence the outcome. If you suspect that results from your computation are sensitive to -accumulation of round-off error, one way to be sure is to look for a -significant difference in output when you change the rounding mode. +accumulation of round-off error, look for a significant difference in +output when you change the rounding mode to be sure. ---------- Footnotes ---------- (1) It is possible for the output to be completely different if the -C library in your system does not use the IEEE-754 even-rounding rule +C library in your system does not use the IEEE 754 even-rounding rule to round halfway cases for `printf'. -File: gawk.info, Node: Gawk and MPFR, Next: Arbitrary Precision Floats, Prev: Floating-point Programming, Up: Arbitrary Precision Arithmetic +File: gawk.info, Node: Arbitrary Precision Integers, Next: POSIX Floating Point Problems, Prev: FP Math Caution, Up: Arbitrary Precision Arithmetic -15.3 `gawk' + MPFR = Powerful Arithmetic -======================================== - -The rest of this major node describes how to use the arbitrary precision -(also known as "multiple precision" or "infinite precision") numeric -capabilities in `gawk' to produce maximally accurate results when you -need it. +15.5 Arbitrary Precision Integer Arithmetic with `gawk' +======================================================= - But first you should check if your version of `gawk' supports -arbitrary precision arithmetic. The easiest way to find out is to look -at the output of the following command: +When given the `-M' option, `gawk' performs all integer arithmetic +using GMP arbitrary precision integers. Any number that looks like an +integer in a source or data file is stored as an arbitrary precision +integer. The size of the integer is limited only by the available +memory. For example, the following computes 5^4^3^2, the result of +which is beyond the limits of ordinary hardware double-precision +floating point values: - $ ./gawk --version - -| GNU Awk 4.1.1, API: 1.1 (GNU MPFR 3.1.0-p3, GNU MP 5.0.2) - -| Copyright (C) 1989, 1991-2014 Free Software Foundation. - ... + $ gawk -M 'BEGIN { + > x = 5^4^3^2 + > print "# of digits =", length(x) + > print substr(x, 1, 20), "...", substr(x, length(x) - 19, 20) + > }' + -| # of digits = 183231 + -| 62060698786608744707 ... 92256259918212890625 -(You may see different version numbers than what's shown here. That's -OK; what's important is to see that GNU MPFR and GNU MP are listed in -the output.) + If instead you were to compute the same value using arbitrary +precision floating-point values, the precision needed for correct +output (using the formula `prec = 3.322 * dps'), would be 3.322 x +183231, or 608693. - `gawk' uses the GNU MPFR (http://www.mpfr.org) and GNU MP -(http://gmplib.org) (GMP) libraries for arbitrary precision arithmetic -on numbers. So if you do not see the names of these libraries in the -output, then your version of `gawk' does not support arbitrary -precision arithmetic. + The result from an arithmetic operation with an integer and a +floating-point value is a floating-point value with a precision equal +to the working precision. The following program calculates the eighth +term in Sylvester's sequence(1) using a recurrence: - Additionally, there are a few elements available in the `PROCINFO' -array to provide information about the MPFR and GMP libraries. *Note -Auto-set::, for more information. + $ gawk -M 'BEGIN { + > s = 2.0 + > for (i = 1; i <= 7; i++) + > s = s * (s - 1) + 1 + > print s + > }' + -| 113423713055421845118910464 - -File: gawk.info, Node: Arbitrary Precision Floats, Next: Arbitrary Precision Integers, Prev: Gawk and MPFR, Up: Arbitrary Precision Arithmetic - -15.4 Arbitrary Precision Floating-point Arithmetic with `gawk' -============================================================== - -`gawk' uses the GNU MPFR library for arbitrary precision floating-point -arithmetic. The MPFR library provides precise control over precisions -and rounding modes, and gives correctly rounded, reproducible, -platform-independent results. With one of the command-line options -`--bignum' or `-M', all floating-point arithmetic operators and numeric -functions can yield results to any desired precision level supported by -MPFR. Two built-in variables, `PREC' and `ROUNDMODE', provide control -over the working precision and the rounding mode (*note Setting -Precision::, and *note Setting Rounding Mode::). The precision and the -rounding mode are set globally for every operation to follow. - - The default working precision for arbitrary precision floating-point -values is 53 bits, and the default value for `ROUNDMODE' is `"N"', -which selects the IEEE-754 `roundTiesToEven' rounding mode (*note -Rounding Mode::).(1) `gawk' uses the default exponent range in MPFR -(EMAX = 2^30 - 1, EMIN = -EMAX) for all floating-point contexts. There -is no explicit mechanism to adjust the exponent range. MPFR does not -implement subnormal numbers by default, and this behavior cannot be -changed in `gawk'. - - NOTE: When emulating an IEEE-754 format (*note Setting - Precision::), `gawk' internally adjusts the exponent range to the - value defined for the format and also performs computations needed - for gradual underflow (subnormal numbers). - - NOTE: MPFR numbers are variable-size entities, consuming only as - much space as needed to store the significant digits. Since the - performance using MPFR numbers pales in comparison to doing - arithmetic using the underlying machine types, you should consider - using only as much precision as needed by your program. + The output differs from the actual number, +113,423,713,055,421,844,361,000,443, because the default precision of +53 bits is not enough to represent the floating-point results exactly. +You can either increase the precision (100 bits is enough in this +case), or replace the floating-point constant `2.0' with an integer, to +perform all computations using integer arithmetic to get the correct +output. -* Menu: + Sometimes `gawk' must implicitly convert an arbitrary precision +integer into an arbitrary precision floating-point value. This is +primarily because the MPFR library does not always provide the relevant +interface to process arbitrary precision integers or mixed-mode numbers +as needed by an operation or function. In such a case, the precision is +set to the minimum value necessary for exact conversion, and the working +precision is not used for this purpose. If this is not what you need or +want, you can employ a subterfuge, and convert the integer to floating +point first, like this: -* Setting Precision:: Setting the working precision. -* Setting Rounding Mode:: Setting the rounding mode. -* Floating-point Constants:: Representing floating-point constants. -* Changing Precision:: Changing the precision of a number. -* Exact Arithmetic:: Exact arithmetic with floating-point numbers. + gawk -M 'BEGIN { n = 13; print (n + 0.0) % 2.0 }' - ---------- Footnotes ---------- + You can avoid this issue altogether by specifying the number as a +floating-point value to begin with: - (1) The default precision is 53 bits, since according to the MPFR -documentation, the library should be able to exactly reproduce all -computations with double-precision machine floating-point numbers -(`double' type in C), except the default exponent range is much wider -and subnormal numbers are not implemented. + gawk -M 'BEGIN { n = 13.0; print n % 2.0 }' - -File: gawk.info, Node: Setting Precision, Next: Setting Rounding Mode, Up: Arbitrary Precision Floats + Note that for the particular example above, it is likely best to +just use the following: -15.4.1 Setting the Working Precision ------------------------------------- + gawk -M 'BEGIN { n = 13; print n % 2 }' -`gawk' uses a global working precision; it does not keep track of the -precision or accuracy of individual numbers. Performing an arithmetic -operation or calling a built-in function rounds the result to the -current working precision. The default working precision is 53 bits, -which can be modified using the built-in variable `PREC'. You can also -set the value to one of the pre-defined case-insensitive strings shown -in *note table-predefined-precision-strings::, to emulate an IEEE-754 -binary format. + When dividing two arbitrary precision integers with either `/' or +`%', the result is typically an arbitrary precision floating point +value (unless the denominator evenly divides into the numerator). In +order to do integer division or remainder with arbitrary precision +integers, use the built-in `div()' function (*note Numeric Functions::). -`PREC' IEEE-754 Binary Format ---------------------------------------------------- -`"half"' 16-bit half-precision. -`"single"' Basic 32-bit single precision. -`"double"' Basic 64-bit double precision. -`"quad"' Basic 128-bit quadruple precision. -`"oct"' 256-bit octuple precision. + You can simulate the `div()' function in standard `awk' using this +user-defined function: -Table 15.3: Predefined precision strings for `PREC' + # div --- do integer division - The following example illustrates the effects of changing precision -on arithmetic operations: + function div(numerator, denominator, result, i) + { + split("", result) - $ gawk -M -v PREC=100 'BEGIN { x = 1.0e-400; print x + 0 - > PREC = "double"; print x + 0 }' - -| 1e-400 - -| 0 + numerator = int(numerator) + denominator = int(denominator) + result["quotient"] = int(numerator / denominator) + result["remainder"] = int(numerator % denominator) - Binary and decimal precisions are related approximately, according -to the formula: - - PREC = 3.322 * DPS - -Here, PREC denotes the binary precision (measured in bits) and DPS -(short for decimal places) is the decimal digits. We can easily -calculate how many decimal digits the 53-bit significand of an IEEE -double is equivalent to: 53 / 3.322 which is equal to about 15.95. But -what does 15.95 digits actually mean? It depends whether you are -concerned about how many digits you can rely on, or how many digits you -need. - - It is important to know how many bits it takes to uniquely identify -a double-precision value (the C type `double'). If you want to convert -from `double' to decimal and back to `double' (e.g., saving a `double' -representing an intermediate result to a file, and later reading it -back to restart the computation), then a few more decimal digits are -required. 17 digits is generally enough for a `double'. - - It can also be important to know what decimal numbers can be uniquely -represented with a `double'. If you want to convert from decimal to -`double' and back again, 15 digits is the most that you can get. Stated -differently, you should not present the numbers from your -floating-point computations with more than 15 significant digits in -them. + return 0.0 + } - Conversely, it takes a precision of 332 bits to hold an approximation -of the constant pi that is accurate to 100 decimal places. + ---------- Footnotes ---------- - You should always add some extra bits in order to avoid the -confusing round-off issues that occur because numbers are stored -internally in binary. + (1) Weisstein, Eric W. `Sylvester's Sequence'. From MathWorld--A +Wolfram Web Resource +(`http://mathworld.wolfram.com/SylvestersSequence.html'). -File: gawk.info, Node: Setting Rounding Mode, Next: Floating-point Constants, Prev: Setting Precision, Up: Arbitrary Precision Floats +File: gawk.info, Node: POSIX Floating Point Problems, Next: Floating point summary, Prev: Arbitrary Precision Integers, Up: Arbitrary Precision Arithmetic -15.4.2 Setting the Rounding Mode --------------------------------- - -The `ROUNDMODE' variable provides program level control over the -rounding mode. The correspondence between `ROUNDMODE' and the IEEE -rounding modes is shown in *note table-gawk-rounding-modes::. +15.6 Standards Versus Existing Practice +======================================= -Rounding Mode IEEE Name `ROUNDMODE' ---------------------------------------------------------------------------- -Round to nearest, ties to even `roundTiesToEven' `"N"' or `"n"' -Round toward plus Infinity `roundTowardPositive' `"U"' or `"u"' -Round toward negative Infinity `roundTowardNegative' `"D"' or `"d"' -Round toward zero `roundTowardZero' `"Z"' or `"z"' -Round to nearest, ties away `roundTiesToAway' `"A"' or `"a"' -from zero +Historically, `awk' has converted any non-numeric looking string to the +numeric value zero, when required. Furthermore, the original +definition of the language and the original POSIX standards specified +that `awk' only understands decimal numbers (base 10), and not octal +(base 8) or hexadecimal numbers (base 16). -Table 15.4: `gawk' Rounding Modes + Changes in the language of the 2001 and 2004 POSIX standards can be +interpreted to imply that `awk' should support additional features. +These features are: - `ROUNDMODE' has the default value `"N"', which selects the IEEE-754 -rounding mode `roundTiesToEven'. In *note Table 15.4: -table-gawk-rounding-modes, `"A"' is listed to select the IEEE-754 mode -`roundTiesToAway'. This is only available if your version of the MPFR -library supports it; otherwise setting `ROUNDMODE' to this value has no -effect. *Note Rounding Mode::, for the meanings of the various rounding -modes. + * Interpretation of floating point data values specified in + hexadecimal notation (e.g., `0xDEADBEEF'). (Note: data values, + _not_ source code constants.) - Here is an example of how to change the default rounding behavior of -`printf''s output: + * Support for the special IEEE 754 floating point values "Not A + Number" (NaN), positive Infinity ("inf") and negative Infinity + ("-inf"). In particular, the format for these values is as + specified by the ISO 1999 C standard, which ignores case and can + allow implementation-dependent additional characters after the + `nan' and allow either `inf' or `infinity'. - $ gawk -M -v ROUNDMODE="Z" 'BEGIN { printf("%.2f\n", 1.378) }' - -| 1.37 + The first problem is that both of these are clear changes to +historical practice: - -File: gawk.info, Node: Floating-point Constants, Next: Changing Precision, Prev: Setting Rounding Mode, Up: Arbitrary Precision Floats + * The `gawk' maintainer feels that supporting hexadecimal floating + point values, in particular, is ugly, and was never intended by the + original designers to be part of the language. -15.4.3 Representing Floating-point Constants --------------------------------------------- + * Allowing completely alphabetic strings to have valid numeric + values is also a very severe departure from historical practice. -Be wary of floating-point constants! When reading a floating-point -constant from program source code, `gawk' uses the default precision, -unless overridden by an assignment to the special variable `PREC' on -the command line, to store it internally as a MPFR number. Changing -the precision using `PREC' in the program text does _not_ change the -precision of a constant. If you need to represent a floating-point -constant at a higher precision than the default and cannot use a -command line assignment to `PREC', you should either specify the -constant as a string, or as a rational number, whenever possible. The -following example illustrates the differences among various ways to -print a floating-point constant: + The second problem is that the `gawk' maintainer feels that this +interpretation of the standard, which requires a certain amount of +"language lawyering" to arrive at in the first place, was not even +intended by the standard developers. In other words, "we see how you +got where you are, but we don't think that that's where you want to be." - $ gawk -M 'BEGIN { PREC = 113; printf("%0.25f\n", 0.1) }' - -| 0.1000000000000000055511151 - $ gawk -M -v PREC=113 'BEGIN { printf("%0.25f\n", 0.1) }' - -| 0.1000000000000000000000000 - $ gawk -M 'BEGIN { PREC = 113; printf("%0.25f\n", "0.1") }' - -| 0.1000000000000000000000000 - $ gawk -M 'BEGIN { PREC = 113; printf("%0.25f\n", 1/10) }' - -| 0.1000000000000000000000000 + Recognizing the above issues, but attempting to provide compatibility +with the earlier versions of the standard, the 2008 POSIX standard +added explicit wording to allow, but not require, that `awk' support +hexadecimal floating point values and special values for "Not A Number" +and infinity. - In the first case, the number is stored with the default precision -of 53 bits. + Although the `gawk' maintainer continues to feel that providing +those features is inadvisable, nevertheless, on systems that support +IEEE floating point, it seems reasonable to provide _some_ way to +support NaN and Infinity values. The solution implemented in `gawk' is +as follows: - -File: gawk.info, Node: Changing Precision, Next: Exact Arithmetic, Prev: Floating-point Constants, Up: Arbitrary Precision Floats + * With the `--posix' command-line option, `gawk' becomes "hands + off." String values are passed directly to the system library's + `strtod()' function, and if it successfully returns a numeric + value, that is what's used.(1) By definition, the results are not + portable across different systems. They are also a little + surprising: -15.4.4 Changing the Precision of a Number ------------------------------------------ + $ echo nanny | gawk --posix '{ print $1 + 0 }' + -| nan + $ echo 0xDeadBeef | gawk --posix '{ print $1 + 0 }' + -| 3735928559 - The point is that in any variable-precision package, a decision is - made on how to treat numbers given as data, or arising in - intermediate results, which are represented in floating-point - format to a precision lower than working precision. Do we promote - them to full membership of the high-precision club, or do we treat - them and all their associates as second-class citizens? Sometimes - the first course is proper, sometimes the second, and it takes - careful analysis to tell which.(1) -- Dirk Laurie - - `gawk' does not implicitly modify the precision of any previously -computed results when the working precision is changed with an -assignment to `PREC'. The precision of a number is always the one that -was used at the time of its creation, and there is no way for the user -to explicitly change it afterwards. However, since the result of a -floating-point arithmetic operation is always an arbitrary precision -floating-point value--with a precision set by the value of `PREC'--one -of the following workarounds effectively accomplishes the desired -behavior: - - x = x + 0.0 + * Without `--posix', `gawk' interprets the four strings `+inf', + `-inf', `+nan', and `-nan' specially, producing the corresponding + special numeric values. The leading sign acts a signal to `gawk' + (and the user) that the value is really numeric. Hexadecimal + floating point is not supported (unless you also use + `--non-decimal-data', which is _not_ recommended). For example: -or: + $ echo nanny | gawk '{ print $1 + 0 }' + -| 0 + $ echo +nan | gawk '{ print $1 + 0 }' + -| nan + $ echo 0xDeadBeef | gawk '{ print $1 + 0 }' + -| 0 - x += 0.0 + `gawk' ignores case in the four special values. Thus `+nan' and + `+NaN' are the same. ---------- Footnotes ---------- - (1) Dirk Laurie. `Variable-precision Arithmetic Considered Perilous --- A Detective Story'. Electronic Transactions on Numerical Analysis. -Volume 28, pp. 168-173, 2008. - - -File: gawk.info, Node: Exact Arithmetic, Prev: Changing Precision, Up: Arbitrary Precision Floats - -15.4.5 Exact Arithmetic with Floating-point Numbers ---------------------------------------------------- - - CAUTION: Never depend on the exactness of floating-point - arithmetic, even for apparently simple expressions! - - Can arbitrary precision arithmetic give exact results? There are no -easy answers. The standard rules of algebra often do not apply when -using floating-point arithmetic. Among other things, the distributive -and associative laws do not hold completely, and order of operation may -be important for your computation. Rounding error, cumulative precision -loss and underflow are often troublesome. - - When `gawk' tests the expressions `0.1 + 12.2' and `12.3' for -equality using the machine double precision arithmetic, it decides that -they are not equal! (*Note Floating-point Programming::.) You can get -the result you want by increasing the precision; 56 bits in this case -will get the job done: - - $ gawk -M -v PREC=56 'BEGIN { print (0.1 + 12.2 == 12.3) }' - -| 1 - - If adding more bits is good, perhaps adding even more bits of -precision is better? Here is what happens if we use an even larger -value of `PREC': - - $ gawk -M -v PREC=201 'BEGIN { print (0.1 + 12.2 == 12.3) }' - -| 0 - - This is not a bug in `gawk' or in the MPFR library. It is easy to -forget that the finite number of bits used to store the value is often -just an approximation after proper rounding. The test for equality -succeeds if and only if _all_ bits in the two operands are exactly the -same. Since this is not necessarily true after floating-point -computations with a particular precision and effective rounding rule, a -straight test for equality may not work. - - So, don't assume that floating-point values can be compared for -equality. You should also exercise caution when using other forms of -comparisons. The standard way to compare between floating-point -numbers is to determine how much error (or "tolerance") you will allow -in a comparison and check to see if one value is within this error -range of the other. - - In applications where 15 or fewer decimal places suffice, hardware -double precision arithmetic can be adequate, and is usually much faster. -But you do need to keep in mind that every floating-point operation can -suffer a new rounding error with catastrophic consequences as -illustrated by our earlier attempt to compute the value of the constant -pi (*note Floating-point Programming::). Extra precision can greatly -enhance the stability and the accuracy of your computation in such -cases. - - Repeated addition is not necessarily equivalent to multiplication in -floating-point arithmetic. In the example in *note Floating-point -Programming::: - - $ gawk 'BEGIN { - > for (d = 1.1; d <= 1.5; d += 0.1) # loop five times (?) - > i++ - > print i - > }' - -| 4 - -you may or may not succeed in getting the correct result by choosing an -arbitrarily large value for `PREC'. Reformulation of the problem at -hand is often the correct approach in such situations. + (1) You asked for it, you got it. -File: gawk.info, Node: Arbitrary Precision Integers, Prev: Arbitrary Precision Floats, Up: Arbitrary Precision Arithmetic +File: gawk.info, Node: Floating point summary, Prev: POSIX Floating Point Problems, Up: Arbitrary Precision Arithmetic -15.5 Arbitrary Precision Integer Arithmetic with `gawk' -======================================================= +15.7 Summary +============ -If one of the options `--bignum' or `-M' is specified, `gawk' performs -all integer arithmetic using GMP arbitrary precision integers. Any -number that looks like an integer in a program source or data file is -stored as an arbitrary precision integer. The size of the integer is -limited only by your computer's memory. The current floating-point -context has no effect on operations involving integers. For example, -the following computes 5^4^3^2, the result of which is beyond the -limits of ordinary `gawk' numbers: + * Most computer arithmetic is done using either integers or + floating-point values. The default for `awk' is to use + double-precision floating-point values. - $ gawk -M 'BEGIN { - > x = 5^4^3^2 - > print "# of digits =", length(x) - > print substr(x, 1, 20), "...", substr(x, length(x) - 19, 20) - > }' - -| # of digits = 183231 - -| 62060698786608744707 ... 92256259918212890625 + * In the early 1990's, Barbie mistakenly said "Math class is tough!" + While math isn't tough, floating-point arithmetic isn't the same + as pencil and paper math, and care must be taken: - If you were to compute the same value using arbitrary precision -floating-point values instead, the precision needed for correct output -(using the formula `prec = 3.322 * dps'), would be 3.322 x 183231, or -608693. + - Not all numbers can be represented exactly. - The result from an arithmetic operation with an integer and a -floating-point value is a floating-point value with a precision equal -to the working precision. The following program calculates the eighth -term in Sylvester's sequence(1) using a recurrence: + - Comparing values should use a delta, instead of being done + directly with `==' and `!='. - $ gawk -M 'BEGIN { - > s = 2.0 - > for (i = 1; i <= 7; i++) - > s = s * (s - 1) + 1 - > print s - > }' - -| 113423713055421845118910464 + - Errors accumulate. - The output differs from the actual number, -113,423,713,055,421,844,361,000,443, because the default precision of -53 bits is not enough to represent the floating-point results exactly. -You can either increase the precision (100 bits is enough in this -case), or replace the floating-point constant `2.0' with an integer, to -perform all computations using integer arithmetic to get the correct -output. + - Operations are not always truly associative or distributive. - It will sometimes be necessary for `gawk' to implicitly convert an -arbitrary precision integer into an arbitrary precision floating-point -value. This is primarily because the MPFR library does not always -provide the relevant interface to process arbitrary precision integers -or mixed-mode numbers as needed by an operation or function. In such a -case, the precision is set to the minimum value necessary for exact -conversion, and the working precision is not used for this purpose. If -this is not what you need or want, you can employ a subterfuge like -this: + * Increasing the accuracy can help, but it is not a panacea. - gawk -M 'BEGIN { n = 13; print (n + 0.0) % 2.0 }' + * Often, increasing the accuracy and then rounding to the desired + number of digits produces reasonable results. - You can avoid this issue altogether by specifying the number as a -floating-point value to begin with: + * Use `-M' (or `--bignum') to enable MPFR arithmetic. Use `PREC' to + set the precision in bits, and `ROUNDMODE' to set the IEEE 754 + rounding mode. - gawk -M 'BEGIN { n = 13.0; print n % 2.0 }' + * With `-M', `gawk' performs arbitrary precision integer arithmetic + using the GMP library. This is faster and more space efficient + than using MPFR for the same calculations. - Note that for the particular example above, it is likely best to -just use the following: + * There are several "dark corners" with respect to floating-point + numbers where `gawk' disagrees with the POSIX standard. It pays + to be aware of them. - gawk -M 'BEGIN { n = 13; print n % 2 }' + * Overall, there is no need to be unduly suspicious about the + results from floating-point arithmetic. The lesson to remember is + that floating-point arithmetic is always more complex than + arithmetic using pencil and paper. In order to take advantage of + the power of computer floating-point, you need to know its + limitations and work within them. For most casual use of + floating-point arithmetic, you will often get the expected result + if you simply round the display of your final results to the + correct number of significant decimal digits. - ---------- Footnotes ---------- + * As general advice, avoid presenting numerical data in a manner that + implies better precision than is actually the case. - (1) Weisstein, Eric W. `Sylvester's Sequence'. From MathWorld--A -Wolfram Web Resource. -`http://mathworld.wolfram.com/SylvestersSequence.html' File: gawk.info, Node: Dynamic Extensions, Next: Language History, Prev: Arbitrary Precision Arithmetic, Up: Top @@ -21602,6 +22387,8 @@ sample extensions are automatically built and installed when `gawk' is. * Extension Samples:: The sample extensions that ship with `gawk'. * gawkextlib:: The `gawkextlib' project. +* Extension summary:: Extension summary. +* Extension Exercises:: Exercises. File: gawk.info, Node: Extension Intro, Next: Plugin License, Up: Dynamic Extensions @@ -21655,7 +22442,8 @@ File: gawk.info, Node: Extension Mechanism Outline, Next: Extension API Descri Communication between `gawk' and an extension is two-way. First, when an extension is loaded, it is passed a pointer to a `struct' whose -fields are function pointers. This is shown in *note load-extension::. +fields are function pointers. This is shown in *note +figure-load-extension::. API Struct @@ -21687,7 +22475,7 @@ Figure 16.1: Loading The Extension function pointers, at runtime, without needing (link-time) access to `gawk''s symbols. One of these function pointers is to a function for "registering" new built-in functions. This is shown in *note -load-new-function::. +figure-load-new-function::. register_ext_func({ "chdir", do_chdir, 1 }); @@ -21707,7 +22495,7 @@ Figure 16.2: Loading The New Function with `gawk' by passing function pointers to the functions that provide the new feature (`do_chdir()', for example). `gawk' associates the function pointer with a name and can then call it, using a defined -calling convention. This is shown in *note call-new-function::. +calling convention. This is shown in *note figure-call-new-function::. BEGIN { chdir("/path") (*fnptr)(1); @@ -21728,9 +22516,9 @@ Figure 16.3: Calling The New Function the API `struct' to do its work, such as updating variables or arrays, printing messages, setting `ERRNO', and so on. - Convenience macros in the `gawkapi.h' header file make calling -through the function pointers look like regular function calls so that -extension code is quite readable and understandable. + Convenience macros make calling through the function pointers look +like regular function calls so that extension code is quite readable +and understandable. Although all of this sounds somewhat complicated, the result is that extension code is quite straightforward to write and to read. You can @@ -21740,7 +22528,7 @@ Example::) and also the `testext.c' code for testing the APIs. Some other bits and pieces: * The API provides access to `gawk''s `do_XXX' values, reflecting - command line options, like `do_lint', `do_profiling' and so on + command-line options, like `do_lint', `do_profiling' and so on (*note Extension API Variables::). These are informational: an extension cannot affect their values inside `gawk'. In addition, attempting to assign to them produces a compile-time error. @@ -21757,7 +22545,10 @@ File: gawk.info, Node: Extension API Description, Next: Finding Extensions, P 16.4 API Description ==================== -This (rather large) minor node describes the API in detail. +C or C++ code for an extension must include the header file +`gawkapi.h', which declares the functions and defines the data types +used to communicate with `gawk'. This (rather large) minor node +describes the API in detail. * Menu: @@ -21789,7 +22580,7 @@ through function pointers passed into your extension. API function pointers are provided for the following kinds of operations: - * Registrations functions. You may register: + * Registration functions. You may register: - extension functions, - exit callbacks, @@ -21841,6 +22632,7 @@ operations: C Entity Header File ------------------------------------------- `EOF' `<stdio.h>' + Values for `errno' `<errno.h>' `FILE' `<stdio.h>' `NULL' `<stddef.h>' `memcpy()' `<string.h>' @@ -21855,9 +22647,6 @@ operations: a portability hodge-podge as can be seen in some parts of the `gawk' source code. - To pass reasonable integer values for `ERRNO', you will also need - to include `<errno.h>'. - * The `gawkapi.h' file may be included more than once without ill effect. Doing so, however, is poor coding practice. @@ -21867,7 +22656,7 @@ operations: place `-Dinline=''' on your command line, or use the GNU Autotools and include a `config.h' file in your extensions. - * All pointers filled in by `gawk' are to memory managed by `gawk' + * All pointers filled in by `gawk' point to memory managed by `gawk' and should be treated by the extension as read-only. Memory for _all_ strings passed into `gawk' from the extension _must_ come from calling the API-provided function pointers `api_malloc()', @@ -21877,7 +22666,7 @@ operations: * The API defines several simple `struct's that map values as seen from `awk'. A value can be a `double', a string, or an array (as in multidimensional arrays, or when creating a new array). String - values maintain both pointer and length since embedded `NUL' + values maintain both pointer and length since embedded NUL characters are allowed. NOTE: By intent, strings are maintained using the current @@ -22001,7 +22790,7 @@ that use them. indicates what is in the `union'. Representing numbers is easy--the API uses a C `double'. Strings -require more work. Since `gawk' allows embedded `NUL' bytes in string +require more work. Since `gawk' allows embedded NUL bytes in string values, a string must be represented as a pair containing a data-pointer and length. This is the `awk_string_t' type. @@ -22081,7 +22870,7 @@ Requested: Scalar Scalar Scalar false false Value false false false false Cookie -Table 16.1: Value Types Returned +Table 16.1: API Value Types Returned File: gawk.info, Node: Memory Allocation Functions, Next: Constructor Functions, Prev: Requesting Values, Up: Extension API Description @@ -22124,6 +22913,7 @@ not return a value. `#define emalloc(pointer, type, size, message) ...' The arguments to this macro are as follows: + `pointer' The pointer variable to point at the allocated storage. @@ -22275,14 +23065,15 @@ File: gawk.info, Node: Exit Callback Functions, Next: Extension Version String .............................................. An "exit callback" function is a function that `gawk' calls before it -exits. Such functions are useful if you have general "clean up" tasks -that should be performed in your extension (such as closing data base +exits. Such functions are useful if you have general "cleanup" tasks +that should be performed in your extension (such as closing database connections or other resource deallocations). You can register such a function with `gawk' using the following function. `void awk_atexit(void (*funcp)(void *data, int exit_status),' ` void *arg0);' The parameters are: + `funcp' A pointer to the function to be called before `gawk' exits. The `data' parameter will be the original value of `arg0'. @@ -22371,7 +23162,8 @@ used for `RT', if any. A pointer to your `XXX_take_control_of()' function. `awk_const struct input_parser *awk_const next;' - This pointer is used by `gawk'. The extension cannot modify it. + This is for use by `gawk'; therefore it is marked `awk_const' so + that the extension cannot modify it. The steps are as follows: @@ -22410,8 +23202,8 @@ as follows: Otherwise, it will. `struct stat sbuf;' - If file descriptor is valid, then `gawk' will have filled in this - structure via a call to the `fstat()' system call. + If the file descriptor is valid, then `gawk' will have filled in + this structure via a call to the `fstat()' system call. The `XXX_can_take_file()' function should examine these fields and decide if the input parser should be used for the file. The decision @@ -22494,10 +23286,10 @@ need to test for a `NULL' value. `gawk' sets `*errcode' to zero, so there is no need to set it unless an error occurs. If an error does occur, the function should return `EOF' and set -`*errcode' to a non-zero value. In that case, if `*errcode' does not -equal -1, `gawk' automatically updates the `ERRNO' variable based on -the value of `*errcode'. (In general, setting `*errcode = errno' -should do the right thing.) +`*errcode' to a value greater than zero. In that case, if `*errcode' +does not equal zero, `gawk' automatically updates the `ERRNO' variable +based on the value of `*errcode'. (In general, setting `*errcode = +errno' should do the right thing.) As an alternative to supplying a function that returns an input record, you may instead supply a function that simply reads bytes, and @@ -22574,8 +23366,8 @@ an extension to take over the output to a file opened with the `>' or false otherwise. `awk_const struct output_wrapper *awk_const next;' - This is for use by `gawk'; therefore they are marked `awk_const' - so that the extension cannot modify them. + This is for use by `gawk'; therefore it is marked `awk_const' so + that the extension cannot modify it. The `awk_output_buf_t' structure looks like this: @@ -22632,9 +23424,9 @@ in the `awk_output_buf_t'. The data members are as follows: the `name' and `mode' fields, and any additional state (such as `awk' variable values) that is appropriate. - When `gawk' calls `XXX_take_control_of()', it should fill in the -other fields, as appropriate, except for `fp', which it should just use -normally. + When `gawk' calls `XXX_take_control_of()', that function should fill +in the other fields, as appropriate, except for `fp', which it should +just use normally. You register your output wrapper with the following function: @@ -22671,7 +23463,7 @@ structures as described earlier. `awk_bool_t (*can_take_two_way)(const char *name);' This function returns true if it wants to take over two-way I/O - for this filename. It should not change any state (variable + for this file name. It should not change any state (variable values, etc.) within `gawk'. `awk_bool_t (*take_control_of)(const char *name,' @@ -22682,8 +23474,8 @@ structures as described earlier. respectively. These structures were described earlier. `awk_const struct two_way_processor *awk_const next;' - This is for use by `gawk'; therefore they are marked `awk_const' - so that the extension cannot modify them. + This is for use by `gawk'; therefore it is marked `awk_const' so + that the extension cannot modify it. As with the input parser and output processor, you provide "yes I can take this" and "take over for this" functions, @@ -22852,7 +23644,7 @@ was discussed earlier, in *note General Data Types::. `awk_bool_t sym_update_scalar(awk_scalar_t cookie, awk_value_t *value);' Update the value associated with a scalar cookie. Return false if - the new value is not one of `AWK_STRING' or `AWK_NUMBER'. Here + the new value is not of type `AWK_STRING' or `AWK_NUMBER'. Here too, the built-in variables may not be updated. It is not obvious at first glance how to work with scalar cookies or @@ -22967,9 +23759,10 @@ follows: `awk_bool_t create_value(awk_value_t *value, awk_value_cookie_t *result);' Create a cached string or numeric value from `value' for efficient - later assignment. Only `AWK_NUMBER' and `AWK_STRING' values are - allowed. Any other type is rejected. While `AWK_UNDEFINED' could - be allowed, doing so would result in inferior performance. + later assignment. Only values of type `AWK_NUMBER' and + `AWK_STRING' are allowed. Any other type is rejected. While + `AWK_UNDEFINED' could be allowed, doing so would result in + inferior performance. `awk_bool_t release_value(awk_value_cookie_t vc);' Release the memory associated with a value cookie obtained from @@ -23023,13 +23816,13 @@ if `awk' code assigns a new value to `VAR1', are all the others be changed too?" That's a great question. The answer is that no, it's not a problem. -Internally, `gawk' uses reference-counted strings. This means that many -variables can share the same string value, and `gawk' keeps track of -the usage. When a variable's value changes, `gawk' simply decrements -the reference count on the old value and updates the variable to use -the new value. +Internally, `gawk' uses "reference-counted strings". This means that +many variables can share the same string value, and `gawk' keeps track +of the usage. When a variable's value changes, `gawk' simply +decrements the reference count on the old value and updates the +variable to use the new value. - Finally, as part of your clean up action (*note Exit Callback + Finally, as part of your cleanup action (*note Exit Callback Functions::) you should release any cached values that you created, using `release_value()'. @@ -23170,7 +23963,7 @@ The following functions relate to individual array elements. ` const awk_value_t *const value);' In the array represented by `a_cookie', create or modify the element whose index is given by `index'. The `ARGV' and `ENVIRON' - arrays may not be changed. + arrays may not be changed, although the `PROCINFO' array can be. `awk_bool_t set_array_element_by_elem(awk_array_t a_cookie,' ` awk_element_t element);' @@ -23408,8 +24201,8 @@ code: Thus, the correct way to build an array is to work "top down." Create the array, and immediately install it in `gawk''s symbol table using `sym_update()', or install it as an element in a - previously existing array using `set_element()'. We show example - code shortly. + previously existing array using `set_array_element()'. We show + example code shortly. 2. Due to gawk internals, after using `sym_update()' to install an array into `gawk', you have to retrieve the array cookie from the @@ -23599,13 +24392,15 @@ The API provides access to several variables that describe whether the corresponding command-line options were enabled when `gawk' was invoked. The variables are: +`do_debug' + This variable is true if `gawk' was invoked with `--debug' option. + `do_lint' This variable is true if `gawk' was invoked with `--lint' option (*note Options::). -`do_traditional' - This variable is true if `gawk' was invoked with `--traditional' - option. +`do_mpfr' + This variable is true if `gawk' was invoked with `--bignum' option. `do_profile' This variable is true if `gawk' was invoked with `--profile' @@ -23615,11 +24410,9 @@ invoked. The variables are: This variable is true if `gawk' was invoked with `--sandbox' option. -`do_debug' - This variable is true if `gawk' was invoked with `--debug' option. - -`do_mpfr' - This variable is true if `gawk' was invoked with `--bignum' option. +`do_traditional' + This variable is true if `gawk' was invoked with `--traditional' + option. The value of `do_lint' can change if `awk' code modifies the `LINT' built-in variable (*note Built-in Variables::). The others should not @@ -24219,7 +25012,9 @@ for loading each function into `gawk': static awk_ext_func_t func_table[] = { { "chdir", do_chdir, 1 }, { "stat", do_stat, 2 }, + #ifndef __MINGW32__ { "fts", do_fts, 3 }, + #endif }; Each extension must have a routine named `dl_load()' to load @@ -24230,8 +25025,7 @@ everything that needs to be loaded. It is simplest to use the dl_load_func(func_table, filefuncs, "") - And that's it! As an exercise, consider adding functions to -implement system calls such as `chown()', `chmod()', and `umask()'. + And that's it! ---------- Footnotes ---------- @@ -24284,8 +25078,8 @@ create a GNU/Linux shared library: } The `AWKLIBPATH' environment variable tells `gawk' where to find -shared libraries (*note Finding Extensions::). We set it to the -current directory and run the program: +extensions (*note Finding Extensions::). We set it to the current +directory and run the program: $ AWKLIBPATH=$PWD gawk -f testff.awk -| /tmp @@ -24315,7 +25109,7 @@ current directory and run the program: ---------- Footnotes ---------- (1) In practice, you would probably want to use the GNU -Autotools--Automake, Autoconf, Libtool, and Gettext--to configure and +Autotools--Automake, Autoconf, Libtool, and `gettext'--to configure and build your libraries. Instructions for doing so are beyond the scope of this Info file. *Note gawkextlib::, for WWW links to the tools. @@ -24358,7 +25152,7 @@ File: gawk.info, Node: Extension Sample File Functions, Next: Extension Sample The `filefuncs' extension provides three different functions, as follows: The usage is: -`@load "filefuncs"' +@load "filefuncs" This is how you load the extension. `result = chdir("/some/directory")' @@ -24367,7 +25161,7 @@ follows: The usage is: success or less than zero upon error. In the latter case it updates `ERRNO'. -`result = stat("/some/path", statdata [, follow])' +`result = stat("/some/path", statdata' [`, follow']`)' The `stat()' function provides a hook into the `stat()' system call. It returns zero upon success or less than zero upon error. In the latter case it updates `ERRNO'. @@ -24379,52 +25173,36 @@ follows: The usage is: successful, `stat()' fills the `statdata' array with information retrieved from the filesystem, as follows: - `statdata["name"]' The name of the file. - `statdata["dev"]' Corresponds to the `st_dev' field in - the `struct stat'. - `statdata["ino"]' Corresponds to the `st_ino' field in - the `struct stat'. - `statdata["mode"]' Corresponds to the `st_mode' field in - the `struct stat'. - `statdata["nlink"]' Corresponds to the `st_nlink' field in - the `struct stat'. - `statdata["uid"]' Corresponds to the `st_uid' field in - the `struct stat'. - `statdata["gid"]' Corresponds to the `st_gid' field in - the `struct stat'. - `statdata["size"]' Corresponds to the `st_size' field in - the `struct stat'. - `statdata["atime"]' Corresponds to the `st_atime' field in - the `struct stat'. - `statdata["mtime"]' Corresponds to the `st_mtime' field in - the `struct stat'. - `statdata["ctime"]' Corresponds to the `st_ctime' field in - the `struct stat'. - `statdata["rdev"]' Corresponds to the `st_rdev' field in - the `struct stat'. This element is - only present for device files. - `statdata["major"]' Corresponds to the `st_major' field in - the `struct stat'. This element is - only present for device files. - `statdata["minor"]' Corresponds to the `st_minor' field in - the `struct stat'. This element is - only present for device files. - `statdata["blksize"]' Corresponds to the `st_blksize' field - in the `struct stat', if this field is - present on your system. (It is present - on all modern systems that we know of.) - `statdata["pmode"]' A human-readable version of the mode - value, such as printed by `ls'. For - example, `"-rwxr-xr-x"'. - `statdata["linkval"]' If the named file is a symbolic link, - this element will exist and its value - is the value of the symbolic link - (where the symbolic link points to). - `statdata["type"]' The type of the file as a string. One - of `"file"', `"blockdev"', `"chardev"', - `"directory"', `"socket"', `"fifo"', - `"symlink"', `"door"', or `"unknown"'. - Not all systems support all file types. + Subscript Field in `struct stat' File type + ------------------------------------------------------------ + `"name"' The file name All + `"dev"' `st_dev' All + `"ino"' `st_ino' All + `"mode"' `st_mode' All + `"nlink"' `st_nlink' All + `"uid"' `st_uid' All + `"gid"' `st_gid' All + `"size"' `st_size' All + `"atime"' `st_atime' All + `"mtime"' `st_mtime' All + `"ctime"' `st_ctime' All + `"rdev"' `st_rdev' Device files + `"major"' `st_major' Device files + `"minor"' `st_minor' Device files + `"blksize"'`st_blksize' All + `"pmode"' A human-readable version of the All + mode value, such as printed by + `ls'. For example, + `"-rwxr-xr-x"' + `"linkval"'The value of the symbolic link Symbolic + links + `"type"' The type of the file as a string. All + One of `"file"', `"blockdev"', + `"chardev"', `"directory"', + `"socket"', `"fifo"', `"symlink"', + `"door"', or `"unknown"'. Not + all systems support all file + types. `flags = or(FTS_PHYSICAL, ...)' `result = fts(pathlist, flags, filedata)' @@ -24442,7 +25220,7 @@ requested hierarchies. The arguments are as follows: `pathlist' - An array of filenames. The element values are used; the index + An array of file names. The element values are used; the index values are ignored. `flags' @@ -24558,10 +25336,10 @@ constant (`FNM_NOMATCH'), and an array of flag values named `FNM'. The arguments to `fnmatch()' are: `pattern' - The filename wildcard to match. + The file name wildcard to match. `string' - The filename string. + The file name string. `flag' Either zero, or the bitwise OR of one or more of the flags in the @@ -24569,18 +25347,14 @@ constant (`FNM_NOMATCH'), and an array of flag values named `FNM'. The flags are follows: -`FNM["CASEFOLD"]' Corresponds to the `FNM_CASEFOLD' flag as defined in - `fnmatch()'. -`FNM["FILE_NAME"]' Corresponds to the `FNM_FILE_NAME' flag as defined - in `fnmatch()'. -`FNM["LEADING_DIR"]' Corresponds to the `FNM_LEADING_DIR' flag as defined - in `fnmatch()'. -`FNM["NOESCAPE"]' Corresponds to the `FNM_NOESCAPE' flag as defined in - `fnmatch()'. -`FNM["PATHNAME"]' Corresponds to the `FNM_PATHNAME' flag as defined in - `fnmatch()'. -`FNM["PERIOD"]' Corresponds to the `FNM_PERIOD' flag as defined in - `fnmatch()'. +Array element Corresponding flag defined by `fnmatch()' +-------------------------------------------------------------------------- +`FNM["CASEFOLD"]' `FNM_CASEFOLD' +`FNM["FILE_NAME"]' `FNM_FILE_NAME' +`FNM["LEADING_DIR"]'`FNM_LEADING_DIR' +`FNM["NOESCAPE"]' `FNM_NOESCAPE' +`FNM["PATHNAME"]' `FNM_PATHNAME' +`FNM["PERIOD"]' `FNM_PERIOD' Here is an example: @@ -24657,8 +25431,8 @@ standard output to a temporary file configured to have the same owner and permissions as the original. After the file has been processed, the extension restores standard output to its original destination. If `INPLACE_SUFFIX' is not an empty string, the original file is linked to -a backup filename created by appending that suffix. Finally, the -temporary file is renamed to the original filename. +a backup file name created by appending that suffix. Finally, the +temporary file is renamed to the original file name. If any error occurs, the extension issues a fatal error to terminate processing immediately without damaging the original file. @@ -24672,9 +25446,6 @@ processing immediately without damaging the original file. $ gawk -i inplace -v INPLACE_SUFFIX=.bak '{ gsub(/foo/, "bar") } > { print }' file1 file2 file3 - We leave it as an exercise to write a wrapper script that presents an -interface similar to `sed -i'. - File: gawk.info, Node: Extension Sample Ord, Next: Extension Sample Readdir, Prev: Extension Sample Inplace, Up: Extension Samples @@ -24718,10 +25489,11 @@ on the command line (or with `getline'), they are read, with each entry returned as a record. The record consists of three fields. The first two are the inode -number and the filename, separated by a forward slash character. On +number and the file name, separated by a forward slash character. On systems where the directory entry contains the file type, the record has a third field (also separated by a slash) which is a single letter -indicating the type of the file: +indicating the type of the file. The letters are file types are shown +in *note table-readdir-file-types::. Letter File Type -------------------------------------------------------------------------- @@ -24734,6 +25506,8 @@ Letter File Type `s' Socket `u' Anything else (unknown) +Table 16.2: File Types Returned By `readdir()' + On systems without the file type information, the third field is always `u'. @@ -24765,10 +25539,10 @@ unwary. Here is an example: BEGIN { REVOUT = 1 - print "hello, world" > "/dev/stdout" + print "don't panic" > "/dev/stdout" } - The output from this program is: `dlrow ,olleh'. + The output from this program is: `cinap t'nod'. File: gawk.info, Node: Extension Sample Rev2way, Next: Extension Sample Read write array, Prev: Extension Sample Revout, Up: Extension Samples @@ -24786,12 +25560,14 @@ example shows how to use it: BEGIN { cmd = "/magic/mirror" - print "hello, world" |& cmd + print "don't panic" |& cmd cmd |& getline result print result close(cmd) } + The output from this program is: `cinap t'nod'. + File: gawk.info, Node: Extension Sample Read write array, Next: Extension Sample Readfile, Prev: Extension Sample Rev2way, Up: Extension Samples @@ -24803,8 +25579,8 @@ The `rwarray' extension adds two functions, named `writea()' and `ret = writea(file, array)' This function takes a string argument, which is the name of the - file to which dump the array, and the array itself as the second - argument. `writea()' understands multidimensional arrays. It + file to which to dump the array, and the array itself as the + second argument. `writea()' understands arrays of arrays. It returns one on success, or zero upon failure. `ret = reada(file, array)' @@ -24887,9 +25663,8 @@ File: gawk.info, Node: Extension Sample Time, Prev: Extension Sample API Tests 16.7.12 Extension Time Functions -------------------------------- -These functions can be used either by invoking `gawk' with a -command-line argument of `-l time' or by inserting `@load "time"' in -your script. +The `time' extension adds two functions, named `gettimeofday()' and +`sleep()', as follows: `@load "time"' This is how you load the extension. @@ -24901,7 +25676,7 @@ your script. have sub-second precision, but the actual precision may vary based on the platform. If the standard C `gettimeofday()' system call is available on this platform, then it simply returns the value. - Otherwise, if on Windows, it tries to use + Otherwise, if on MS-Windows, it tries to use `GetSystemTimeAsFileTime()'. `result = sleep(SECONDS)' @@ -24914,7 +25689,7 @@ your script. delay. -File: gawk.info, Node: gawkextlib, Prev: Extension Samples, Up: Dynamic Extensions +File: gawk.info, Node: gawkextlib, Next: Extension summary, Prev: Extension Samples, Up: Dynamic Extensions 16.8 The `gawkextlib' Project ============================= @@ -24943,7 +25718,7 @@ Time::) was originally from this project but has been moved in to the main `gawk' distribution. You can check out the code for the `gawkextlib' project using the -GIT (http://git-scm.com) distributed source code control system. The +Git (http://git-scm.com) distributed source code control system. The command is as follows: git clone git://git.code.sf.net/p/gawkextlib/code gawkextlib-code @@ -24954,7 +25729,7 @@ parser library installed in order to build and use the XML extension. In addition, you must have the GNU Autotools installed (Autoconf (http://www.gnu.org/software/autoconf), Automake (http://www.gnu.org/software/automake), Libtool -(http://www.gnu.org/software/libtool), and Gettext +(http://www.gnu.org/software/libtool), and GNU `gettext' (http://www.gnu.org/software/gettext)). The simple recipe for building and testing `gawkextlib' is as @@ -24984,6 +25759,115 @@ users, please consider doing so through the `gawkextlib' project. See the project's web site for more information. +File: gawk.info, Node: Extension summary, Next: Extension Exercises, Prev: gawkextlib, Up: Dynamic Extensions + +16.9 Summary +============ + + * You can write extensions (sometimes called plug-ins) for `gawk' in + C or C++ using the Application Programming Interface (API) defined + by the `gawk' developers. + + * Extensions must have a license compatible with the GNU General + Public License (GPL), and they must assert that fact by declaring + a variable named `plugin_is_GPL_compatible'. + + * Communication between `gawk' and an extension is two-way. `gawk' + passes a `struct' to the extension which contains various data + fields and function pointers. The extension can then call into + `gawk' via the supplied function pointers to accomplish certain + tasks. + + * One of these tasks is to "register" the name and implementation of + a new `awk'-level function with `gawk'. The implementation takes + the form of a C function pointer with a defined signature. By + convention, implementation functions are named `do_XXXX()' for + some `awk'-level function `XXXX()'. + + * The API is defined in a header file named `gawkpi.h'. You must + include a number of standard header files _before_ including it in + your source file. + + * API function pointers are provided for the following kinds of + operations: + + * Registration functions. You may register extension functions, + exit callbacks, a version string, input parsers, output + wrappers, and two-way processors. + + * Printing fatal, warning, and "lint" warning messages. + + * Updating `ERRNO', or unsetting it. + + * Accessing parameters, including converting an undefined + parameter into an array. + + * Symbol table access: retrieving a global variable, creating + one, or changing one. + + * Allocating, reallocating, and releasing memory. + + * Creating and releasing cached values; this provides an + efficient way to use values for multiple variables and can be + a big performance win. + + * Manipulating arrays: retrieving, adding, deleting, and + modifying elements; getting the count of elements in an array; + creating a new array; clearing an array; and flattening an + array for easy C style looping over all its indices and + elements + + * The API defines a number of standard data types for representing + `awk' values, array elements, and arrays. + + * The API provide convenience functions for constructing values. It + also provides memory management functions to ensure compatibility + between memory allocated by `gawk' and memory allocated by an + extension. + + * _All_ memory passed from `gawk' to an extension must be treated as + read-only by the extension. + + * _All_ memory passed from an extension to `gawk' must come from the + API's memory allocation functions. `gawk' takes responsibility for + the memory and will release it when appropriate. + + * The API provides information about the running version of `gawk' so + that an extension can make sure it is compatible with the `gawk' + that loaded it. + + * It is easiest to start a new extension by copying the boilerplate + code described in this major node. Macros in the `gawkapi.h' make + this easier to do. + + * The `gawk' distribution includes a number of small but useful + sample extensions. The `gawkextlib' project includes several more, + larger, extensions. If you wish to write an extension and + contribute it to the community of `gawk' users, the `gawkextlib' + project should be the place to do so. + + + +File: gawk.info, Node: Extension Exercises, Prev: Extension summary, Up: Dynamic Extensions + +16.10 Exercises +=============== + + 1. Add functions to implement system calls such as `chown()', + `chmod()', and `umask()' to the file operations extension + presented in *note Internal File Ops::. + + 2. (Hard.) How would you provide namespaces in `gawk', so that the + names of functions in different extensions don't conflict with + each other? If you come up with a really good scheme, contact the + `gawk' maintainer to tell him about it. + + 3. Write a wrapper script that provides an interface similar to `sed + -i' for the "inplace" extension presented in *note Extension + Sample Inplace::. + + + File: gawk.info, Node: Language History, Next: Installation, Prev: Dynamic Extensions, Up: Top Appendix A The Evolution of the `awk' Language @@ -24994,7 +25878,7 @@ the POSIX specification. Many long-time `awk' users learned `awk' programming with the original `awk' implementation in Version 7 Unix. (This implementation was the basis for `awk' in Berkeley Unix, through 4.3-Reno. Subsequent versions of Berkeley Unix, and some systems -derived from 4.4BSD-Lite, use various versions of `gawk' for their +derived from 4.4BSD-Lite, used various versions of `gawk' for their `awk'.) This major node briefly describes the evolution of the `awk' language, with cross-references to other parts of the Info file where you can find more information. @@ -25014,6 +25898,7 @@ you can find more information. * Common Extensions:: Common Extensions Summary. * Ranges and Locales:: How locales used to affect regexp ranges. * Contributors:: The major contributors to `gawk'. +* History summary:: History summary. File: gawk.info, Node: V7/SVR3.1, Next: SVR4, Up: Language History @@ -25237,7 +26122,7 @@ the current version of `gawk'. - Indirect function calls (*note Indirect Calls::). - Directories on the command line produce a warning and are - skipped (*note Command line directories::). + skipped (*note Command-line directories::). * New keywords: @@ -25286,8 +26171,8 @@ the current version of `gawk'. - The `bindtextdomain()', `dcgettext()' and `dcngettext()' functions for internationalization (*note Programmer i18n::). - - The `fflush()' function from Brian Kernighan's version of - `awk' (*note I/O Functions::). + - The `fflush()' function from BWK `awk' (*note I/O + Functions::). - The `gensub()', `patsplit()', and `strtonum()' functions for more powerful text manipulation (*note String Functions::). @@ -25308,7 +26193,7 @@ the current version of `gawk'. `-r', `-S', `-t', and `-V' short options. Also, the ability to use GNU-style long-named options that start with `--' and the `--assign', `--bignum', `--characters-as-bytes', - `--copyright', `--debug', `--dump-variables', `--execle', + `--copyright', `--debug', `--dump-variables', `--exec', `--field-separator', `--file', `--gen-pot', `--help', `--include', `--lint', `--lint-old', `--load', `--non-decimal-data', `--optimize', `--posix', @@ -25344,6 +26229,13 @@ the current version of `gawk'. - GCC for VAX and Alpha has not been tested for a while. + * Support for the following obsolete systems was removed from the + code and the documentation for `gawk' version 4.1: + + - Ultrix + + * Support for MirBSD was removed at `gawk' version 4.2. + File: gawk.info, Node: Feature History, Next: Common Extensions, Prev: POSIX/GNU, Up: Language History @@ -25402,7 +26294,7 @@ in POSIX `awk', in the order they were added to `gawk'. * The ability to delete all of an array at once with `delete ARRAY' (*note Delete::). - * Command line option changes (*note Options::): + * Command-line option changes (*note Options::): - The ability to use GNU-style long-named options that start with `--'. @@ -25436,17 +26328,18 @@ in POSIX `awk', in the order they were added to `gawk'. * The `next file' statement became `nextfile' (*note Nextfile Statement::). - * The `fflush()' function from the Bell Laboratories research - version of `awk' (*note I/O Functions::). + * The `fflush()' function from BWK `awk' (then at Bell Laboratories; + *note I/O Functions::). - * New command line options: + * New command-line options: - The `--lint-old' option to warn about constructs that are not available in the original Version 7 Unix version of `awk' (*note V7/SVR3.1::). - - The `-m' option from the Bell Laboratories research version - of `awk' This was later removed. + - The `-m' option from BWK `awk'. (Brian was still at Bell + Laboratories at the time.) This was later removed from both + his `awk' and from `gawk'. - The `--re-interval' option to provide interval expressions in regexps (*note Regexp Operators::). @@ -25457,7 +26350,7 @@ in POSIX `awk', in the order they were added to `gawk'. * The use of GNU Autoconf to control the configuration process (*note Quick Installation::). - * Amiga support. + * Amiga support. This has since been removed. Version 3.1 of `gawk' introduced the following features: @@ -25516,7 +26409,7 @@ in POSIX `awk', in the order they were added to `gawk'. * The support for `next file' as two words was removed completely (*note Nextfile Statement::). - * Additional commnd line options (*note Options::): + * Additional command-line options (*note Options::): - The `--dump-variables' option to print a list of all global variables. @@ -25548,7 +26441,8 @@ in POSIX `awk', in the order they were added to `gawk'. * Tandem support. This was later removed. - * The Atari port became officially unsupported. + * The Atari port became officially unsupported and was later removed + entirely. * The source code changed to use ISO C standard-style function definitions. @@ -25605,13 +26499,13 @@ in POSIX `awk', in the order they were added to `gawk'. * An optional third argument to `asort()' and `asorti()', specifying how to sort (*note String Functions::). - * The behavior of `fflush()' changed to match Brian Kernighan's `awk' - and for POSIX; now both `fflush()' and `fflush("")' flush all open - output redirections (*note I/O Functions::). + * The behavior of `fflush()' changed to match BWK `awk' and for + POSIX; now both `fflush()' and `fflush("")' flush all open output + redirections (*note I/O Functions::). * The `isarray()' function which distinguishes if an item is an array - or not, to make it possible to traverse multidimensional arrays - (*note Type Functions::). + or not, to make it possible to traverse arrays of arrays (*note + Type Functions::). * The `patsplit()' function which gives the same capability as `FPAT', for splitting (*note String Functions::). @@ -25630,7 +26524,7 @@ in POSIX `awk', in the order they were added to `gawk'. * `switch' / `case' are enabled by default (*note Switch Statement::). - * Command line option changes (*note Options::): + * Command-line option changes (*note Options::): - The `-b' and `--characters-as-bytes' options which prevent `gawk' from treating input as a multibyte string. @@ -25648,7 +26542,7 @@ in POSIX `awk', in the order they were added to `gawk'. * Directories named on the command line now produce a warning, not a fatal error, unless `--posix' or `--traditional' are used (*note - Command line directories::). + Command-line directories::). * The `gawk' internals were rewritten, bringing the `dgawk' debugger and possibly improved performance (*note Debugger::). @@ -25697,10 +26591,10 @@ in POSIX `awk', in the order they were added to `gawk'. `PROCINFO["identifiers"]' (*note Auto-set::). * The three executables `gawk', `pgawk', and `dgawk', were merged - into one, named just `gawk'. As a result the command line options + into one, named just `gawk'. As a result the command-line options changed. - * Command line option changes (*note Options::): + * Command-line option changes (*note Options::): - The `-D' option invokes the debugger. @@ -25717,8 +26611,8 @@ in POSIX `awk', in the order they were added to `gawk'. - The `-R' option was removed. - * Support for high precision arithmetic with MPFR. (*note Gawk and - MPFR::). + * Support for high precision arithmetic with MPFR. (*note Arbitrary + Precision Arithmetic::). * The `and()', `or()' and `xor()' functions changed to allow any number of arguments, with a minimum of two (*note Bitwise @@ -25866,7 +26760,7 @@ and its rationale (http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd_chap09.html#tag_21_09_03_05). -File: gawk.info, Node: Contributors, Prev: Ranges and Locales, Up: Language History +File: gawk.info, Node: Contributors, Next: History summary, Prev: Ranges and Locales, Up: Language History A.9 Major Contributors to `gawk' ================================ @@ -25912,8 +26806,8 @@ Info file, in approximate chronological order: * Michal Jaegermann provided the port to Atari systems and its documentation. (This port is no longer supported.) He continues - to provide portability checking with DEC Alpha systems, and has - done a lot of work to make sure `gawk' works on non-32-bit systems. + to provide portability checking, and has done a lot of work to + make sure `gawk' works on non-32-bit systems. * Fred Fish provided the port to Amiga systems and its documentation. (With Fred's sad passing, this is no longer supported.) @@ -25978,8 +26872,7 @@ Info file, in approximate chronological order: - The modifications to convert `gawk' into a byte-code interpreter, including the debugger. - - The addition of true multidimensional arrays. *note Arrays - of Arrays::. + - The addition of true arrays of arrays. - The additional modifications for support of arbitrary precision arithmetic. @@ -25994,6 +26887,9 @@ Info file, in approximate chronological order: - The improved array sorting features were driven by John together with Pat Rankin. + * Panos Papadopoulos contributed the original text for *note Include + Files::. + * Efraim Yawitz contributed the original text for *note Debugger::. * The development of the extension API first released with `gawk' @@ -26009,6 +26905,38 @@ Info file, in approximate chronological order: 1994. +File: gawk.info, Node: History summary, Prev: Contributors, Up: Language History + +A.10 Summary +============ + + * The `awk' language has evolved over time. The first release was + with V7 Unix circa 1978. In 1987 for System V Release 3.1, major + additions, including user-defined functions, were made to the + language. Additional changes were made for System V Release 4, in + 1989. Since then, further minor changes happen under the auspices + of the POSIX standard. + + * Brian Kernighan's `awk' provides a small number of extensions that + are implemented in common with other versions of `awk'. + + * `gawk' provides a large number of extensions over POSIX `awk'. + They can be disabled with either the `--traditional' or `--posix' + options. + + * The interaction of POSIX locales and regexp matching in `gawk' has + been confusing over the years. Today, `gawk' implements Rational + Range Interpretation, where ranges of the form `[a-z]' match + _only_ the characters numerically between `a' through `z' in the + machine's native character set. Usually this is ASCII but it can + be EBCDIC on IBM S/390 systems. + + * Many people have contributed to `gawk' development over the years. + We hope that the list provided in this major node is complete and + gives the appropriate credit where credit is due. + + + File: gawk.info, Node: Installation, Next: Notes, Prev: Language History, Up: Top Appendix B Installing `gawk' @@ -26029,6 +26957,7 @@ people who did the respective ports. * Bugs:: Reporting Problems and Bugs. * Other Versions:: Other freely available `awk' implementations. +* Installation summary:: Summary of installation. File: gawk.info, Node: Gawk Distribution, Next: Unix Installation, Up: Installation @@ -26051,7 +26980,7 @@ File: gawk.info, Node: Getting, Next: Extracting, Up: Gawk Distribution B.1.1 Getting the `gawk' Distribution ------------------------------------- -There are three ways to get GNU software: +There are two ways to get GNU software: * Copy it from someone else who already has it. @@ -26083,7 +27012,6 @@ the GNU Zip program, `gzip'. use `gzip' to expand the file and then use `tar' to extract it. You can use the following pipeline to produce the `gawk' distribution: - # Under System V, add 'o' to the tar options gzip -d -c gawk-4.1.1.tar.gz | tar -xvpf - On a system with GNU `tar', you can let `tar' do the decompression @@ -26211,7 +27139,9 @@ Various `.c', `.y', and `.h' files `doc/igawk.1' The `troff' source for a manual page describing the `igawk' - program presented in *note Igawk Program::. + program presented in *note Igawk Program::. (Since `gawk' can do + its own `@include' processing, neither `igawk' nor `igawk.1' are + installed.) `doc/Makefile.in' The input file used during the configuration process to generate @@ -26219,8 +27149,8 @@ Various `.c', `.y', and `.h' files `Makefile.am' `*/Makefile.am' - Files used by the GNU `automake' software for generating the - `Makefile.in' files used by `autoconf' and `configure'. + Files used by the GNU Automake software for generating the + `Makefile.in' files used by Autoconf and `configure'. `Makefile.in' `aclocal.m4' @@ -26253,11 +27183,10 @@ Various `.c', `.y', and `.h' files contains a `Makefile.in' file, which `configure' uses to generate a `Makefile'. `Makefile.am' is used by GNU Automake to create `Makefile.in'. The library functions from *note Library - Functions::, and the `igawk' program from *note Igawk Program::, - are included as ready-to-use files in the `gawk' distribution. - They are installed as part of the installation process. The rest - of the programs in this Info file are available in appropriate - subdirectories of `awklib/eg'. + Functions::, are included as ready-to-use files in the `gawk' + distribution. They are installed as part of the installation + process. The rest of the programs in this Info file are available + in appropriate subdirectories of `awklib/eg'. `extension/*' The source code, manual pages, and infrastructure files for the @@ -26272,8 +27201,8 @@ Various `.c', `.y', and `.h' files PC Installation::, for details). `vms/*' - Files needed for building `gawk' under VMS (*note VMS - Installation::, for details). + Files needed for building `gawk' under Vax/VMS and OpenVMS (*note + VMS Installation::, for details). `test/*' A test suite for `gawk'. You can use `make check' from the @@ -26311,8 +27240,8 @@ environment for MS-Windows. `gawk-4.1.1'. Like most GNU software, `gawk' is configured automatically for your system by running the `configure' program. This program is a Bourne shell script that is generated automatically using -GNU `autoconf'. (The `autoconf' software is described fully starting -with *note (Autoconf)Top:: autoconf,Autoconf--Generating Automatic +GNU Autoconf. (The Autoconf software is described fully starting with +*note (Autoconf)Top:: autoconf,Autoconf--Generating Automatic Configuration Scripts.) To configure `gawk', simply run `configure': @@ -26390,8 +27319,8 @@ command line when compiling `gawk' from scratch, including: improvement. `--with-whiny-user-strftime' - Force use of the included version of the `strftime()' function for - deficient systems. + Force use of the included version of the C `strftime()' function + for deficient systems. Use the command `./configure --help' to see the full list of options that `configure' supplies. @@ -26435,9 +27364,9 @@ any constants that `configure' defined and should not have. `custom.h' is automatically included by `config.h'. It is also possible that the `configure' program generated by -`autoconf' will not work on your system in some other fashion. If you -do have a problem, the file `configure.ac' is the input for `autoconf'. -You may be able to change this file and generate a new version of +Autoconf will not work on your system in some other fashion. If you do +have a problem, the file `configure.ac' is the input for Autoconf. You +may be able to change this file and generate a new version of `configure' that works on your system (*note Bugs::, for information on how to report problems in configuring `gawk'). The same mechanism may be used to send in updates to `configure.ac' and/or `custom.h'. @@ -26466,14 +27395,14 @@ B.3.1 Installation on PC Operating Systems This minor node covers installation and usage of `gawk' on x86 machines running MS-DOS, any version of MS-Windows, or OS/2. In this minor node, the term "Windows32" refers to any of Microsoft -Windows-95/98/ME/NT/2000/XP/Vista/7. +Windows-95/98/ME/NT/2000/XP/Vista/7/8. - The limitations of MS-DOS (and MS-DOS shells under Windows32 or -OS/2) has meant that various "DOS extenders" are often used with -programs such as `gawk'. The varying capabilities of Microsoft Windows -3.1 and Windows32 can add to the confusion. For an overview of the -considerations, please refer to `README_d/README.pc' in the -distribution. + The limitations of MS-DOS (and MS-DOS shells under the other +operating systems) has meant that various "DOS extenders" are often +used with programs such as `gawk'. The varying capabilities of +Microsoft Windows 3.1 and Windows32 can add to the confusion. For an +overview of the considerations, please refer to `README_d/README.pc' in +the distribution. * Menu: @@ -26532,13 +27461,13 @@ B.3.1.2 Compiling `gawk' for PC Operating Systems ................................................. `gawk' can be compiled for MS-DOS, Windows32, and OS/2 using the GNU -development tools from DJ Delorie (DJGPP: MS-DOS only) or Eberhard -Mattes (EMX: MS-DOS, Windows32 and OS/2). The file -`README_d/README.pc' in the `gawk' distribution contains additional -notes, and `pc/Makefile' contains important information on compilation -options. +development tools from DJ Delorie (DJGPP: MS-DOS only), MinGW +(Windows32) or Eberhard Mattes (EMX: MS-DOS, Windows32 and OS/2). The +file `README_d/README.pc' in the `gawk' distribution contains +additional notes, and `pc/Makefile' contains important information on +compilation options. - To build `gawk' for MS-DOS and Windows32, copy the files in the `pc' +To build `gawk' for MS-DOS and Windows32, copy the files in the `pc' directory (_except_ for `ChangeLog') to the directory with the rest of the `gawk' sources, then invoke `make' with the appropriate target name as an argument to build `gawk'. The `Makefile' copied from the `pc' @@ -26598,7 +27527,12 @@ other set of (self-consistent) environment variables and compiler flags. NOTE: Ancient OS/2 ports of GNU `make' are not able to handle the Makefiles of this package. If you encounter any problems with `make', try GNU Make 3.79.1 or later versions. You should find - the latest version on `ftp://hobbes.nmsu.edu/pub/os2/'. + the latest version on `ftp://hobbes.nmsu.edu/pub/os2/'.(1) + + ---------- Footnotes ---------- + + (1) As of May, 2014, this site is still there, but the author could +not find a package for GNU Make. File: gawk.info, Node: PC Testing, Next: PC Using, Prev: PC Compiling, Up: PC Installation @@ -26639,11 +27573,11 @@ Networking::). EMX (OS/2 only) supports at least the `|&' operator. files as described in *note AWKPATH Variable::. However, semicolons (rather than colons) separate elements in the `AWKPATH' variable. If `AWKPATH' is not set or is empty, then the default search path for -MS-Windows and MS-DOS versions is `".;c:/lib/awk;c:/gnu/lib/awk"'. +MS-Windows and MS-DOS versions is `.;c:/lib/awk;c:/gnu/lib/awk'. The search path for OS/2 (32 bit, EMX) is determined by the prefix directory (most likely `/usr' or `c:/usr') that has been specified as -an option of the `configure' script like it is the case for the Unix +an option of the `configure' script as is the case for the Unix versions. If `c:/usr' is the prefix directory then the default search path contains `.' and `c:/usr/share/awk'. Additionally, to support binary distributions of `gawk' for OS/2 systems whose drive `c:' might @@ -26651,7 +27585,7 @@ not support long file names or might not exist at all, there is a special environment variable. If `UNIXROOT' specifies a drive then this specific drive is also searched for program files. E.g., if `UNIXROOT' is set to `e:' the complete default search path is -`".;c:/usr/share/awk;e:/usr/share/awk"'. +`.;c:/usr/share/awk;e:/usr/share/awk'. An `sh'-like shell (as opposed to `command.com' under MS-DOS or `cmd.exe' under MS-Windows or OS/2) may be useful for `awk' programming. @@ -26659,10 +27593,9 @@ The DJGPP collection of tools includes an MS-DOS port of Bash, and several shells are available for OS/2, including `ksh'. Under MS-Windows, OS/2 and MS-DOS, `gawk' (and many other text -programs) silently translate end-of-line `"\r\n"' to `"\n"' on input -and `"\n"' to `"\r\n"' on output. A special `BINMODE' variable -(c.e.) allows control over these translations and is interpreted as -follows: +programs) silently translate end-of-line `\r\n' to `\n' on input and +`\n' to `\r\n' on output. A special `BINMODE' variable (c.e.) allows +control over these translations and is interpreted as follows: * If `BINMODE' is `"r"', or one, then binary mode is set on read (i.e., no translations on reads). @@ -26688,11 +27621,11 @@ and cannot be changed mid-stream. Versions::). `mawk' and `gawk' handle `BINMODE' similarly; however, `mawk' adds a `-W BINMODE=N' option and an environment variable that can set `BINMODE', `RS', and `ORS'. The files `binmode[1-3].awk' -(under `gnu/lib/awk' in some of the prepared distributions) have been -chosen to match `mawk''s `-W BINMODE=N' option. These can be changed -or discarded; in particular, the setting of `RS' giving the fewest -"surprises" is open to debate. `mawk' uses `RS = "\r\n"' if binary -mode is set on read, which is appropriate for files with the +(under `gnu/lib/awk' in some of the prepared binary distributions) have +been chosen to match `mawk''s `-W BINMODE=N' option. These can be +changed or discarded; in particular, the setting of `RS' giving the +fewest "surprises" is open to debate. `mawk' uses `RS = "\r\n"' if +binary mode is set on read, which is appropriate for files with the MS-DOS-style end-of-line. To illustrate, the following examples set binary mode on writes for @@ -26709,7 +27642,7 @@ These give the same result as the `-W BINMODE=2' option in `mawk'. The following changes the record separator to `"\r\n"' and sets binary mode on reads, but does not affect the mode on standard input: - gawk -v RS="\r\n" --source "BEGIN { BINMODE = 1 }" ... + gawk -v RS="\r\n" -e "BEGIN { BINMODE = 1 }" ... or: @@ -26757,8 +27690,8 @@ translation of `"\r\n"', since it won't. Caveat Emptor! File: gawk.info, Node: VMS Installation, Prev: PC Installation, Up: Non-Unix Installation -B.3.2 How to Compile and Install `gawk' on VMS ----------------------------------------------- +B.3.2 How to Compile and Install `gawk' on Vax/VMS and OpenVMS +-------------------------------------------------------------- This node describes how to compile and install `gawk' under VMS. The older designation "VMS" is used throughout to refer to OpenVMS. @@ -26795,10 +27728,10 @@ or: $ MMK/DESCRIPTION=[.vms]descrip.mms gawk `MMK' is an open source, free, near-clone of `MMS' and can better -handle `ODS-5' volumes with upper- and lowercase filenames. `MMK' is +handle ODS-5 volumes with upper- and lowercase file names. `MMK' is available from `https://github.com/endlesssoftware/mmk'. - With `ODS-5' volumes and extended parsing enabled, the case of the + With ODS-5 volumes and extended parsing enabled, the case of the target parameter may need to be exact. `gawk' has been tested under VAX/VMS 7.3 and Alpha/VMS 7.3-1 using @@ -26806,8 +27739,8 @@ Compaq C V6.4, and Alpha/VMS 7.3, Alpha/VMS 7.3-2, and IA64/VMS 8.3. The most recent builds used HP C V7.3 on Alpha VMS 8.3 and both Alpha and IA64 VMS 8.4 used HP C 7.3.(1) - The `[.vms]gawk_build_steps.txt' provides information on how to build -`gawk' into a PCSI kit that is compatible with the GNV product. + *Note VMS GNV::, for information on building `gawk' as a PCSI kit +that is compatible with the GNV product. ---------- Footnotes ---------- @@ -26916,7 +27849,7 @@ has no device or directory path information in it, `gawk' looks in the current directory first, then in the directory specified by the translation of `AWK_LIBRARY' if the file is not found. If, after searching in both directories, the file still is not found, `gawk' -appends the suffix `.awk' to the filename and retries the file search. +appends the suffix `.awk' to the file name and retries the file search. If `AWK_LIBRARY' has no definition, a default value of `SYS$LIBRARY:' is used for it. @@ -27049,11 +27982,12 @@ get this information with the command `gawk --version'. Once you have a precise problem, send email to <bug-gawk@gnu.org>. - Using this address automatically sends a copy of your mail to me. -If necessary, I can be reached directly at <arnold@skeeve.com>. The -bug reporting address is preferred since the email list is archived at -the GNU Project. _All email should be in English, since that is my -native language._ + The `gawk' maintainers subscribe to this address and thus they will +receive your bug report. If necessary, the primary maintainer can be +reached directly at <arnold@skeeve.com>. The bug reporting address is +preferred since the email list is archived at the GNU Project. _All +email should be in English. This is the only language understood in +common by all the maintainers._ CAUTION: Do _not_ try to report bugs in `gawk' by posting to the Usenet/Internet newsgroup `comp.lang.awk'. While the `gawk' @@ -27088,7 +28022,7 @@ considered authoritative if it conflicts with this Info file. The people maintaining the non-Unix ports of `gawk' are as follows: MS-DOS with DJGPP Scott Deifik, <scottd.mail@sbcglobal.net>. -MS-Windows with MINGW Eli Zaretskii, <eliz@gnu.org>. +MS-Windows with MinGW Eli Zaretskii, <eliz@gnu.org>. OS/2 Andreas Buening, <andreas.buening@nexgo.de>. VMS Pat Rankin, <r.pat.rankin@gmail.com>, and John Malmberg, <wb8tyw@qsl.net>. @@ -27098,7 +28032,7 @@ z/OS (OS/390) Dave Pitts, <dpitts@cozx.com>. your report to the <bug-gawk@gnu.org> email list as well. -File: gawk.info, Node: Other Versions, Prev: Bugs, Up: Installation +File: gawk.info, Node: Other Versions, Next: Installation summary, Prev: Bugs, Up: Installation B.5 Other Freely Available `awk' Implementations ================================================ @@ -27107,7 +28041,7 @@ B.5 Other Freely Available `awk' Implementations `// Do C++ comments work? answer: yes! of course' -- Michael Brennan - There are a number of other freely available `awk' implementations. +There are a number of other freely available `awk' implementations. This minor node briefly describes where to get them: Unix `awk' @@ -27176,11 +28110,11 @@ Unix `awk' since approximately 2003. `pawk' - Nelson H.F. Beebe at the University of Utah has modified Brian - Kernighan's `awk' to provide timing and profiling information. It - is different from `gawk' with the `--profile' option. (*note - Profiling::), in that it uses CPU-based profiling, not line-count - profiling. You may find it at either + Nelson H.F. Beebe at the University of Utah has modified BWK `awk' + to provide timing and profiling information. It is different from + `gawk' with the `--profile' option. (*note Profiling::), in that + it uses CPU-based profiling, not line-count profiling. You may + find it at either `ftp://ftp.math.utah.edu/pub/pawk/pawk-20030606.tar.gz' or `http://www.math.utah.edu/pub/pawk/pawk-20030606.tar.gz'. @@ -27194,12 +28128,13 @@ Busybox Awk (http://busybox.net). The OpenSolaris POSIX `awk' - The version of `awk' in `/usr/xpg4/bin' on Solaris is more-or-less - POSIX-compliant. It is based on the `awk' from Mortice Kern - Systems for PCs. This author was able to make it compile and work - under GNU/Linux with 1-2 hours of work. Making it more generally - portable (using GNU Autoconf and/or Automake) would take more - work, and this has not been done, at least to our knowledge. + The versions of `awk' in `/usr/xpg4/bin' and `/usr/xpg6/bin' on + Solaris are more-or-less POSIX-compliant. They are based on the + `awk' from Mortice Kern Systems for PCs. This author was able to + make this code compile and work under GNU/Linux with 1-2 hours of + work. Making it more generally portable (using GNU Autoconf + and/or Automake) would take more work, and this has not been done, + at least to our knowledge. The source code used to be available from the OpenSolaris web site. However, that project was ended and the web site shut down. @@ -27224,7 +28159,7 @@ Libmawk This is a Python module that claims to bring `awk'-like features to Python. See `https://github.com/alecthomas/pawk' for more information. (This is not related to Nelson Beebe's modified - version of Brian Kernighan's `awk', described earlier.) + version of BWK `awk', described earlier.) QSE Awk This is an embeddable `awk' interpreter. For more information see @@ -27237,6 +28172,9 @@ QSE Awk `http://www.quiktrim.org/QTawk.html' for more information, including the manual and a download link. + The project may also be frozen; no new code changes have been made + since approximately 2008. + Other Versions See also the Wikipedia article (http://en.wikipedia.org/wiki/Awk_language#Versions_and_implementations), @@ -27244,6 +28182,34 @@ Other Versions +File: gawk.info, Node: Installation summary, Prev: Other Versions, Up: Installation + +B.6 Summary +=========== + + * The `gawk' distribution is available from GNU project's main + distribution site, `ftp.gnu.org'. The canonical build recipe is: + + wget http://ftp.gnu.org/gnu/gawk/gawk-4.1.1.tar.gz + tar -xvpzf gawk-4.1.1.tar.gz + cd gawk-4.1.1 + ./configure && make && make check + + * `gawk' may be built on non-POSIX systems as well. The currently + supported systems are MS-Windows using DJGPP, MSYS, MinGW and + Cygwin, OS/2 using EMX, and both Vax/VMS and OpenVMS. + Instructions for each system are included in this major node. + + * Bug reports should be sent via email to <bug-gawk@gnu.org>. Bug + reports should be in English, and should include the version of + `gawk', how it was compiled, and a short program and data file + which demonstrate the problem. + + * There are a number of other freely available `awk' + implementations. Many are POSIX compliant; others are less so. + + + File: gawk.info, Node: Notes, Next: Basic Concepts, Prev: Installation, Up: Top Appendix C Implementation Notes @@ -27262,6 +28228,7 @@ and maintainers of `gawk'. Everything in it applies specifically to * Implementation Limitations:: Some limitations of the implementation. * Extension Design:: Design notes about the extension API. * Old Extension Mechanism:: Some compatibility for old extensions. +* Notes summary:: Summary of implementation notes. File: gawk.info, Node: Compatibility Mode, Next: Additions, Up: Notes @@ -27279,7 +28246,7 @@ one more option available on the command line: `-Y' `--parsedebug' - Prints out the parse stack information as the program is being + Print out the parse stack information as the program is being parsed. This option is intended only for serious `gawk' developers and not @@ -27307,8 +28274,8 @@ as well as any considerations you should bear in mind. `gawk'. * New Ports:: Porting `gawk' to a new operating system. -* Derived Files:: Why derived files are kept in the - `git' repository. +* Derived Files:: Why derived files are kept in the Git + repository. File: gawk.info, Node: Accessing The Source, Next: Adding Code, Up: Additions @@ -27329,9 +28296,9 @@ doesn't have it. Once you have done so, use the command: git clone git://git.savannah.gnu.org/gawk.git -This will clone the `gawk' repository. If you are behind a firewall -that will not allow you to use the Git native protocol, you can still -access the repository using: +This clones the `gawk' repository. If you are behind a firewall that +does not allow you to use the Git native protocol, you can still access +the repository using: git clone http://git.savannah.gnu.org/r/gawk.git @@ -27353,7 +28320,7 @@ C.2.2 Adding New Features You are free to add any new features you like to `gawk'. However, if you want your changes to be incorporated into the `gawk' distribution, there are several steps that you need to take in order to make it -possible to include your changes: +possible to include them: 1. Before building the new feature into `gawk' itself, consider writing it as an extension module (*note Dynamic Extensions::). @@ -27370,9 +28337,10 @@ possible to include your changes: 3. Get the latest version. It is much easier for me to integrate changes if they are relative to the most recent distributed - version of `gawk'. If your version of `gawk' is very old, I may - not be able to integrate them at all. (*Note Getting::, for - information on getting the latest version of `gawk'.) + version of `gawk', or better yet, relative to the latest code in + the Git repository. If your version of `gawk' is very old, I may + not be able to integrate your changes at all. (*Note Getting::, + for information on getting the latest version of `gawk'.) 4. See *note (Version)Top:: standards, GNU Coding Standards. This document describes how GNU software should be written. If you @@ -27469,7 +28437,8 @@ possible to include your changes: 8. Include an entry for the `ChangeLog' file with your submission. This helps further minimize the amount of work I have to do, - making it easier for me to accept patches. + making it easier for me to accept patches. It is simplest if you + just make this part of your diff. Although this sounds like a lot of work, please remember that while you may write the new code, I have to maintain it and support it. If it @@ -27510,18 +28479,24 @@ steps: people. Thus, you should not change them unless it is for a very good reason; i.e., changes are not out of the question, but changes to these files are scrutinized extra carefully. The files - are `dfa.c', `dfa.h', `getopt1.c', `getopt.c', `getopt.h', - `install-sh', `mkinstalldirs', `regcomp.c', `regex.c', - `regexec.c', `regexex.c', `regex.h', `regex_internal.c', and - `regex_internal.h'. - - 5. Be willing to continue to maintain the port. Non-Unix operating + are `dfa.c', `dfa.h', `getopt.c', `getopt.h', `getopt1.c', + `getopt_int.h', `gettext.h', `regcomp.c', `regex.c', `regex.h', + `regex_internal.c', `regex_internal.h', and `regexec.c'. + + 5. A number of other files are provided by the GNU Autotools + (Autoconf, Automake, and GNU `gettext'). You should not change + them either, unless it is for a very good reason. The files are + `ABOUT-NLS', `config.guess', `config.rpath', `config.sub', + `depcomp', `INSTALL', `install-sh', `missing', `mkinstalldirs', + `xalloc.h', and `ylwrap'. + + 6. Be willing to continue to maintain the port. Non-Unix operating systems are supported by volunteers who maintain the code needed to compile and run `gawk' on their systems. If noone volunteers to maintain a port, it becomes unsupported and it may be necessary to remove it from the distribution. - 6. Supply an appropriate `gawkmisc.???' file. Each port has its own + 7. Supply an appropriate `gawkmisc.???' file. Each port has its own `gawkmisc.???' that implements certain operating system specific functions. This is cleaner than a plethora of `#ifdef's scattered throughout the code. The `gawkmisc.c' in the main source @@ -27537,7 +28512,7 @@ steps: (Currently, this is only an issue for the PC operating system ports.) - 7. Supply a `Makefile' as well as any other C source and header files + 8. Supply a `Makefile' as well as any other C source and header files that are necessary for your operating system. All your code should be in a separate subdirectory, with a name that is the same as, or reminiscent of, either your operating system or the @@ -27547,7 +28522,7 @@ steps: avoid using names for your files that duplicate the names of files in the main source directory. - 8. Update the documentation. Please write a section (or sections) + 9. Update the documentation. Please write a section (or sections) for this Info file describing the installation and compilation steps needed to compile and/or install `gawk' for your system. @@ -27561,21 +28536,21 @@ style and brace layout that suits your taste. File: gawk.info, Node: Derived Files, Prev: New Ports, Up: Additions -C.2.4 Why Generated Files Are Kept In `git' -------------------------------------------- +C.2.4 Why Generated Files Are Kept In Git +----------------------------------------- -If you look at the `gawk' source in the `git' repository, you will -notice that it includes files that are automatically generated by GNU -infrastructure tools, such as `Makefile.in' from `automake' and even -`configure' from `autoconf'. +If you look at the `gawk' source in the Git repository, you will notice +that it includes files that are automatically generated by GNU +infrastructure tools, such as `Makefile.in' from Automake and even +`configure' from Autoconf. This is different from many Free Software projects that do not store the derived files, because that keeps the repository less cluttered, and it is easier to see the substantive changes when comparing versions and trying to understand what changed between commits. - However, there are two reasons why the `gawk' maintainer likes to -have everything in the repository. + However, there are several reasons why the `gawk' maintainer likes +to have everything in the repository. First, because it is then easy to reproduce any given version completely, without relying upon the availability of (older, likely @@ -27594,10 +28569,10 @@ build?) If the repository has all the generated files, then it's easy to just check them out and build. (Or _easier_, depending upon how far -back we go. `:-)') +back we go.) And that brings us to the second (and stronger) reason why all the -files really need to be in `git'. It boils down to who do you cater +files really need to be in Git. It boils down to who do you cater to--the `gawk' developer(s), or the user who just wants to check out a version and try it out? @@ -27623,11 +28598,18 @@ idea how to create it, and that was not the only problem.) He felt _extremely_ frustrated. With respect to that branch, the maintainer is no different than Jane User who wants to try to build -`gawk-4.0-stable' or `master' from the repository. +`gawk-4.1-stable' or `master' from the repository. Thus, the maintainer thinks that it's not just important, but critical, that for any given branch, the above incantation _just works_. + A third reason to have all the files is that without them, using `git +bisect' to try to find the commit that introduced a bug is exceedingly +difficult. The maintainer tried to do that on another project that +requires running bootstrapping scripts just to create `configure' and +so on; it was really painful. When the repository is self-contained, +using `git bisect' in it is very easy. + What are some of the consequences and/or actions to take? 1. We don't mind that there are differing files in the different @@ -27638,32 +28620,26 @@ critical, that for any given branch, the above incantation _just works_. B. He is really good at `git diff x y > /tmp/diff1 ; gvim /tmp/diff1' to remove the diffs that aren't of interest in - order to review code. `:-)' + order to review code. 2. It would certainly help if everyone used the same versions of the GNU tools as he does, which in general are the latest released - versions of `automake', `autoconf', `bison', and `gettext'. + versions of Automake, Autoconf, `bison', and GNU `gettext'. - A. Installing from source is quite easy. It's how the maintainer - worked for years under Fedora. He had `/usr/local/bin' at - the front of his `PATH' and just did: - - wget http://ftp.gnu.org/gnu/PACKAGE/PACKAGE-X.Y.Z.tar.gz - tar -xpzvf PACKAGE-X.Y.Z.tar.gz - cd PACKAGE-X.Y.Z - ./configure && make && make check - make install # as root - - B. These days the maintainer uses Ubuntu 12.04 which is medium - current, but he is already doing the above for `autoconf', - `automake' and `bison'. + Installing from source is quite easy. It's how the maintainer + worked for years (and still works). He had `/usr/local/bin' at + the front of his `PATH' and just did: + wget http://ftp.gnu.org/gnu/PACKAGE/PACKAGE-X.Y.Z.tar.gz + tar -xpzvf PACKAGE-X.Y.Z.tar.gz + cd PACKAGE-X.Y.Z + ./configure && make && make check + make install # as root Most of the above was originally written by the maintainer to other `gawk' developers. It raised the objection from one of the developers -"... that anybody pulling down the source from `git' is not an end -user." +"... that anybody pulling down the source from Git is not an end user." However, this is not true. There are "power `awk' users" who can build `gawk' (using the magic incantation shown previously) but who @@ -27672,12 +28648,12 @@ all the time. It was then suggested that there be a `cron' job to create nightly tarballs of "the source." Here, the problem is that there are source -trees, corresponding to the various branches! So, nightly tar balls +trees, corresponding to the various branches! So, nightly tarballs aren't the answer, especially as the repository can go for weeks without significant change being introduced. - Fortunately, the `git' server can meet this need. For any given -branch named BRANCHNAME, use: + Fortunately, the Git server can meet this need. For any given branch +named BRANCHNAME, use: wget http://git.savannah.gnu.org/cgit/gawk.git/snapshot/gawk-BRANCHNAME.tar.gz @@ -27688,9 +28664,9 @@ to retrieve a snapshot of the given branch. (1) We tried. It was painful. (2) There is one GNU program that is (in our opinion) severely -difficult to bootstrap from the `git' repository. For example, on the -author's old (but still working) PowerPC macintosh with Mac OS X 10.5, -it was necessary to bootstrap a ton of software, starting with `git' +difficult to bootstrap from the Git repository. For example, on the +author's old (but still working) PowerPC Macintosh with Mac OS X 10.5, +it was necessary to bootstrap a ton of software, starting with Git itself, in order to try to work with the latest code. It's not pleasant, and especially on older systems, it's a big waste of time. @@ -27698,8 +28674,8 @@ pleasant, and especially on older systems, it's a big waste of time. maintainers had dropped `.gz' and `.bz2' files and only distribute `.tar.xz' files. It was necessary to bootstrap `xz' first! - (3) A branch created by one of the other developers that did not -include the generated files. + (3) A branch (since removed) created by one of the other developers +that did not include the generated files. File: gawk.info, Node: Future Extensions, Next: Implementation Limitations, Prev: Additions, Up: Notes @@ -27712,11 +28688,11 @@ C.3 Probable Future Extensions Hey! -- Larry Wall - The `TODO' file in the `gawk' Git repository lists possible future -enhancements. Some of these relate to the source code, and others to -possible new features. Please see that file for the list. *Note -Additions::, if you are interested in tackling any of the projects -listed there. + The `TODO' file in the `master' branch of the `gawk' Git repository +lists possible future enhancements. Some of these relate to the source +code, and others to possible new features. Please see that file for +the list. *Note Additions::, if you are interested in tackling any of +the projects listed there. File: gawk.info, Node: Implementation Limitations, Next: Extension Design, Prev: Future Extensions, Up: Notes @@ -27732,7 +28708,7 @@ Item Limit -------------------------------------------------------------------------- Characters in a character 2^(number of bits per byte) class -Length of input record `MAX_INT ' +Length of input record `MAX_INT' Length of output record Unlimited Length of source line Unlimited Number of fields in a record `MAX_LONG' @@ -27745,9 +28721,9 @@ Number of pipe redirections min(number of processes per user, number of open files) Numeric values Double-precision floating point (if not using MPFR) -Size of a field `MAX_INT ' -Size of a literal string `MAX_INT ' -Size of a printf string `MAX_INT ' +Size of a field `MAX_INT' +Size of a literal string `MAX_INT' +Size of a printf string `MAX_INT' File: gawk.info, Node: Extension Design, Next: Old Extension Mechanism, Prev: Implementation Limitations, Up: Notes @@ -27793,9 +28769,9 @@ The old extension mechanism had several problems: * Being able to call into `gawk' from an extension required linker facilities that are common on Unix-derived systems but that did - not work on Windows systems; users wanting extensions on Windows - had to statically link them into `gawk', even though Windows - supports dynamic loading of shared objects. + not work on MS-Windows systems; users wanting extensions on + MS-Windows had to statically link them into `gawk', even though + MS-Windows supports dynamic loading of shared objects. * The API would change occasionally as `gawk' changed; no compatibility between versions was ever offered or planned for. @@ -27843,8 +28819,8 @@ Some goals for the new API were: flattening") in order to loop over all the element in an easy fashion for C code. - - The ability to create arrays (including `gawk''s true - multidimensional arrays). + - The ability to create arrays (including `gawk''s true arrays + of arrays). Some additional important goals were: @@ -27858,7 +28834,7 @@ Some goals for the new API were: * The API mechanism should not require access to `gawk''s symbols(1) by the compile-time or dynamic linker, in order to enable creation - of extensions that also work on Windows. + of extensions that also work on MS-Windows. During development, it became clear that there were other features that should be available to extensions, which were also subsequently @@ -27871,7 +28847,7 @@ provided: hook into input processing, output processing, and two-way I/O. * An extension should be able to provide a "call back" function to - perform clean up actions when `gawk' exits. + perform cleanup actions when `gawk' exits. * An extension should be able to provide a version string so that `gawk''s `--version' option can provide information about @@ -27896,7 +28872,7 @@ Mechanism Outline::, for the details. (1) The "symbols" are the variables and functions defined inside `gawk'. Access to these symbols by code external to `gawk' loaded -dynamically at runtime is problematic on Windows. +dynamically at runtime is problematic on MS-Windows. File: gawk.info, Node: Extension Other Design Decisions, Next: Extension Future Growth, Prev: Extension New Mechanism Goals, Up: Extension Design @@ -27964,7 +28940,7 @@ The API can later be expanded, in two ways: respect to any of the above. -File: gawk.info, Node: Old Extension Mechanism, Prev: Extension Design, Up: Notes +File: gawk.info, Node: Old Extension Mechanism, Next: Notes summary, Prev: Extension Design, Up: Notes C.6 Compatibility For Old Extensions ==================================== @@ -28002,6 +28978,37 @@ old extensions that you may have to use the new API described in *note Dynamic Extensions::. +File: gawk.info, Node: Notes summary, Prev: Old Extension Mechanism, Up: Notes + +C.7 Summary +=========== + + * `gawk''s extensions can be disabled with either the + `--traditional' option or with the `--posix' option. The + `--parsedebug' option is available if `gawk' is compiled with + `-DDEBUG'. + + * The source code for `gawk' is maintained in a publicly accessible + Git repository. Anyone may check it out and view the source. + + * Contributions to `gawk' are welcome. Following the steps outlined + in this major node will make it easier to integrate your + contributions into the code base. This applies both to new + feature contributions and to ports to additional operating systems. + + * `gawk' has some limits--generally those that are imposed by the + machine architecture. + + * The extension API design was intended to solve a number of problems + with the previous extension mechanism, enable features needed by + the `xgawk' project, and provide binary compatibility going + forward. + + * The previous extension mechanism is still supported in version 4.1 + of `gawk', but it _will_ be removed in the next major release. + + + File: gawk.info, Node: Basic Concepts, Next: Glossary, Prev: Notes, Up: Top Appendix D Basic Programming Concepts @@ -28138,7 +29145,7 @@ characters that comprise them. Individual variables, as well as numeric and string variables, are referred to as "scalar" values. Groups of values, such as arrays, are not scalars. - *note General Arithmetic::, provided a basic introduction to numeric + *note Computer Arithmetic::, provided a basic introduction to numeric types (integer and floating-point) and how they are used in a computer. Please review that information, including a number of caveats that were presented. @@ -28152,15 +29159,14 @@ like this: `""'. Humans are used to working in decimal; i.e., base 10. In base 10, numbers go from 0 to 9, and then "roll over" into the next column. -(Remember grade school? 42 is 4 times 10 plus 2.) +(Remember grade school? 42 = 4 x 10 + 2.) There are other number bases though. Computers commonly use base 2 or "binary", base 8 or "octal", and base 16 or "hexadecimal". In binary, each column represents two times the value in the column to its right. Each column may contain either a 0 or a 1. Thus, binary 1010 -represents 1 times 8, plus 0 times 4, plus 1 times 2, plus 0 times 1, -or decimal 10. Octal and hexadecimal are discussed more in *note -Nondecimal-numbers::. +represents (1 x 8) + (0 x 4) + (1 x 2) + (0 x 1), or decimal 10. Octal +and hexadecimal are discussed more in *note Nondecimal-numbers::. At the very lowest level, computers store values as groups of binary digits, or "bits". Modern computers group bits into groups of eight, @@ -28192,8 +29198,7 @@ Glossary Action A series of `awk' statements attached to a rule. If the rule's pattern matches an input record, `awk' executes the rule's action. - Actions are always enclosed in curly braces. (*Note Action - Overview::.) + Actions are always enclosed in braces. (*Note Action Overview::.) Amazing `awk' Assembler Henry Spencer at the University of Toronto wrote a retargetable @@ -28279,9 +29284,9 @@ Boolean Expression Bourne Shell The standard shell (`/bin/sh') on Unix and Unix-like systems, - originally written by Steven R. Bourne. Many shells (Bash, `ksh', - `pdksh', `zsh') are generally upwardly compatible with the Bourne - shell. + originally written by Steven R. Bourne at Bell Laboratories. Many + shells (Bash, `ksh', `pdksh', `zsh') are generally upwardly + compatible with the Bourne shell. Built-in Function The `awk' language provides built-in functions that perform various @@ -28302,7 +29307,8 @@ Built-in Variable Variables::.) Braces - See "Curly Braces." + The characters `{' and `}'. Braces are used in `awk' for + delimiting actions, compound statements, and function bodies. C The system programming language that most GNU software is written @@ -28323,8 +29329,8 @@ Character Set ASCII (American Standard Code for Information Interchange). Many European countries use an extension of ASCII known as ISO-8859-1 (ISO Latin-1). The Unicode character set (http://www.unicode.org) - is becoming increasingly popular and standard, and is particularly - widely used on GNU/Linux systems. + is increasingly popular and standard, and is particularly widely + used on GNU/Linux systems. CHEM A preprocessor for `pic' that reads descriptions of molecules and @@ -28334,7 +29340,7 @@ CHEM Cookie A peculiar goodie, token, saying or remembrance produced by or - presented to a program. (With thanks to Doug McIlroy.) + presented to a program. (With thanks to Professor Doug McIlroy.) Coprocess A subordinate program with which two-way communications is @@ -28369,8 +29375,7 @@ Comparison Expression process. (*Note Typing and Comparison::.) Curly Braces - The characters `{' and `}'. Curly braces are used in `awk' for - delimiting actions, compound statements, and function bodies. + See "Braces." Dark Corner An area in the language where specifications often were (or still @@ -28410,8 +29415,8 @@ Dynamic Regular Expression (*Note Computed Regexps::.) Environment - A collection of strings, of the form NAME`='`val', that each - program has available to it. Users generally place values into the + A collection of strings, of the form `NAME=VAL', that each program + has available to it. Users generally place values into the environment in order to provide information to various programs. Typical examples are the environment variables `HOME' and `PATH'. @@ -28461,11 +29466,11 @@ Floating-Point Number See also "Double Precision" and "Single Precision." Format - Format strings are used to control the appearance of output in the - `strftime()' and `sprintf()' functions, and are used in the - `printf' statement as well. Also, data conversions from numbers - to strings are controlled by the format strings contained in the - built-in variables `CONVFMT' and `OFMT'. (*Note Control Letters::.) + Format strings control the appearance of output in the + `strftime()' and `sprintf()' functions, and in the `printf' + statement as well. Also, data conversions from numbers to strings + are controlled by the format strings contained in the built-in + variables `CONVFMT' and `OFMT'. (*Note Control Letters::.) Free Documentation License This document describes the terms under which this Info file is @@ -28520,8 +29525,8 @@ Hexadecimal Base 16 notation, where the digits are `0'-`9' and `A'-`F', with `A' representing 10, `B' representing 11, and so on, up to `F' for 15. Hexadecimal numbers are written in C using a leading `0x', to - indicate their base. Thus, `0x12' is 18 (1 times 16 plus 2). - *Note Nondecimal-numbers::. + indicate their base. Thus, `0x12' is 18 ((1 x 16) + 2). *Note + Nondecimal-numbers::. I/O Abbreviation for "Input/Output," the act of moving data into and/or @@ -28578,7 +29583,7 @@ Keyword `gawk''s keywords are: `BEGIN', `BEGINFILE', `END', `ENDFILE', `break', `case', `continue', `default' `delete', `do...while', `else', `exit', `for...in', `for', `function', `func', `if', - `nextfile', `next', `switch', and `while'. + `next', `nextfile', `switch', and `while'. Lesser General Public License This document describes the terms under which binary library @@ -28634,11 +29639,7 @@ Number Octal Base-eight notation, where the digits are `0'-`7'. Octal numbers are written in C using a leading `0', to indicate their base. - Thus, `013' is 11 (one times 8 plus 3). *Note - Nondecimal-numbers::. - -P1003.1 - See "POSIX." + Thus, `013' is 11 ((1 x 8) + 3). *Note Nondecimal-numbers::. Pattern Patterns tell `awk' which input records are interesting to which @@ -28679,9 +29680,9 @@ Range (of input lines) specify single lines. (*Note Pattern Overview::.) Recursion - When a function calls itself, either directly or indirectly. As - long as this is not clear, refer to the entry for "recursion." If - this is clear, stop, and proceed to the next entry. + When a function calls itself, either directly or indirectly. If + this is clear, stop, and proceed to the next entry. Otherwise, + refer to the entry for "recursion." Redirection Redirection means performing input from something other than the @@ -28762,8 +29763,8 @@ Single Precision parts. Single precision numbers keep track of fewer digits than do double precision numbers, but operations on them are sometimes less expensive in terms of CPU time. This is the type used by - some very old versions of `awk' to store numeric values. It is - the C type `float'. + some ancient versions of `awk' to store numeric values. It is the + C type `float'. Space The character generated by hitting the space bar on the keyboard. @@ -28797,7 +29798,7 @@ Text Domain Timestamp A value in the "seconds since the epoch" format used by Unix and POSIX systems. Used for the `gawk' functions `mktime()', - `strftime()', and `systime()'. See also "Epoch" and "UTC." + `strftime()', and `systime()'. See also "Epoch," "GMT," and "UTC." Unix A computer operating system originally developed in the early @@ -30036,7 +31037,7 @@ Index * Menu: * ! (exclamation point), ! operator: Boolean Ops. (line 67) -* ! (exclamation point), ! operator <1>: Egrep Program. (line 170) +* ! (exclamation point), ! operator <1>: Egrep Program. (line 175) * ! (exclamation point), ! operator <2>: Ranges. (line 48) * ! (exclamation point), ! operator: Precedence. (line 52) * ! (exclamation point), != operator <1>: Precedence. (line 65) @@ -30048,12 +31049,11 @@ Index * ! (exclamation point), !~ operator <3>: Comparison Operators. (line 11) * ! (exclamation point), !~ operator <4>: Regexp Constants. (line 6) -* ! (exclamation point), !~ operator <5>: Computed Regexps. (line 6) -* ! (exclamation point), !~ operator <6>: Case-sensitivity. (line 26) +* ! (exclamation point), !~ operator <5>: Case-sensitivity. (line 26) +* ! (exclamation point), !~ operator <6>: Computed Regexps. (line 6) * ! (exclamation point), !~ operator: Regexp Usage. (line 19) -* " (double quote) in shell commands: Read Terminal. (line 25) -* " (double quote), in regexp constants: Computed Regexps. (line 28) -* " (double quote), in shell commands: Quoting. (line 37) +* " (double quote), in regexp constants: Computed Regexps. (line 29) +* " (double quote), in shell commands: Quoting. (line 54) * # (number sign), #! (executable scripts): Executable Scripts. (line 6) * # (number sign), commenting: Comments. (line 6) @@ -30064,46 +31064,46 @@ Index * $ (dollar sign), regexp operator: Regexp Operators. (line 35) * % (percent sign), % operator: Precedence. (line 55) * % (percent sign), %= operator <1>: Precedence. (line 95) -* % (percent sign), %= operator: Assignment Ops. (line 129) +* % (percent sign), %= operator: Assignment Ops. (line 130) * & (ampersand), && operator <1>: Precedence. (line 86) * & (ampersand), && operator: Boolean Ops. (line 57) * & (ampersand), gsub()/gensub()/sub() functions and: Gory Details. (line 6) * ' (single quote): One-shot. (line 15) * ' (single quote) in gawk command lines: Long. (line 33) -* ' (single quote), in shell commands: Quoting. (line 31) +* ' (single quote), in shell commands: Quoting. (line 48) * ' (single quote), vs. apostrophe: Comments. (line 27) -* ' (single quote), with double quotes: Quoting. (line 53) +* ' (single quote), with double quotes: Quoting. (line 70) * () (parentheses), in a profile: Profiling. (line 146) -* () (parentheses), regexp operator: Regexp Operators. (line 79) +* () (parentheses), regexp operator: Regexp Operators. (line 81) * * (asterisk), * operator, as multiplication operator: Precedence. (line 55) * * (asterisk), * operator, as regexp operator: Regexp Operators. - (line 87) + (line 89) * * (asterisk), * operator, null strings, matching: Gory Details. - (line 164) + (line 143) * * (asterisk), ** operator <1>: Precedence. (line 49) * * (asterisk), ** operator: Arithmetic Ops. (line 81) * * (asterisk), **= operator <1>: Precedence. (line 95) -* * (asterisk), **= operator: Assignment Ops. (line 129) +* * (asterisk), **= operator: Assignment Ops. (line 130) * * (asterisk), *= operator <1>: Precedence. (line 95) -* * (asterisk), *= operator: Assignment Ops. (line 129) +* * (asterisk), *= operator: Assignment Ops. (line 130) * + (plus sign), + operator: Precedence. (line 52) * + (plus sign), ++ operator <1>: Precedence. (line 46) * + (plus sign), ++ operator: Increment Ops. (line 11) * + (plus sign), += operator <1>: Precedence. (line 95) * + (plus sign), += operator: Assignment Ops. (line 82) -* + (plus sign), regexp operator: Regexp Operators. (line 102) +* + (plus sign), regexp operator: Regexp Operators. (line 105) * , (comma), in range patterns: Ranges. (line 6) * - (hyphen), - operator: Precedence. (line 52) * - (hyphen), -- operator <1>: Precedence. (line 46) * - (hyphen), -- operator: Increment Ops. (line 48) * - (hyphen), -= operator <1>: Precedence. (line 95) -* - (hyphen), -= operator: Assignment Ops. (line 129) +* - (hyphen), -= operator: Assignment Ops. (line 130) * - (hyphen), filenames beginning with: Options. (line 59) * - (hyphen), in bracket expressions: Bracket Expressions. (line 17) * --assign option: Options. (line 32) -* --bignum option: Options. (line 201) +* --bignum option: Options. (line 205) * --characters-as-bytes option: Options. (line 68) * --copyright option: Options. (line 88) * --debug option: Options. (line 108) @@ -30123,32 +31123,32 @@ Index * --gen-pot option: Options. (line 147) * --help option: Options. (line 154) * --include option: Options. (line 159) -* --lint option <1>: Options. (line 182) +* --lint option <1>: Options. (line 185) * --lint option: Command Line. (line 20) -* --lint-old option: Options. (line 288) +* --lint-old option: Options. (line 293) * --load option: Options. (line 173) * --non-decimal-data option <1>: Nondecimal Data. (line 6) -* --non-decimal-data option: Options. (line 207) +* --non-decimal-data option: Options. (line 211) * --non-decimal-data option, strtonum() function and: Nondecimal Data. (line 36) -* --optimize option: Options. (line 228) -* --posix option: Options. (line 247) -* --posix option, --traditional option and: Options. (line 266) -* --pretty-print option: Options. (line 220) +* --optimize option: Options. (line 235) +* --posix option: Options. (line 252) +* --posix option, --traditional option and: Options. (line 271) +* --pretty-print option: Options. (line 224) * --profile option <1>: Profiling. (line 12) -* --profile option: Options. (line 235) -* --re-interval option: Options. (line 272) -* --sandbox option: Options. (line 279) +* --profile option: Options. (line 240) +* --re-interval option: Options. (line 277) +* --sandbox option: Options. (line 284) * --sandbox option, disabling system() function: I/O Functions. - (line 94) + (line 97) * --sandbox option, input redirection with getline: Getline. (line 19) * --sandbox option, output redirection with print, printf: Redirection. (line 6) * --source option: Options. (line 117) * --traditional option: Options. (line 81) -* --traditional option, --posix option and: Options. (line 266) -* --use-lc-numeric option: Options. (line 215) -* --version option: Options. (line 293) +* --traditional option, --posix option and: Options. (line 271) +* --use-lc-numeric option: Options. (line 219) +* --version option: Options. (line 298) * --with-whiny-user-strftime configuration option: Additional Configuration Options. (line 35) * -b option: Options. (line 68) @@ -30156,50 +31156,51 @@ Index * -c option: Options. (line 81) * -D option: Options. (line 108) * -d option: Options. (line 93) +* -e option: Options. (line 333) * -E option: Options. (line 125) * -e option: Options. (line 117) * -f option: Options. (line 25) * -F option: Options. (line 21) * -f option: Long. (line 12) -* -F option, -Ft sets FS to TAB: Options. (line 301) -* -F option, command line: Command Line Field Separator. +* -F option, -Ft sets FS to TAB: Options. (line 306) +* -F option, command-line: Command Line Field Separator. (line 6) -* -f option, multiple uses: Options. (line 306) +* -f option, multiple uses: Options. (line 311) * -g option: Options. (line 147) * -h option: Options. (line 154) * -i option: Options. (line 159) -* -L option: Options. (line 288) +* -L option: Options. (line 293) * -l option: Options. (line 173) -* -M option: Options. (line 201) -* -N option: Options. (line 215) -* -n option: Options. (line 207) -* -O option: Options. (line 228) -* -o option: Options. (line 220) -* -P option: Options. (line 247) -* -p option: Options. (line 235) -* -r option: Options. (line 272) -* -S option: Options. (line 279) +* -M option: Options. (line 205) +* -N option: Options. (line 219) +* -n option: Options. (line 211) +* -O option: Options. (line 235) +* -o option: Options. (line 224) +* -P option: Options. (line 252) +* -p option: Options. (line 240) +* -r option: Options. (line 277) +* -S option: Options. (line 284) * -v option: Assignment Options. (line 12) -* -V option: Options. (line 293) +* -V option: Options. (line 298) * -v option: Options. (line 32) * -W option: Options. (line 46) -* . (period), regexp operator: Regexp Operators. (line 43) -* .gmo files: Explaining gettext. (line 41) -* .gmo files, converting from .po: I18N Example. (line 62) +* . (period), regexp operator: Regexp Operators. (line 44) +* .gmo files: Explaining gettext. (line 42) * .gmo files, specifying directory of <1>: Programmer i18n. (line 47) -* .gmo files, specifying directory of: Explaining gettext. (line 53) +* .gmo files, specifying directory of: Explaining gettext. (line 54) +* .mo files, converting from .po: I18N Example. (line 63) * .po files <1>: Translator i18n. (line 6) -* .po files: Explaining gettext. (line 36) -* .po files, converting to .gmo: I18N Example. (line 62) -* .pot files: Explaining gettext. (line 30) +* .po files: Explaining gettext. (line 37) +* .po files, converting to .mo: I18N Example. (line 63) +* .pot files: Explaining gettext. (line 31) * / (forward slash) to enclose regular expressions: Regexp. (line 10) * / (forward slash), / operator: Precedence. (line 55) * / (forward slash), /= operator <1>: Precedence. (line 95) -* / (forward slash), /= operator: Assignment Ops. (line 129) +* / (forward slash), /= operator: Assignment Ops. (line 130) * / (forward slash), /= operator, vs. /=.../ regexp constant: Assignment Ops. - (line 147) + (line 148) * / (forward slash), patterns and: Expression Patterns. (line 24) -* /= operator vs. /=.../ regexp constant: Assignment Ops. (line 147) +* /= operator vs. /=.../ regexp constant: Assignment Ops. (line 148) * /dev/... special files: Special FD. (line 46) * /dev/fd/N special files (gawk): Special FD. (line 46) * /inet/... special files (gawk): TCP/IP Networking. (line 6) @@ -30236,13 +31237,16 @@ Index * ? (question mark), regexp operator <1>: GNU Regexp Operators. (line 59) * ? (question mark), regexp operator: Regexp Operators. (line 111) -* [] (square brackets), regexp operator: Regexp Operators. (line 55) +* @-notation for indirect function calls: Indirect Calls. (line 47) +* @include directive: Include Files. (line 8) +* @load directive: Loading Shared Libraries. + (line 8) +* [] (square brackets), regexp operator: Regexp Operators. (line 56) * \ (backslash): Comments. (line 50) -* \ (backslash) in shell commands: Read Terminal. (line 25) -* \ (backslash), \" escape sequence: Escape Sequences. (line 76) +* \ (backslash), \" escape sequence: Escape Sequences. (line 84) * \ (backslash), \' operator (gawk): GNU Regexp Operators. (line 56) -* \ (backslash), \/ escape sequence: Escape Sequences. (line 69) +* \ (backslash), \/ escape sequence: Escape Sequences. (line 75) * \ (backslash), \< operator (gawk): GNU Regexp Operators. (line 30) * \ (backslash), \> operator (gawk): GNU Regexp Operators. @@ -30272,7 +31276,6 @@ Index (line 38) * \ (backslash), as field separator: Command Line Field Separator. (line 27) -* \ (backslash), continuing lines and <1>: Egrep Program. (line 220) * \ (backslash), continuing lines and: Statements/Lines. (line 19) * \ (backslash), continuing lines and, comments and: Statements/Lines. (line 76) @@ -30283,24 +31286,24 @@ Index * \ (backslash), in bracket expressions: Bracket Expressions. (line 17) * \ (backslash), in escape sequences: Escape Sequences. (line 6) * \ (backslash), in escape sequences, POSIX and: Escape Sequences. - (line 112) -* \ (backslash), in regexp constants: Computed Regexps. (line 28) -* \ (backslash), in shell commands: Quoting. (line 31) + (line 120) +* \ (backslash), in regexp constants: Computed Regexps. (line 29) +* \ (backslash), in shell commands: Quoting. (line 48) * \ (backslash), regexp operator: Regexp Operators. (line 18) * ^ (caret), ^ operator: Precedence. (line 49) * ^ (caret), ^= operator <1>: Precedence. (line 95) -* ^ (caret), ^= operator: Assignment Ops. (line 129) +* ^ (caret), ^= operator: Assignment Ops. (line 130) * ^ (caret), in bracket expressions: Bracket Expressions. (line 17) * ^ (caret), in FS: Regexp Field Splitting. (line 59) * ^ (caret), regexp operator <1>: GNU Regexp Operators. (line 59) * ^ (caret), regexp operator: Regexp Operators. (line 22) -* _ (underscore), C macro: Explaining gettext. (line 70) +* _ (underscore), C macro: Explaining gettext. (line 71) * _ (underscore), in names of private variables: Library Names. (line 29) * _ (underscore), translatable string: Programmer i18n. (line 69) -* _gr_init() user-defined function: Group Functions. (line 82) +* _gr_init() user-defined function: Group Functions. (line 83) * _ord_init() user-defined function: Ordinal Functions. (line 16) * _pw_init() user-defined function: Passwd Functions. (line 105) * accessing fields: Fields. (line 6) @@ -30312,7 +31315,7 @@ Index * actions, control statements in: Statements. (line 6) * actions, default: Very Simple. (line 34) * actions, empty: Very Simple. (line 39) -* Ada programming language: Glossary. (line 20) +* Ada programming language: Glossary. (line 19) * adding, features to gawk: Adding Code. (line 6) * adding, fields: Changing Fields. (line 53) * advanced features, fixed-width data: Constant Size. (line 10) @@ -30320,7 +31323,7 @@ Index * advanced features, network programming: TCP/IP Networking. (line 6) * advanced features, nondecimal input data: Nondecimal Data. (line 6) * advanced features, processes, communicating with: Two-way I/O. - (line 23) + (line 6) * advanced features, specifying field content: Splitting By Content. (line 10) * Aho, Alfred <1>: Contributors. (line 11) @@ -30330,11 +31333,10 @@ Index * algorithms: Basic High Level. (line 68) * allocating memory for extensions: Memory Allocation Functions. (line 6) -* Alpha (DEC): Manual History. (line 28) -* amazing awk assembler (aaa): Glossary. (line 12) -* amazingly workable formatter (awf): Glossary. (line 25) +* amazing awk assembler (aaa): Glossary. (line 11) +* amazingly workable formatter (awf): Glossary. (line 24) * ambiguity, syntactic: /= operator vs. /=.../ regexp constant: Assignment Ops. - (line 147) + (line 148) * ampersand (&), && operator <1>: Precedence. (line 86) * ampersand (&), && operator: Boolean Ops. (line 57) * ampersand (&), gsub()/gensub()/sub() functions and: Gory Details. @@ -30344,7 +31346,7 @@ Index * and: Bitwise Functions. (line 39) * AND bitwise operation: Bitwise Functions. (line 6) * and Boolean-logic operator: Boolean Ops. (line 6) -* ANSI: Glossary. (line 35) +* ANSI: Glossary. (line 34) * API informational variables: Extension API Informational Variables. (line 6) * API version: Extension Versioning. @@ -30355,18 +31357,18 @@ Index (line 6) * archeologists: Bugs. (line 6) * arctangent: Numeric Functions. (line 11) -* ARGC/ARGV variables: Auto-set. (line 11) +* ARGC/ARGV variables: Auto-set. (line 15) * ARGC/ARGV variables, command-line arguments: Other Arguments. (line 12) * ARGC/ARGV variables, how to use: ARGC and ARGV. (line 6) -* ARGC/ARGV variables, portability and: Executable Scripts. (line 42) -* ARGIND variable: Auto-set. (line 40) +* ARGC/ARGV variables, portability and: Executable Scripts. (line 59) +* ARGIND variable: Auto-set. (line 44) * ARGIND variable, command-line arguments: Other Arguments. (line 12) * arguments, command-line <1>: ARGC and ARGV. (line 6) -* arguments, command-line <2>: Auto-set. (line 11) +* arguments, command-line <2>: Auto-set. (line 15) * arguments, command-line: Other Arguments. (line 6) * arguments, command-line, invoking awk: Command Line. (line 6) -* arguments, in function calls: Function Calls. (line 16) +* arguments, in function calls: Function Calls. (line 18) * arguments, processing: Getopt Function. (line 6) * ARGV array, indexing into: Other Arguments. (line 12) * arithmetic operators: Arithmetic Ops. (line 6) @@ -30374,15 +31376,15 @@ Index * array members: Reference to Elements. (line 6) * array scanning order, controlling: Controlling Scanning. - (line 12) -* array, number of elements: String Functions. (line 194) + (line 14) +* array, number of elements: String Functions. (line 197) * arrays: Arrays. (line 6) * arrays of arrays: Arrays of Arrays. (line 6) * arrays, an example of using: Array Example. (line 6) -* arrays, and IGNORECASE variable: Array Intro. (line 91) +* arrays, and IGNORECASE variable: Array Intro. (line 94) * arrays, as parameters to functions: Pass By Value/Reference. (line 47) -* arrays, associative: Array Intro. (line 49) +* arrays, associative: Array Intro. (line 50) * arrays, associative, library functions and: Library Names. (line 57) * arrays, deleting entire contents: Delete. (line 39) * arrays, elements that don't exist: Reference to Elements. @@ -30391,9 +31393,9 @@ Index * arrays, elements, deleting: Delete. (line 6) * arrays, elements, order of access by in operator: Scanning an Array. (line 48) -* arrays, elements, retrieving number of: String Functions. (line 32) +* arrays, elements, retrieving number of: String Functions. (line 42) * arrays, for statement and: Scanning an Array. (line 20) -* arrays, indexing: Array Intro. (line 49) +* arrays, indexing: Array Intro. (line 50) * arrays, merging into strings: Join Function. (line 6) * arrays, multidimensional: Multidimensional. (line 10) * arrays, multidimensional, scanning: Multiscanning. (line 11) @@ -30407,7 +31409,7 @@ Index (line 6) * arrays, sorting, and IGNORECASE variable: Array Sorting Functions. (line 83) -* arrays, sparse: Array Intro. (line 70) +* arrays, sparse: Array Intro. (line 72) * arrays, subscripts, uninitialized variables as: Uninitialized Subscripts. (line 6) * arrays, unassigned elements: Reference to Elements. @@ -30418,12 +31420,12 @@ Index * ASCII: Ordinal Functions. (line 45) * asort <1>: Array Sorting Functions. (line 6) -* asort: String Functions. (line 32) +* asort: String Functions. (line 42) * asort() function (gawk), arrays, sorting: Array Sorting Functions. (line 6) * asorti <1>: Array Sorting Functions. (line 6) -* asorti: String Functions. (line 32) +* asorti: String Functions. (line 42) * asorti() function (gawk), arrays, sorting: Array Sorting Functions. (line 6) * assert() function (C library): Assert Function. (line 6) @@ -30435,29 +31437,29 @@ Index * assignment operators, evaluation order: Assignment Ops. (line 111) * assignment operators, lvalues/rvalues: Assignment Ops. (line 32) * assignments as filenames: Ignoring Assigns. (line 6) -* associative arrays: Array Intro. (line 49) +* associative arrays: Array Intro. (line 50) * asterisk (*), * operator, as multiplication operator: Precedence. (line 55) * asterisk (*), * operator, as regexp operator: Regexp Operators. - (line 87) + (line 89) * asterisk (*), * operator, null strings, matching: Gory Details. - (line 164) + (line 143) * asterisk (*), ** operator <1>: Precedence. (line 49) * asterisk (*), ** operator: Arithmetic Ops. (line 81) * asterisk (*), **= operator <1>: Precedence. (line 95) -* asterisk (*), **= operator: Assignment Ops. (line 129) +* asterisk (*), **= operator: Assignment Ops. (line 130) * asterisk (*), *= operator <1>: Precedence. (line 95) -* asterisk (*), *= operator: Assignment Ops. (line 129) +* asterisk (*), *= operator: Assignment Ops. (line 130) * atan2: Numeric Functions. (line 11) * automatic displays, in debugger: Debugger Info. (line 24) -* awf (amazingly workable formatter) program: Glossary. (line 25) +* awf (amazingly workable formatter) program: Glossary. (line 24) * awk debugging, enabling: Options. (line 108) -* awk language, POSIX version: Assignment Ops. (line 136) -* awk profiling, enabling: Options. (line 235) +* awk language, POSIX version: Assignment Ops. (line 137) +* awk profiling, enabling: Options. (line 240) * awk programs <1>: Two Rules. (line 6) * awk programs <2>: Executable Scripts. (line 6) * awk programs: Getting Started. (line 12) -* awk programs, complex: When. (line 29) +* awk programs, complex: When. (line 27) * awk programs, documenting <1>: Library Names. (line 6) * awk programs, documenting: Comments. (line 6) * awk programs, examples of: Sample Programs. (line 6) @@ -30477,25 +31479,24 @@ Index (line 6) * awk, function of: Getting Started. (line 6) * awk, gawk and <1>: This Manual. (line 14) -* awk, gawk and: Preface. (line 23) +* awk, gawk and: Preface. (line 21) * awk, history of: History. (line 17) * awk, implementation issues, pipes: Redirection. (line 135) * awk, implementations: Other Versions. (line 6) * awk, implementations, limits: Getline Notes. (line 14) * awk, invoking: Command Line. (line 6) * awk, new vs. old: Names. (line 6) -* awk, new vs. old, OFMT variable: Conversion. (line 55) -* awk, POSIX and: Preface. (line 23) -* awk, POSIX and, See Also POSIX awk: Preface. (line 23) +* awk, new vs. old, OFMT variable: Strings And Numbers. (line 57) +* awk, POSIX and: Preface. (line 21) +* awk, POSIX and, See Also POSIX awk: Preface. (line 21) * awk, regexp constants and: Comparison Operators. (line 102) -* awk, See Also gawk: Preface. (line 36) +* awk, See Also gawk: Preface. (line 34) * awk, terms describing: This Manual. (line 6) * awk, uses for <1>: When. (line 6) * awk, uses for <2>: Getting Started. (line 12) -* awk, uses for: Preface. (line 23) -* awk, versions of <1>: V7/SVR3.1. (line 6) -* awk, versions of: Names. (line 10) +* awk, uses for: Preface. (line 21) +* awk, versions of: V7/SVR3.1. (line 6) * awk, versions of, changes between SVR3.1 and SVR4: SVR4. (line 6) * awk, versions of, changes between SVR4 and POSIX awk: POSIX. (line 6) @@ -30512,11 +31513,10 @@ Index * awkvars.out file: Options. (line 93) * b debugger command (alias for break): Breakpoint Control. (line 11) * backslash (\): Comments. (line 50) -* backslash (\) in shell commands: Read Terminal. (line 25) -* backslash (\), \" escape sequence: Escape Sequences. (line 76) +* backslash (\), \" escape sequence: Escape Sequences. (line 84) * backslash (\), \' operator (gawk): GNU Regexp Operators. (line 56) -* backslash (\), \/ escape sequence: Escape Sequences. (line 69) +* backslash (\), \/ escape sequence: Escape Sequences. (line 75) * backslash (\), \< operator (gawk): GNU Regexp Operators. (line 30) * backslash (\), \> operator (gawk): GNU Regexp Operators. @@ -30546,7 +31546,6 @@ Index (line 38) * backslash (\), as field separator: Command Line Field Separator. (line 27) -* backslash (\), continuing lines and <1>: Egrep Program. (line 220) * backslash (\), continuing lines and: Statements/Lines. (line 19) * backslash (\), continuing lines and, comments and: Statements/Lines. (line 76) @@ -30557,9 +31556,9 @@ Index * backslash (\), in bracket expressions: Bracket Expressions. (line 17) * backslash (\), in escape sequences: Escape Sequences. (line 6) * backslash (\), in escape sequences, POSIX and: Escape Sequences. - (line 112) -* backslash (\), in regexp constants: Computed Regexps. (line 28) -* backslash (\), in shell commands: Quoting. (line 31) + (line 120) +* backslash (\), in regexp constants: Computed Regexps. (line 29) +* backslash (\), in shell commands: Quoting. (line 48) * backslash (\), regexp operator: Regexp Operators. (line 18) * backtrace debugger command: Execution Stack. (line 13) * Beebe, Nelson H.F. <1>: Other Versions. (line 78) @@ -30575,9 +31574,9 @@ Index * BEGIN pattern, getline and: Getline Notes. (line 19) * BEGIN pattern, headings, adding: Print Examples. (line 43) * BEGIN pattern, next/nextfile statements and <1>: Next Statement. - (line 45) + (line 44) * BEGIN pattern, next/nextfile statements and: I/O And BEGIN/END. - (line 37) + (line 36) * BEGIN pattern, OFS/ORS variables, assigning values to: Output Separators. (line 20) * BEGIN pattern, operators and: Using BEGIN/END. (line 17) @@ -30593,14 +31592,14 @@ Index * Benzinger, Michael: Contributors. (line 97) * Berry, Karl <1>: Ranges and Locales. (line 74) * Berry, Karl: Acknowledgments. (line 33) -* binary input/output: User-modified. (line 10) +* binary input/output: User-modified. (line 15) * bindtextdomain <1>: Programmer i18n. (line 47) * bindtextdomain: I18N Functions. (line 12) -* bindtextdomain() function (C library): Explaining gettext. (line 49) +* bindtextdomain() function (C library): Explaining gettext. (line 50) * bindtextdomain() function (gawk), portability and: I18N Portability. (line 33) * BINMODE variable <1>: PC Using. (line 33) -* BINMODE variable: User-modified. (line 10) +* BINMODE variable: User-modified. (line 15) * bit-manipulation functions: Bitwise Functions. (line 6) * bits2str() user-defined function: Bitwise Functions. (line 70) * bitwise AND: Bitwise Functions. (line 39) @@ -30620,17 +31619,17 @@ Index * braces ({}), actions and: Action Overview. (line 19) * braces ({}), statements, grouping: Statements. (line 10) * bracket expressions <1>: Bracket Expressions. (line 6) -* bracket expressions: Regexp Operators. (line 55) +* bracket expressions: Regexp Operators. (line 56) * bracket expressions, character classes: Bracket Expressions. - (line 30) + (line 32) * bracket expressions, collating elements: Bracket Expressions. - (line 69) + (line 79) * bracket expressions, collating symbols: Bracket Expressions. - (line 76) -* bracket expressions, complemented: Regexp Operators. (line 63) + (line 86) +* bracket expressions, complemented: Regexp Operators. (line 64) * bracket expressions, equivalence classes: Bracket Expressions. - (line 82) -* bracket expressions, non-ASCII: Bracket Expressions. (line 69) + (line 92) +* bracket expressions, non-ASCII: Bracket Expressions. (line 79) * bracket expressions, range expressions: Bracket Expressions. (line 6) * break debugger command: Breakpoint Control. (line 11) @@ -30644,16 +31643,16 @@ Index * breakpoint, how to disable or enable: Breakpoint Control. (line 69) * breakpoint, setting: Breakpoint Control. (line 11) * Brennan, Michael <1>: Other Versions. (line 6) -* Brennan, Michael <2>: Two-way I/O. (line 6) -* Brennan, Michael <3>: Simple Sed. (line 25) -* Brennan, Michael <4>: Delete. (line 56) +* Brennan, Michael <2>: Simple Sed. (line 25) +* Brennan, Michael <3>: Delete. (line 56) +* Brennan, Michael <4>: Acknowledgments. (line 76) * Brennan, Michael: Foreword. (line 83) -* Brian Kernighan's awk <1>: I/O Functions. (line 40) -* Brian Kernighan's awk <2>: Gory Details. (line 15) +* Brian Kernighan's awk <1>: I/O Functions. (line 43) +* Brian Kernighan's awk <2>: Gory Details. (line 19) * Brian Kernighan's awk <3>: String Functions. (line 490) * Brian Kernighan's awk <4>: Delete. (line 48) * Brian Kernighan's awk <5>: Nextfile Statement. (line 47) -* Brian Kernighan's awk <6>: Continue Statement. (line 43) +* Brian Kernighan's awk <6>: Continue Statement. (line 44) * Brian Kernighan's awk <7>: Break Statement. (line 51) * Brian Kernighan's awk <8>: I/O And BEGIN/END. (line 16) * Brian Kernighan's awk <9>: Concatenation. (line 36) @@ -30662,23 +31661,23 @@ Index (line 67) * Brian Kernighan's awk <12>: GNU Regexp Operators. (line 83) -* Brian Kernighan's awk <13>: Escape Sequences. (line 116) -* Brian Kernighan's awk <14>: When. (line 21) -* Brian Kernighan's awk: Preface. (line 15) +* Brian Kernighan's awk <13>: Escape Sequences. (line 124) +* Brian Kernighan's awk: When. (line 21) * Brian Kernighan's awk, extensions: BTL. (line 6) * Brian Kernighan's awk, source code: Other Versions. (line 13) * Brini, Davide: Signature Program. (line 6) +* Brink, Jeroen: DOS Quoting. (line 10) * Broder, Alan J.: Contributors. (line 88) * Brown, Martin: Contributors. (line 82) -* BSD-based operating systems: Glossary. (line 616) +* BSD-based operating systems: Glossary. (line 611) * bt debugger command (alias for backtrace): Execution Stack. (line 13) -* Buening, Andreas <1>: Bugs. (line 70) +* Buening, Andreas <1>: Bugs. (line 71) * Buening, Andreas <2>: Contributors. (line 92) * Buening, Andreas: Acknowledgments. (line 60) -* buffering, input/output <1>: Two-way I/O. (line 70) -* buffering, input/output: I/O Functions. (line 137) -* buffering, interactive vs. noninteractive: I/O Functions. (line 106) -* buffers, flushing: I/O Functions. (line 29) +* buffering, input/output <1>: Two-way I/O. (line 52) +* buffering, input/output: I/O Functions. (line 140) +* buffering, interactive vs. noninteractive: I/O Functions. (line 109) +* buffers, flushing: I/O Functions. (line 32) * buffers, operators for: GNU Regexp Operators. (line 48) * bug reports, email address, bug-gawk@gnu.org: Bugs. (line 30) @@ -30690,6 +31689,7 @@ Index * built-in variables, conveying information: Auto-set. (line 6) * built-in variables, user-modifiable: User-modified. (line 6) * Busybox Awk: Other Versions. (line 88) +* c.e., See common extensions: Conventions. (line 51) * call by reference: Pass By Value/Reference. (line 47) * call by value: Pass By Value/Reference. @@ -30697,30 +31697,29 @@ Index * call stack, display in debugger: Execution Stack. (line 13) * caret (^), ^ operator: Precedence. (line 49) * caret (^), ^= operator <1>: Precedence. (line 95) -* caret (^), ^= operator: Assignment Ops. (line 129) +* caret (^), ^= operator: Assignment Ops. (line 130) * caret (^), in bracket expressions: Bracket Expressions. (line 17) * caret (^), regexp operator <1>: GNU Regexp Operators. (line 59) * caret (^), regexp operator: Regexp Operators. (line 22) * case keyword: Switch Statement. (line 6) -* case sensitivity, and regexps: User-modified. (line 82) -* case sensitivity, and string comparisons: User-modified. (line 82) -* case sensitivity, array indices and: Array Intro. (line 91) +* case sensitivity, and regexps: User-modified. (line 76) +* case sensitivity, and string comparisons: User-modified. (line 76) +* case sensitivity, array indices and: Array Intro. (line 94) * case sensitivity, converting case: String Functions. (line 520) * case sensitivity, example programs: Library Functions. (line 53) * case sensitivity, gawk: Case-sensitivity. (line 26) * case sensitivity, regexps and: Case-sensitivity. (line 6) * CGI, awk scripts for: Options. (line 125) -* changing precision of a number: Changing Precision. (line 6) * character classes, See bracket expressions: Regexp Operators. - (line 55) + (line 56) * character lists in regular expression: Bracket Expressions. (line 6) -* character lists, See bracket expressions: Regexp Operators. (line 55) +* character lists, See bracket expressions: Regexp Operators. (line 56) * character sets (machine character encodings) <1>: Glossary. (line 133) * character sets (machine character encodings): Ordinal Functions. (line 45) * character sets, See Also bracket expressions: Regexp Operators. - (line 55) + (line 56) * characters, counting: Wc Program. (line 6) * characters, transliterating: Translate Program. (line 6) * characters, values of as numbers: Ordinal Functions. (line 6) @@ -30743,23 +31742,23 @@ Index * close() function, portability: Close Files And Pipes. (line 81) * close() function, return value: Close Files And Pipes. - (line 130) -* close() function, two-way pipes and: Two-way I/O. (line 77) + (line 131) +* close() function, two-way pipes and: Two-way I/O. (line 59) * Close, Diane <1>: Contributors. (line 20) -* Close, Diane: Manual History. (line 41) +* Close, Diane: Manual History. (line 34) * Collado, Manuel: Acknowledgments. (line 60) -* collating elements: Bracket Expressions. (line 69) -* collating symbols: Bracket Expressions. (line 76) -* Colombo, Antonio <1>: Contributors. (line 135) +* collating elements: Bracket Expressions. (line 79) +* collating symbols: Bracket Expressions. (line 86) +* Colombo, Antonio <1>: Contributors. (line 137) * Colombo, Antonio: Acknowledgments. (line 60) * columns, aligning: Print Examples. (line 70) * columns, cutting: Cut Program. (line 6) * comma (,), in range patterns: Ranges. (line 6) * command completion, in debugger: Readline Support. (line 6) * command line, arguments <1>: ARGC and ARGV. (line 6) -* command line, arguments <2>: Auto-set. (line 11) +* command line, arguments <2>: Auto-set. (line 15) * command line, arguments: Other Arguments. (line 6) -* command line, directories on: Command line directories. +* command line, directories on: Command-line directories. (line 6) * command line, formats: Running gawk. (line 12) * command line, FS on, setting: Command Line Field Separator. @@ -30778,20 +31777,20 @@ Index * commenting: Comments. (line 6) * commenting, backslash continuation and: Statements/Lines. (line 76) * common extensions, ** operator: Arithmetic Ops. (line 30) -* common extensions, **= operator: Assignment Ops. (line 136) +* common extensions, **= operator: Assignment Ops. (line 137) * common extensions, /dev/stderr special file: Special FD. (line 46) * common extensions, /dev/stdin special file: Special FD. (line 46) * common extensions, /dev/stdout special file: Special FD. (line 46) * common extensions, \x escape sequence: Escape Sequences. (line 61) * common extensions, BINMODE variable: PC Using. (line 33) * common extensions, delete to delete entire arrays: Delete. (line 39) -* common extensions, func keyword: Definition Syntax. (line 83) +* common extensions, func keyword: Definition Syntax. (line 93) * common extensions, length() applied to an array: String Functions. - (line 194) -* common extensions, RS as a regexp: Records. (line 135) + (line 197) +* common extensions, RS as a regexp: gawk split records. (line 6) * common extensions, single character fields: Single Character Fields. (line 6) -* comp.lang.awk newsgroup: Bugs. (line 38) +* comp.lang.awk newsgroup: Bugs. (line 39) * comparison expressions: Typing and Comparison. (line 9) * comparison expressions, as patterns: Expression Patterns. (line 14) @@ -30827,35 +31826,31 @@ Index * configuration options, gawk: Additional Configuration Options. (line 6) * constant regexps: Regexp Usage. (line 57) -* constants, floating-point: Floating-point Constants. - (line 6) * constants, nondecimal: Nondecimal Data. (line 6) * constants, numeric: Scalar Constants. (line 6) * constants, types of: Constants. (line 6) -* context, floating-point: Floating-point Context. - (line 6) * continue program, in debugger: Debugger Execution Control. (line 33) * continue statement: Continue Statement. (line 6) * control statements: Statements. (line 6) * controlling array scanning order: Controlling Scanning. - (line 12) + (line 14) * convert string to lower case: String Functions. (line 521) -* convert string to number: String Functions. (line 385) +* convert string to number: String Functions. (line 388) * convert string to upper case: String Functions. (line 527) * converting integer array subscripts: Numeric Array Subscripts. (line 31) * converting, dates to timestamps: Time Functions. (line 76) * converting, numbers to strings <1>: Bitwise Functions. (line 109) -* converting, numbers to strings: Conversion. (line 6) +* converting, numbers to strings: Strings And Numbers. (line 6) * converting, strings to numbers <1>: Bitwise Functions. (line 109) -* converting, strings to numbers: Conversion. (line 6) -* CONVFMT variable <1>: User-modified. (line 28) -* CONVFMT variable: Conversion. (line 29) +* converting, strings to numbers: Strings And Numbers. (line 6) +* CONVFMT variable <1>: User-modified. (line 30) +* CONVFMT variable: Strings And Numbers. (line 29) * CONVFMT variable, and array subscripts: Numeric Array Subscripts. (line 6) * cookie: Glossary. (line 149) -* coprocesses <1>: Two-way I/O. (line 44) +* coprocesses <1>: Two-way I/O. (line 25) * coprocesses: Redirection. (line 102) * coprocesses, closing: Close Files And Pipes. (line 6) @@ -30864,10 +31859,10 @@ Index * cosine: Numeric Functions. (line 15) * counting: Wc Program. (line 6) * csh utility: Statements/Lines. (line 44) -* csh utility, POSIXLY_CORRECT environment variable: Options. (line 348) -* csh utility, |& operator, comparison with: Two-way I/O. (line 44) -* ctime() user-defined function: Function Example. (line 73) -* currency symbols, localization: Explaining gettext. (line 103) +* csh utility, POSIXLY_CORRECT environment variable: Options. (line 351) +* csh utility, |& operator, comparison with: Two-way I/O. (line 25) +* ctime() user-defined function: Function Example. (line 74) +* currency symbols, localization: Explaining gettext. (line 104) * current system time: Time Functions. (line 66) * custom.h file: Configuration Philosophy. (line 30) @@ -30877,61 +31872,63 @@ Index * cut utility: Cut Program. (line 6) * cut.awk program: Cut Program. (line 45) * d debugger command (alias for delete): Breakpoint Control. (line 64) -* d.c., See dark corner: Conventions. (line 38) -* dark corner <1>: Glossary. (line 189) -* dark corner: Conventions. (line 38) +* d.c., See dark corner: Conventions. (line 42) +* dark corner <1>: Glossary. (line 188) +* dark corner: Conventions. (line 42) * dark corner, "0" is actually true: Truth Values. (line 24) * dark corner, /= operator vs. /=.../ regexp constant: Assignment Ops. - (line 147) + (line 148) * dark corner, ^, in FS: Regexp Field Splitting. (line 59) * dark corner, array subscripts: Uninitialized Subscripts. (line 43) * dark corner, break statement: Break Statement. (line 51) * dark corner, close() function: Close Files And Pipes. - (line 130) + (line 131) * dark corner, command-line arguments: Assignment Options. (line 43) -* dark corner, continue statement: Continue Statement. (line 43) -* dark corner, CONVFMT variable: Conversion. (line 40) -* dark corner, escape sequences: Other Arguments. (line 31) +* dark corner, continue statement: Continue Statement. (line 44) +* dark corner, CONVFMT variable: Strings And Numbers. (line 40) +* dark corner, escape sequences: Other Arguments. (line 35) * dark corner, escape sequences, for metacharacters: Escape Sequences. - (line 134) + (line 142) * dark corner, exit statement: Exit Statement. (line 30) * dark corner, field separators: Field Splitting Summary. (line 46) -* dark corner, FILENAME variable <1>: Auto-set. (line 102) +* dark corner, FILENAME variable <1>: Auto-set. (line 98) * dark corner, FILENAME variable: Getline Notes. (line 19) -* dark corner, FNR/NR variables: Auto-set. (line 323) +* dark corner, FNR/NR variables: Auto-set. (line 316) * dark corner, format-control characters: Control Letters. (line 18) * dark corner, FS as null string: Single Character Fields. (line 20) -* dark corner, input files: Records. (line 118) +* dark corner, input files: awk split records. (line 110) * dark corner, invoking awk: Command Line. (line 16) -* dark corner, length() function: String Functions. (line 180) -* dark corner, locale's decimal point character: Conversion. (line 77) +* dark corner, length() function: String Functions. (line 183) +* dark corner, locale's decimal point character: Locale influences conversions. + (line 17) * dark corner, multiline records: Multiple Line. (line 35) * dark corner, NF variable, decrementing: Changing Fields. (line 107) * dark corner, OFMT variable: OFMT. (line 27) * dark corner, regexp constants: Using Constant Regexps. (line 6) * dark corner, regexp constants, /= operator and: Assignment Ops. - (line 147) + (line 148) * dark corner, regexp constants, as arguments to user-defined functions: Using Constant Regexps. (line 43) * dark corner, split() function: String Functions. (line 359) -* dark corner, strings, storing: Records. (line 210) -* dark corner, value of ARGV[0]: Auto-set. (line 35) +* dark corner, strings, storing: gawk split records. (line 83) +* dark corner, value of ARGV[0]: Auto-set. (line 39) * data, fixed-width: Constant Size. (line 10) * data-driven languages: Basic High Level. (line 85) * database, group, reading: Group Functions. (line 6) * database, users, reading: Passwd Functions. (line 6) * date utility, GNU: Time Functions. (line 17) -* date utility, POSIX: Time Functions. (line 263) +* date utility, POSIX: Time Functions. (line 254) * dates, converting to timestamps: Time Functions. (line 76) * dates, information related to, localization: Explaining gettext. - (line 115) + (line 112) * Davies, Stephen <1>: Contributors. (line 74) * Davies, Stephen: Acknowledgments. (line 60) +* Day, Robert P.J.: Acknowledgments. (line 76) * dcgettext <1>: Programmer i18n. (line 19) * dcgettext: I18N Functions. (line 22) * dcgettext() function (gawk), portability and: I18N Portability. @@ -30940,7 +31937,7 @@ Index * dcngettext: I18N Functions. (line 28) * dcngettext() function (gawk), portability and: I18N Portability. (line 33) -* deadlocks: Two-way I/O. (line 70) +* deadlocks: Two-way I/O. (line 52) * debugger commands, b (break): Breakpoint Control. (line 11) * debugger commands, backtrace: Execution Stack. (line 13) * debugger commands, break: Breakpoint Control. (line 11) @@ -31032,7 +32029,7 @@ Index (line 83) * debugger commands, unwatch: Viewing And Changing Data. (line 84) -* debugger commands, up: Execution Stack. (line 33) +* debugger commands, up: Execution Stack. (line 34) * debugger commands, w (watch): Viewing And Changing Data. (line 67) * debugger commands, watch: Viewing And Changing Data. @@ -31046,10 +32043,10 @@ Index * debugger, read commands from a file: Debugger Info. (line 96) * debugging awk programs: Debugger. (line 6) * debugging gawk, bug reports: Bugs. (line 9) -* decimal point character, locale specific: Options. (line 263) +* decimal point character, locale specific: Options. (line 268) * decrement operators: Increment Ops. (line 35) * default keyword: Switch Statement. (line 6) -* Deifik, Scott <1>: Bugs. (line 70) +* Deifik, Scott <1>: Bugs. (line 71) * Deifik, Scott <2>: Contributors. (line 53) * Deifik, Scott: Acknowledgments. (line 60) * delete ARRAY: Delete. (line 39) @@ -31063,10 +32060,10 @@ Index * deleting entire arrays: Delete. (line 39) * Demaille, Akim: Acknowledgments. (line 60) * describe call stack frame, in debugger: Debugger Info. (line 27) -* differences between gawk and awk: String Functions. (line 194) +* differences between gawk and awk: String Functions. (line 197) * differences in awk and gawk, ARGC/ARGV variables: ARGC and ARGV. - (line 88) -* differences in awk and gawk, ARGIND variable: Auto-set. (line 40) + (line 90) +* differences in awk and gawk, ARGIND variable: Auto-set. (line 44) * differences in awk and gawk, array elements, deleting: Delete. (line 39) * differences in awk and gawk, AWKLIBPATH environment variable: AWKLIBPATH Variable. @@ -31080,22 +32077,22 @@ Index * differences in awk and gawk, BINMODE variable <1>: PC Using. (line 33) * differences in awk and gawk, BINMODE variable: User-modified. - (line 23) + (line 15) * differences in awk and gawk, close() function: Close Files And Pipes. (line 81) -* differences in awk and gawk, command line directories: Command line directories. +* differences in awk and gawk, command-line directories: Command-line directories. (line 6) * differences in awk and gawk, ERRNO variable: Auto-set. (line 82) * differences in awk and gawk, error messages: Special FD. (line 16) * differences in awk and gawk, FIELDWIDTHS variable: User-modified. - (line 35) -* differences in awk and gawk, FPAT variable: User-modified. (line 45) -* differences in awk and gawk, FUNCTAB variable: Auto-set. (line 128) + (line 37) +* differences in awk and gawk, FPAT variable: User-modified. (line 43) +* differences in awk and gawk, FUNCTAB variable: Auto-set. (line 123) * differences in awk and gawk, function arguments (gawk): Calling Built-in. (line 16) * differences in awk and gawk, getline command: Getline. (line 19) * differences in awk and gawk, IGNORECASE variable: User-modified. - (line 82) + (line 76) * differences in awk and gawk, implementation limitations <1>: Redirection. (line 135) * differences in awk and gawk, implementation limitations: Getline Notes. @@ -31108,34 +32105,38 @@ Index (line 6) * differences in awk and gawk, line continuations: Conditional Exp. (line 34) -* differences in awk and gawk, LINT variable: User-modified. (line 98) +* differences in awk and gawk, LINT variable: User-modified. (line 88) * differences in awk and gawk, match() function: String Functions. - (line 257) + (line 260) * differences in awk and gawk, print/printf statements: Format Modifiers. (line 13) -* differences in awk and gawk, PROCINFO array: Auto-set. (line 142) -* differences in awk and gawk, record separators: Records. (line 132) +* differences in awk and gawk, PROCINFO array: Auto-set. (line 137) +* differences in awk and gawk, read timeouts: Read Timeout. (line 6) +* differences in awk and gawk, record separators: awk split records. + (line 124) * differences in awk and gawk, regexp constants: Using Constant Regexps. (line 43) * differences in awk and gawk, regular expressions: Case-sensitivity. (line 26) -* differences in awk and gawk, RS/RT variables: Records. (line 187) -* differences in awk and gawk, RT variable: Auto-set. (line 275) +* differences in awk and gawk, RS/RT variables: gawk split records. + (line 58) +* differences in awk and gawk, RT variable: Auto-set. (line 272) * differences in awk and gawk, single-character fields: Single Character Fields. (line 6) * differences in awk and gawk, split() function: String Functions. (line 347) * differences in awk and gawk, strings: Scalar Constants. (line 20) -* differences in awk and gawk, strings, storing: Records. (line 206) -* differences in awk and gawk, SYMTAB variable: Auto-set. (line 283) +* differences in awk and gawk, strings, storing: gawk split records. + (line 77) +* differences in awk and gawk, SYMTAB variable: Auto-set. (line 276) * differences in awk and gawk, TEXTDOMAIN variable: User-modified. - (line 162) + (line 152) * differences in awk and gawk, trunc-mod operation: Arithmetic Ops. (line 66) -* directories, command line: Command line directories. +* directories, command-line: Command-line directories. (line 6) -* directories, searching: Igawk Program. (line 368) -* directories, searching for shared libraries: AWKLIBPATH Variable. +* directories, searching: Programs Exercises. (line 70) +* directories, searching for loadable extensions: AWKLIBPATH Variable. (line 6) * directories, searching for source files: AWKPATH Variable. (line 6) * disable breakpoint: Breakpoint Control. (line 69) @@ -31143,6 +32144,7 @@ Index * display debugger command: Viewing And Changing Data. (line 8) * display debugger options: Debugger Info. (line 57) +* div: Numeric Functions. (line 18) * division: Arithmetic Ops. (line 44) * do-while statement: Do Statement. (line 6) * do-while statement, use of regexps in: Regexp Usage. (line 19) @@ -31154,10 +32156,8 @@ Index * dollar sign ($), incrementing fields and arrays: Increment Ops. (line 30) * dollar sign ($), regexp operator: Regexp Operators. (line 35) -* double precision floating-point: General Arithmetic. (line 21) -* double quote (") in shell commands: Read Terminal. (line 25) -* double quote ("), in regexp constants: Computed Regexps. (line 28) -* double quote ("), in shell commands: Quoting. (line 37) +* double quote ("), in regexp constants: Computed Regexps. (line 29) +* double quote ("), in shell commands: Quoting. (line 54) * down debugger command: Execution Stack. (line 21) * Drepper, Ulrich: Acknowledgments. (line 52) * dump all variables of a program: Options. (line 93) @@ -31168,10 +32168,10 @@ Index * dynamically loaded extensions: Dynamic Extensions. (line 6) * e debugger command (alias for enable): Breakpoint Control. (line 73) * EBCDIC: Ordinal Functions. (line 45) -* effective group ID of gawk user: Auto-set. (line 147) -* effective user ID of gawk user: Auto-set. (line 151) +* effective group ID of gawk user: Auto-set. (line 142) +* effective user ID of gawk user: Auto-set. (line 146) * egrep utility <1>: Egrep Program. (line 6) -* egrep utility: Bracket Expressions. (line 24) +* egrep utility: Bracket Expressions. (line 26) * egrep.awk program: Egrep Program. (line 54) * elements in arrays, assigning values: Assigning Elements. (line 6) * elements in arrays, deleting: Delete. (line 6) @@ -31185,7 +32185,7 @@ Index * empty array elements: Reference to Elements. (line 18) * empty pattern: Empty. (line 6) -* empty strings: Records. (line 122) +* empty strings: awk split records. (line 114) * empty strings, See null strings: Regexp Field Splitting. (line 43) * enable breakpoint: Breakpoint Control. (line 73) @@ -31197,37 +32197,37 @@ Index * END pattern, and profiling: Profiling. (line 62) * END pattern, assert() user-defined function and: Assert Function. (line 75) -* END pattern, backslash continuation and: Egrep Program. (line 220) * END pattern, Boolean patterns and: Expression Patterns. (line 70) * END pattern, exit statement and: Exit Statement. (line 12) * END pattern, next/nextfile statements and <1>: Next Statement. - (line 45) + (line 44) * END pattern, next/nextfile statements and: I/O And BEGIN/END. - (line 37) + (line 36) * END pattern, operators and: Using BEGIN/END. (line 17) * END pattern, print statement and: I/O And BEGIN/END. (line 16) * ENDFILE pattern: BEGINFILE/ENDFILE. (line 6) * ENDFILE pattern, Boolean patterns and: Expression Patterns. (line 70) * endfile() user-defined function: Filetrans Function. (line 62) -* endgrent() function (C library): Group Functions. (line 215) -* endgrent() user-defined function: Group Functions. (line 218) +* endgrent() function (C library): Group Functions. (line 212) +* endgrent() user-defined function: Group Functions. (line 215) * endpwent() function (C library): Passwd Functions. (line 210) * endpwent() user-defined function: Passwd Functions. (line 213) +* English, Steve: Advanced Features. (line 6) * ENVIRON array: Auto-set. (line 60) * environment variables used by gawk: Environment Variables. (line 6) * environment variables, in ENVIRON array: Auto-set. (line 60) -* epoch, definition of: Glossary. (line 235) +* epoch, definition of: Glossary. (line 234) * equals sign (=), = operator: Assignment Ops. (line 6) * equals sign (=), == operator <1>: Precedence. (line 65) * equals sign (=), == operator: Comparison Operators. (line 11) -* EREs (Extended Regular Expressions): Bracket Expressions. (line 24) +* EREs (Extended Regular Expressions): Bracket Expressions. (line 26) * ERRNO variable <1>: TCP/IP Networking. (line 54) * ERRNO variable: Auto-set. (line 82) * ERRNO variable, with BEGINFILE pattern: BEGINFILE/ENDFILE. (line 26) * ERRNO variable, with close() function: Close Files And Pipes. - (line 138) + (line 139) * ERRNO variable, with getline command: Getline. (line 19) * error handling: Special FD. (line 16) * error handling, ERRNO variable and: Auto-set. (line 82) @@ -31243,7 +32243,7 @@ Index * evaluation order, concatenation: Concatenation. (line 41) * evaluation order, functions: Calling Built-in. (line 30) * examining fields: Fields. (line 6) -* exclamation point (!), ! operator <1>: Egrep Program. (line 170) +* exclamation point (!), ! operator <1>: Egrep Program. (line 175) * exclamation point (!), ! operator <2>: Precedence. (line 52) * exclamation point (!), ! operator: Boolean Ops. (line 67) * exclamation point (!), != operator <1>: Precedence. (line 65) @@ -31255,18 +32255,18 @@ Index * exclamation point (!), !~ operator <3>: Comparison Operators. (line 11) * exclamation point (!), !~ operator <4>: Regexp Constants. (line 6) -* exclamation point (!), !~ operator <5>: Computed Regexps. (line 6) -* exclamation point (!), !~ operator <6>: Case-sensitivity. (line 26) +* exclamation point (!), !~ operator <5>: Case-sensitivity. (line 26) +* exclamation point (!), !~ operator <6>: Computed Regexps. (line 6) * exclamation point (!), !~ operator: Regexp Usage. (line 19) * exit statement: Exit Statement. (line 6) * exit status, of gawk: Exit Status. (line 6) * exit status, of VMS: VMS Running. (line 29) * exit the debugger: Miscellaneous Debugger Commands. (line 99) -* exp: Numeric Functions. (line 18) -* expand utility: Very Simple. (line 69) +* exp: Numeric Functions. (line 33) +* expand utility: Very Simple. (line 72) * Expat XML parser library: gawkextlib. (line 35) -* exponent: Numeric Functions. (line 18) +* exponent: Numeric Functions. (line 33) * expressions: Expressions. (line 6) * expressions, as patterns: Expression Patterns. (line 6) * expressions, assignment: Assignment Ops. (line 6) @@ -31277,14 +32277,14 @@ Index * expressions, matching, See comparison expressions: Typing and Comparison. (line 9) * expressions, selecting: Conditional Exp. (line 6) -* Extended Regular Expressions (EREs): Bracket Expressions. (line 24) +* Extended Regular Expressions (EREs): Bracket Expressions. (line 26) * extension API: Extension API Description. (line 6) * extension API informational variables: Extension API Informational Variables. (line 6) * extension API version: Extension Versioning. (line 6) -* extension API, version number: Auto-set. (line 238) +* extension API, version number: Auto-set. (line 239) * extension example: Extension Example. (line 6) * extension registration: Registration Functions. (line 6) @@ -31295,21 +32295,23 @@ Index * extensions, Brian Kernighan's awk <1>: Common Extensions. (line 6) * extensions, Brian Kernighan's awk: BTL. (line 6) * extensions, common, ** operator: Arithmetic Ops. (line 30) -* extensions, common, **= operator: Assignment Ops. (line 136) +* extensions, common, **= operator: Assignment Ops. (line 137) * extensions, common, /dev/stderr special file: Special FD. (line 46) * extensions, common, /dev/stdin special file: Special FD. (line 46) * extensions, common, /dev/stdout special file: Special FD. (line 46) * extensions, common, \x escape sequence: Escape Sequences. (line 61) * extensions, common, BINMODE variable: PC Using. (line 33) * extensions, common, delete to delete entire arrays: Delete. (line 39) -* extensions, common, fflush() function: I/O Functions. (line 40) -* extensions, common, func keyword: Definition Syntax. (line 83) +* extensions, common, fflush() function: I/O Functions. (line 43) +* extensions, common, func keyword: Definition Syntax. (line 93) * extensions, common, length() applied to an array: String Functions. - (line 194) -* extensions, common, RS as a regexp: Records. (line 135) + (line 197) +* extensions, common, RS as a regexp: gawk split records. (line 6) * extensions, common, single character fields: Single Character Fields. (line 6) * extensions, in gawk, not in POSIX awk: POSIX/GNU. (line 6) +* extensions, loading, @load directive: Loading Shared Libraries. + (line 8) * extensions, mawk: Common Extensions. (line 6) * extensions, where to find: gawkextlib. (line 6) * extract.awk program: Extract Program. (line 79) @@ -31320,12 +32322,11 @@ Index * FDL (Free Documentation License): GNU Free Documentation License. (line 7) * features, adding to gawk: Adding Code. (line 6) -* features, advanced, See advanced features: Obsolete. (line 6) * features, deprecated: Obsolete. (line 6) * features, undocumented: Undocumented. (line 6) * Fenlason, Jay <1>: Contributors. (line 18) * Fenlason, Jay: History. (line 30) -* fflush: I/O Functions. (line 25) +* fflush: I/O Functions. (line 28) * field numbers: Nonconstant Fields. (line 6) * field operator $: Fields. (line 19) * field operators, dollar sign as: Fields. (line 19) @@ -31334,17 +32335,17 @@ Index (line 6) * field separator, POSIX and: Field Splitting Summary. (line 40) -* field separators <1>: User-modified. (line 56) +* field separators <1>: User-modified. (line 50) * field separators: Field Separators. (line 15) * field separators, choice of: Field Separators. (line 51) -* field separators, FIELDWIDTHS variable and: User-modified. (line 35) -* field separators, FPAT variable and: User-modified. (line 45) +* field separators, FIELDWIDTHS variable and: User-modified. (line 37) +* field separators, FPAT variable and: User-modified. (line 43) * field separators, POSIX and: Fields. (line 6) * field separators, regular expressions as <1>: Regexp Field Splitting. (line 6) * field separators, regular expressions as: Field Separators. (line 51) * field separators, See Also OFS: Changing Fields. (line 64) -* field separators, spaces as: Cut Program. (line 109) +* field separators, spaces as: Cut Program. (line 108) * fields <1>: Basic High Level. (line 73) * fields <2>: Fields. (line 6) * fields: Reading Files. (line 14) @@ -31358,24 +32359,25 @@ Index * fields, separating: Field Separators. (line 15) * fields, single-character: Single Character Fields. (line 6) -* FIELDWIDTHS variable <1>: User-modified. (line 35) +* FIELDWIDTHS variable <1>: User-modified. (line 37) * FIELDWIDTHS variable: Constant Size. (line 23) * file descriptors: Special FD. (line 6) -* file names, distinguishing: Auto-set. (line 52) +* file inclusion, @include directive: Include Files. (line 8) +* file names, distinguishing: Auto-set. (line 56) * file names, in compatibility mode: Special Caveats. (line 9) * file names, standard streams in gawk: Special FD. (line 46) -* FILENAME variable <1>: Auto-set. (line 102) +* FILENAME variable <1>: Auto-set. (line 98) * FILENAME variable: Reading Files. (line 6) * FILENAME variable, getline, setting with: Getline Notes. (line 19) * filenames, assignments as: Ignoring Assigns. (line 6) -* files, .gmo: Explaining gettext. (line 41) -* files, .gmo, converting from .po: I18N Example. (line 62) +* files, .gmo: Explaining gettext. (line 42) * files, .gmo, specifying directory of <1>: Programmer i18n. (line 47) -* files, .gmo, specifying directory of: Explaining gettext. (line 53) +* files, .gmo, specifying directory of: Explaining gettext. (line 54) +* files, .mo, converting from .po: I18N Example. (line 63) * files, .po <1>: Translator i18n. (line 6) -* files, .po: Explaining gettext. (line 36) -* files, .po, converting to .gmo: I18N Example. (line 62) -* files, .pot: Explaining gettext. (line 30) +* files, .po: Explaining gettext. (line 37) +* files, .po, converting to .mo: I18N Example. (line 63) +* files, .pot: Explaining gettext. (line 31) * files, /dev/... special files: Special FD. (line 46) * files, /inet/... (gawk): TCP/IP Networking. (line 6) * files, /inet4/... (gawk): TCP/IP Networking. (line 6) @@ -31392,33 +32394,33 @@ Index * files, managing: Data File Management. (line 6) * files, managing, data file boundaries: Filetrans Function. (line 6) -* files, message object: Explaining gettext. (line 41) +* files, message object: Explaining gettext. (line 42) * files, message object, converting from portable object files: I18N Example. - (line 62) + (line 63) * files, message object, specifying directory of <1>: Programmer i18n. (line 47) * files, message object, specifying directory of: Explaining gettext. - (line 53) -* files, multiple passes over: Other Arguments. (line 49) + (line 54) +* files, multiple passes over: Other Arguments. (line 53) * files, multiple, duplicating output into: Tee Program. (line 6) * files, output, See output files: Close Files And Pipes. (line 6) * files, password: Passwd Functions. (line 16) * files, portable object <1>: Translator i18n. (line 6) -* files, portable object: Explaining gettext. (line 36) -* files, portable object template: Explaining gettext. (line 30) +* files, portable object: Explaining gettext. (line 37) +* files, portable object template: Explaining gettext. (line 31) * files, portable object, converting to message object files: I18N Example. - (line 62) + (line 63) * files, portable object, generating: Options. (line 147) -* files, processing, ARGIND variable and: Auto-set. (line 47) +* files, processing, ARGIND variable and: Auto-set. (line 51) * files, reading: Rewind Function. (line 6) * files, reading, multiline records: Multiple Line. (line 6) * files, searching for regular expressions: Egrep Program. (line 6) * files, skipping: File Checking. (line 6) -* files, source, search path for: Igawk Program. (line 368) +* files, source, search path for: Programs Exercises. (line 70) * files, splitting: Split Program. (line 6) * files, Texinfo, extracting programs from: Extract Program. (line 6) -* find substring in string: String Functions. (line 151) +* find substring in string: String Functions. (line 155) * finding extensions: Finding Extensions. (line 6) * finish debugger command: Debugger Execution Control. (line 39) @@ -31426,17 +32428,15 @@ Index * fixed-width data: Constant Size. (line 10) * flag variables <1>: Tee Program. (line 20) * flag variables: Boolean Ops. (line 67) -* floating-point, numbers <1>: Unexpected Results. (line 6) -* floating-point, numbers: General Arithmetic. (line 6) * floating-point, numbers, arbitrary precision: Arbitrary Precision Arithmetic. (line 6) * floating-point, VAX/VMS: VMS Running. (line 51) -* flush buffered output: I/O Functions. (line 25) +* flush buffered output: I/O Functions. (line 28) * fnmatch() extension function: Extension Sample Fnmatch. (line 12) -* FNR variable <1>: Auto-set. (line 112) +* FNR variable <1>: Auto-set. (line 107) * FNR variable: Records. (line 6) -* FNR variable, changing: Auto-set. (line 323) +* FNR variable, changing: Auto-set. (line 316) * for statement: For Statement. (line 6) * for statement, looping over arrays: Scanning an Array. (line 20) * fork() extension function: Extension Sample Fork. @@ -31450,30 +32450,30 @@ Index * format time string: Time Functions. (line 48) * formats, numeric output: OFMT. (line 6) * formatting output: Printf. (line 6) -* formatting strings: String Functions. (line 378) +* formatting strings: String Functions. (line 381) * forward slash (/) to enclose regular expressions: Regexp. (line 10) * forward slash (/), / operator: Precedence. (line 55) * forward slash (/), /= operator <1>: Precedence. (line 95) -* forward slash (/), /= operator: Assignment Ops. (line 129) +* forward slash (/), /= operator: Assignment Ops. (line 130) * forward slash (/), /= operator, vs. /=.../ regexp constant: Assignment Ops. - (line 147) + (line 148) * forward slash (/), patterns and: Expression Patterns. (line 24) -* FPAT variable <1>: User-modified. (line 45) +* FPAT variable <1>: User-modified. (line 43) * FPAT variable: Splitting By Content. (line 27) * frame debugger command: Execution Stack. (line 25) * Free Documentation License (FDL): GNU Free Documentation License. (line 7) -* Free Software Foundation (FSF) <1>: Glossary. (line 297) +* Free Software Foundation (FSF) <1>: Glossary. (line 296) * Free Software Foundation (FSF) <2>: Getting. (line 10) * Free Software Foundation (FSF): Manual History. (line 6) -* FreeBSD: Glossary. (line 616) -* FS variable <1>: User-modified. (line 56) +* FreeBSD: Glossary. (line 611) +* FS variable <1>: User-modified. (line 50) * FS variable: Field Separators. (line 15) * FS variable, --field-separator option and: Options. (line 21) * FS variable, as null string: Single Character Fields. (line 20) -* FS variable, as TAB character: Options. (line 259) +* FS variable, as TAB character: Options. (line 264) * FS variable, changing value of: Field Separators. (line 35) * FS variable, running awk programs and: Cut Program. (line 68) * FS variable, setting from command line: Command Line Field Separator. @@ -31481,14 +32481,15 @@ Index * FS, containing ^: Regexp Field Splitting. (line 59) * FS, in multiline records: Multiple Line. (line 41) -* FSF (Free Software Foundation) <1>: Glossary. (line 297) +* FSF (Free Software Foundation) <1>: Glossary. (line 296) * FSF (Free Software Foundation) <2>: Getting. (line 10) * FSF (Free Software Foundation): Manual History. (line 6) * fts() extension function: Extension Sample File Functions. - (line 77) -* FUNCTAB array: Auto-set. (line 128) + (line 61) +* FUNCTAB array: Auto-set. (line 123) * function calls: Function Calls. (line 6) * function calls, indirect: Indirect Calls. (line 6) +* function calls, indirect, @-notation for: Indirect Calls. (line 47) * function definition example: Function Example. (line 6) * function pointers: Indirect Calls. (line 6) * functions, arrays as parameters to: Pass By Value/Reference. @@ -31496,7 +32497,7 @@ Index * functions, built-in <1>: Functions. (line 6) * functions, built-in: Function Calls. (line 10) * functions, built-in, evaluation order: Calling Built-in. (line 30) -* functions, defining: Definition Syntax. (line 6) +* functions, defining: Definition Syntax. (line 9) * functions, library: Library Functions. (line 6) * functions, library, assertions: Assert Function. (line 6) * functions, library, associative arrays and: Library Names. (line 57) @@ -31519,9 +32520,9 @@ Index * functions, library, rounding numbers: Round Function. (line 6) * functions, library, user database, reading: Passwd Functions. (line 6) -* functions, names of <1>: Definition Syntax. (line 20) +* functions, names of <1>: Definition Syntax. (line 23) * functions, names of: Arrays. (line 18) -* functions, recursive: Definition Syntax. (line 73) +* functions, recursive: Definition Syntax. (line 83) * functions, string-translation: I18N Functions. (line 6) * functions, undefined: Pass By Value/Reference. (line 71) @@ -31532,19 +32533,19 @@ Index * functions, user-defined, next/nextfile statements and <1>: Nextfile Statement. (line 47) * functions, user-defined, next/nextfile statements and: Next Statement. - (line 45) -* G-d: Acknowledgments. (line 78) + (line 44) +* G-d: Acknowledgments. (line 92) * Garfinkle, Scott: Contributors. (line 34) * gawk program, dynamic profiling: Profiling. (line 179) -* gawk version: Auto-set. (line 213) +* gawk version: Auto-set. (line 214) * gawk, ARGIND variable in: Other Arguments. (line 12) * gawk, awk and <1>: This Manual. (line 14) -* gawk, awk and: Preface. (line 23) +* gawk, awk and: Preface. (line 21) * gawk, bitwise operations in: Bitwise Functions. (line 39) * gawk, break statement in: Break Statement. (line 51) * gawk, built-in variables and: Built-in Variables. (line 14) -* gawk, character classes and: Bracket Expressions. (line 90) -* gawk, coding style in: Adding Code. (line 38) +* gawk, character classes and: Bracket Expressions. (line 100) +* gawk, coding style in: Adding Code. (line 39) * gawk, command-line options, and regular expressions: GNU Regexp Operators. (line 70) * gawk, comparison operators and: Comparison Operators. @@ -31553,35 +32554,35 @@ Index (line 6) * gawk, configuring, options: Additional Configuration Options. (line 6) -* gawk, continue statement in: Continue Statement. (line 43) +* gawk, continue statement in: Continue Statement. (line 44) * gawk, distribution: Distribution contents. (line 6) * gawk, ERRNO variable in <1>: TCP/IP Networking. (line 54) * gawk, ERRNO variable in <2>: Auto-set. (line 82) * gawk, ERRNO variable in <3>: BEGINFILE/ENDFILE. (line 26) * gawk, ERRNO variable in <4>: Close Files And Pipes. - (line 138) + (line 139) * gawk, ERRNO variable in: Getline. (line 19) -* gawk, escape sequences: Escape Sequences. (line 124) -* gawk, extensions, disabling: Options. (line 247) +* gawk, escape sequences: Escape Sequences. (line 132) +* gawk, extensions, disabling: Options. (line 252) * gawk, features, adding: Adding Code. (line 6) * gawk, features, advanced: Advanced Features. (line 6) -* gawk, field separators and: User-modified. (line 77) -* gawk, FIELDWIDTHS variable in <1>: User-modified. (line 35) +* gawk, field separators and: User-modified. (line 71) +* gawk, FIELDWIDTHS variable in <1>: User-modified. (line 37) * gawk, FIELDWIDTHS variable in: Constant Size. (line 23) * gawk, file names in: Special Files. (line 6) * gawk, format-control characters: Control Letters. (line 18) -* gawk, FPAT variable in <1>: User-modified. (line 45) +* gawk, FPAT variable in <1>: User-modified. (line 43) * gawk, FPAT variable in: Splitting By Content. (line 27) -* gawk, FUNCTAB array in: Auto-set. (line 128) +* gawk, FUNCTAB array in: Auto-set. (line 123) * gawk, function arguments and: Calling Built-in. (line 16) * gawk, hexadecimal numbers and: Nondecimal-numbers. (line 42) * gawk, IGNORECASE variable in <1>: Array Sorting Functions. (line 83) -* gawk, IGNORECASE variable in <2>: String Functions. (line 48) -* gawk, IGNORECASE variable in <3>: Array Intro. (line 91) -* gawk, IGNORECASE variable in <4>: User-modified. (line 82) +* gawk, IGNORECASE variable in <2>: String Functions. (line 58) +* gawk, IGNORECASE variable in <3>: Array Intro. (line 94) +* gawk, IGNORECASE variable in <4>: User-modified. (line 76) * gawk, IGNORECASE variable in: Case-sensitivity. (line 26) * gawk, implementation issues: Notes. (line 6) * gawk, implementation issues, debugging: Compatibility Mode. (line 6) @@ -31596,16 +32597,16 @@ Index (line 6) * gawk, interval expressions and: Regexp Operators. (line 139) * gawk, line continuation in: Conditional Exp. (line 34) -* gawk, LINT variable in: User-modified. (line 98) +* gawk, LINT variable in: User-modified. (line 88) * gawk, list of contributors to: Contributors. (line 6) * gawk, MS-DOS version of: PC Using. (line 10) * gawk, MS-Windows version of: PC Using. (line 10) * gawk, newlines in: Statements/Lines. (line 12) * gawk, octal numbers and: Nondecimal-numbers. (line 42) -* gawk, OS/2 version of: PC Using. (line 10) -* gawk, PROCINFO array in <1>: Two-way I/O. (line 116) +* gawk, OS/2 version of: PC Using. (line 16) +* gawk, PROCINFO array in <1>: Two-way I/O. (line 99) * gawk, PROCINFO array in <2>: Time Functions. (line 47) -* gawk, PROCINFO array in: Auto-set. (line 142) +* gawk, PROCINFO array in: Auto-set. (line 137) * gawk, regexp constants and: Using Constant Regexps. (line 28) * gawk, regular expressions, case sensitivity: Case-sensitivity. @@ -31613,48 +32614,48 @@ Index * gawk, regular expressions, operators: GNU Regexp Operators. (line 6) * gawk, regular expressions, precedence: Regexp Operators. (line 161) -* gawk, RT variable in <1>: Auto-set. (line 275) +* gawk, RT variable in <1>: Auto-set. (line 272) * gawk, RT variable in <2>: Multiple Line. (line 129) -* gawk, RT variable in: Records. (line 132) -* gawk, See Also awk: Preface. (line 36) +* gawk, RT variable in: awk split records. (line 124) +* gawk, See Also awk: Preface. (line 34) * gawk, source code, obtaining: Getting. (line 6) * gawk, splitting fields and: Constant Size. (line 88) * gawk, string-translation functions: I18N Functions. (line 6) -* gawk, SYMTAB array in: Auto-set. (line 283) -* gawk, TEXTDOMAIN variable in: User-modified. (line 162) +* gawk, SYMTAB array in: Auto-set. (line 276) +* gawk, TEXTDOMAIN variable in: User-modified. (line 152) * gawk, timestamps: Time Functions. (line 6) -* gawk, uses for: Preface. (line 36) -* gawk, versions of, information about, printing: Options. (line 293) +* gawk, uses for: Preface. (line 34) +* gawk, versions of, information about, printing: Options. (line 298) * gawk, VMS version of: VMS Installation. (line 6) * gawk, word-boundary operator: GNU Regexp Operators. (line 63) * gawkextlib: gawkextlib. (line 6) * gawkextlib project: gawkextlib. (line 6) -* General Public License (GPL): Glossary. (line 306) +* General Public License (GPL): Glossary. (line 305) * General Public License, See GPL: Manual History. (line 11) * generate time values: Time Functions. (line 25) -* gensub <1>: String Functions. (line 82) +* gensub <1>: String Functions. (line 89) * gensub: Using Constant Regexps. (line 43) * gensub() function (gawk), escape processing: Gory Details. (line 6) * getaddrinfo() function (C library): TCP/IP Networking. (line 38) * getgrent() function (C library): Group Functions. (line 6) * getgrent() user-defined function: Group Functions. (line 6) -* getgrgid() function (C library): Group Functions. (line 186) -* getgrgid() user-defined function: Group Functions. (line 189) -* getgrnam() function (C library): Group Functions. (line 175) -* getgrnam() user-defined function: Group Functions. (line 180) -* getgruser() function (C library): Group Functions. (line 195) -* getgruser() function, user-defined: Group Functions. (line 198) +* getgrgid() function (C library): Group Functions. (line 183) +* getgrgid() user-defined function: Group Functions. (line 186) +* getgrnam() function (C library): Group Functions. (line 172) +* getgrnam() user-defined function: Group Functions. (line 177) +* getgruser() function (C library): Group Functions. (line 192) +* getgruser() function, user-defined: Group Functions. (line 195) * getline command: Reading Files. (line 20) * getline command, _gr_init() user-defined function: Group Functions. - (line 82) + (line 83) * getline command, _pw_init() function: Passwd Functions. (line 154) * getline command, coprocesses, using from <1>: Close Files And Pipes. (line 6) * getline command, coprocesses, using from: Getline/Coprocess. (line 6) -* getline command, deadlock and: Two-way I/O. (line 70) +* getline command, deadlock and: Two-way I/O. (line 52) * getline command, explicit input with: Getline. (line 6) * getline command, FILENAME variable and: Getline Notes. (line 19) * getline command, return values: Getline. (line 19) @@ -31674,42 +32675,41 @@ Index * getpwuid() function (C library): Passwd Functions. (line 188) * getpwuid() user-defined function: Passwd Functions. (line 192) * gettext library: Explaining gettext. (line 6) -* gettext library, locale categories: Explaining gettext. (line 80) -* gettext() function (C library): Explaining gettext. (line 62) +* gettext library, locale categories: Explaining gettext. (line 81) +* gettext() function (C library): Explaining gettext. (line 63) * gettimeofday() extension function: Extension Sample Time. - (line 13) -* git utility <1>: Adding Code. (line 111) + (line 12) +* git utility <1>: Adding Code. (line 112) * git utility <2>: Accessing The Source. (line 10) * git utility <3>: Other Versions. (line 29) * git utility: gawkextlib. (line 29) -* git, use of for gawk source code: Derived Files. (line 6) -* GMP: Gawk and MPFR. (line 6) +* Git, use of for gawk source code: Derived Files. (line 6) * GNITS mailing list: Acknowledgments. (line 52) -* GNU awk, See gawk: Preface. (line 49) +* GNU awk, See gawk: Preface. (line 51) * GNU Free Documentation License: GNU Free Documentation License. (line 7) -* GNU General Public License: Glossary. (line 306) -* GNU Lesser General Public License: Glossary. (line 397) +* GNU General Public License: Glossary. (line 305) +* GNU Lesser General Public License: Glossary. (line 396) * GNU long options <1>: Options. (line 6) * GNU long options: Command Line. (line 13) * GNU long options, printing list of: Options. (line 154) -* GNU Project <1>: Glossary. (line 315) +* GNU Project <1>: Glossary. (line 314) * GNU Project: Manual History. (line 11) -* GNU/Linux <1>: Glossary. (line 616) +* GNU/Linux <1>: Glossary. (line 611) * GNU/Linux <2>: I18N Example. (line 55) * GNU/Linux: Manual History. (line 28) * Gordon, Assaf: Contributors. (line 105) -* GPL (General Public License) <1>: Glossary. (line 306) +* GPL (General Public License) <1>: Glossary. (line 305) * GPL (General Public License): Manual History. (line 11) * GPL (General Public License), printing: Options. (line 88) * grcat program: Group Functions. (line 16) * Grigera, Juan: Contributors. (line 57) * group database, reading: Group Functions. (line 6) * group file: Group Functions. (line 6) -* group ID of gawk user: Auto-set. (line 186) +* group ID of gawk user: Auto-set. (line 187) * groups, information about: Group Functions. (line 6) -* gsub <1>: String Functions. (line 135) +* gsub <1>: String Functions. (line 139) * gsub: Using Constant Regexps. (line 43) * gsub() function, arguments of: String Functions. (line 460) @@ -31725,7 +32725,7 @@ Index * help debugger command: Miscellaneous Debugger Commands. (line 66) * hexadecimal numbers: Nondecimal-numbers. (line 6) -* hexadecimal values, enabling interpretation of: Options. (line 207) +* hexadecimal values, enabling interpretation of: Options. (line 211) * history expansion, in debugger: Readline Support. (line 6) * histsort.awk program: History Sorting. (line 25) * Hughes, Phil: Acknowledgments. (line 43) @@ -31734,30 +32734,28 @@ Index * hyphen (-), -- operator <1>: Precedence. (line 46) * hyphen (-), -- operator: Increment Ops. (line 48) * hyphen (-), -= operator <1>: Precedence. (line 95) -* hyphen (-), -= operator: Assignment Ops. (line 129) +* hyphen (-), -= operator: Assignment Ops. (line 130) * hyphen (-), filenames beginning with: Options. (line 59) * hyphen (-), in bracket expressions: Bracket Expressions. (line 17) * i debugger command (alias for info): Debugger Info. (line 13) * id utility: Id Program. (line 6) * id.awk program: Id Program. (line 30) -* IEEE-754 format: Floating-point Representation. - (line 6) * if statement: If Statement. (line 6) * if statement, actions, changing: Ranges. (line 25) * if statement, use of regexps in: Regexp Usage. (line 19) * igawk.sh program: Igawk Program. (line 124) * ignore breakpoint: Breakpoint Control. (line 87) * ignore debugger command: Breakpoint Control. (line 87) -* IGNORECASE variable: User-modified. (line 82) -* IGNORECASE variable, and array indices: Array Intro. (line 91) +* IGNORECASE variable: User-modified. (line 76) +* IGNORECASE variable, and array indices: Array Intro. (line 94) * IGNORECASE variable, and array sorting functions: Array Sorting Functions. (line 83) * IGNORECASE variable, in example programs: Library Functions. (line 53) * IGNORECASE variable, with ~ and !~ operators: Case-sensitivity. (line 26) -* Illumos: Other Versions. (line 104) -* Illumos, POSIX-compliant awk: Other Versions. (line 104) +* Illumos: Other Versions. (line 105) +* Illumos, POSIX-compliant awk: Other Versions. (line 105) * implementation issues, gawk: Notes. (line 6) * implementation issues, gawk, debugging: Compatibility Mode. (line 6) * implementation issues, gawk, limits <1>: Redirection. (line 135) @@ -31770,12 +32768,14 @@ Index (line 43) * in operator, order of array access: Scanning an Array. (line 48) * in operator, testing if array element exists: Reference to Elements. - (line 37) + (line 38) * in operator, use in loops: Scanning an Array. (line 17) +* including files, @include directive: Include Files. (line 8) * increment operators: Increment Ops. (line 6) -* index: String Functions. (line 151) -* indexing arrays: Array Intro. (line 49) +* index: String Functions. (line 155) +* indexing arrays: Array Intro. (line 50) * indirect function calls: Indirect Calls. (line 6) +* indirect function calls, @-notation: Indirect Calls. (line 47) * infinite precision: Arbitrary Precision Arithmetic. (line 6) * info debugger command: Debugger Info. (line 13) @@ -31789,9 +32789,9 @@ Index * input files, examples: Sample Data Files. (line 6) * input files, reading: Reading Files. (line 6) * input files, running awk without: Read Terminal. (line 6) -* input files, variable assignments and: Other Arguments. (line 19) +* input files, variable assignments and: Other Arguments. (line 23) * input pipeline: Getline/Pipe. (line 9) -* input record, length of: String Functions. (line 171) +* input record, length of: String Functions. (line 174) * input redirection: Getline/File. (line 6) * input, data, nondecimal: Nondecimal Data. (line 6) * input, explicit: Getline. (line 6) @@ -31801,90 +32801,87 @@ Index * input, standard <1>: Special FD. (line 6) * input, standard: Read Terminal. (line 6) * input/output functions: I/O Functions. (line 6) -* input/output, binary: User-modified. (line 10) +* input/output, binary: User-modified. (line 15) * input/output, from BEGIN and END: I/O And BEGIN/END. (line 6) -* input/output, two-way: Two-way I/O. (line 44) +* input/output, two-way: Two-way I/O. (line 25) * insomnia, cure for: Alarm Program. (line 6) * installation, VMS: VMS Installation. (line 6) * installing gawk: Installation. (line 6) * instruction tracing, in debugger: Debugger Info. (line 89) -* int: Numeric Functions. (line 23) +* int: Numeric Functions. (line 38) * INT signal (MS-Windows): Profiling. (line 214) * integer array indices: Numeric Array Subscripts. (line 31) -* integers: General Arithmetic. (line 6) * integers, arbitrary precision: Arbitrary Precision Integers. (line 6) -* integers, unsigned: General Arithmetic. (line 15) -* interacting with other programs: I/O Functions. (line 72) +* integers, unsigned: Computer Arithmetic. (line 41) +* interacting with other programs: I/O Functions. (line 75) * internationalization <1>: I18N and L10N. (line 6) * internationalization: I18N Functions. (line 6) * internationalization, localization <1>: Internationalization. (line 13) -* internationalization, localization: User-modified. (line 162) +* internationalization, localization: User-modified. (line 152) * internationalization, localization, character classes: Bracket Expressions. - (line 90) + (line 100) * internationalization, localization, gawk and: Internationalization. (line 13) * internationalization, localization, locale categories: Explaining gettext. - (line 80) + (line 81) * internationalization, localization, marked strings: Programmer i18n. (line 14) * internationalization, localization, portability and: I18N Portability. (line 6) * internationalizing a program: Explaining gettext. (line 6) -* interpreted programs <1>: Glossary. (line 357) +* interpreted programs <1>: Glossary. (line 356) * interpreted programs: Basic High Level. (line 15) * interval expressions, regexp operator: Regexp Operators. (line 116) * inventory-shipped file: Sample Data Files. (line 32) -* invoke shell command: I/O Functions. (line 72) +* invoke shell command: I/O Functions. (line 75) * isarray: Type Functions. (line 11) -* ISO: Glossary. (line 368) +* ISO: Glossary. (line 367) * ISO 8859-1: Glossary. (line 133) * ISO Latin-1: Glossary. (line 133) * Jacobs, Andrew: Passwd Functions. (line 90) * Jaegermann, Michal <1>: Contributors. (line 45) * Jaegermann, Michal: Acknowledgments. (line 60) -* Java implementation of awk: Other Versions. (line 112) -* Java programming language: Glossary. (line 380) -* jawk: Other Versions. (line 112) +* Java implementation of awk: Other Versions. (line 113) +* Java programming language: Glossary. (line 379) +* jawk: Other Versions. (line 113) * Jedi knights: Undocumented. (line 6) +* Johansen, Chris: Signature Program. (line 25) * join() user-defined function: Join Function. (line 18) * Kahrs, Ju"rgen <1>: Contributors. (line 70) * Kahrs, Ju"rgen: Acknowledgments. (line 60) * Kasal, Stepan: Acknowledgments. (line 60) * Kenobi, Obi-Wan: Undocumented. (line 6) * Kernighan, Brian <1>: Glossary. (line 143) -* Kernighan, Brian <2>: Basic Data Typing. (line 55) +* Kernighan, Brian <2>: Basic Data Typing. (line 54) * Kernighan, Brian <3>: Other Versions. (line 13) * Kernighan, Brian <4>: Contributors. (line 11) * Kernighan, Brian <5>: BTL. (line 6) * Kernighan, Brian <6>: Library Functions. (line 12) * Kernighan, Brian <7>: Concatenation. (line 6) * Kernighan, Brian <8>: Getline/Pipe. (line 6) -* Kernighan, Brian <9>: Acknowledgments. (line 72) -* Kernighan, Brian <10>: Conventions. (line 34) +* Kernighan, Brian <9>: Acknowledgments. (line 76) +* Kernighan, Brian <10>: Conventions. (line 38) * Kernighan, Brian: History. (line 17) * kill command, dynamic profiling: Profiling. (line 188) * Knights, jedi: Undocumented. (line 6) -* Knuth, Donald: Arbitrary Precision Arithmetic. - (line 6) * Kwok, Conrad: Contributors. (line 34) * l debugger command (alias for list): Miscellaneous Debugger Commands. (line 72) * labels.awk program: Labels Program. (line 51) +* Langston, Peter: Advanced Features. (line 6) * languages, data-driven: Basic High Level. (line 85) -* Laurie, Dirk: Changing Precision. (line 6) -* LC_ALL locale category: Explaining gettext. (line 120) -* LC_COLLATE locale category: Explaining gettext. (line 93) -* LC_CTYPE locale category: Explaining gettext. (line 97) -* LC_MESSAGES locale category: Explaining gettext. (line 87) +* LC_ALL locale category: Explaining gettext. (line 117) +* LC_COLLATE locale category: Explaining gettext. (line 94) +* LC_CTYPE locale category: Explaining gettext. (line 98) +* LC_MESSAGES locale category: Explaining gettext. (line 88) * LC_MESSAGES locale category, bindtextdomain() function (gawk): Programmer i18n. - (line 88) -* LC_MONETARY locale category: Explaining gettext. (line 103) -* LC_NUMERIC locale category: Explaining gettext. (line 107) -* LC_RESPONSE locale category: Explaining gettext. (line 111) -* LC_TIME locale category: Explaining gettext. (line 115) + (line 99) +* LC_MONETARY locale category: Explaining gettext. (line 104) +* LC_NUMERIC locale category: Explaining gettext. (line 108) +* LC_TIME locale category: Explaining gettext. (line 112) * left angle bracket (<), < operator <1>: Precedence. (line 65) * left angle bracket (<), < operator: Comparison Operators. (line 11) @@ -31895,12 +32892,12 @@ Index * left shift: Bitwise Functions. (line 46) * left shift, bitwise: Bitwise Functions. (line 32) * leftmost longest match: Multiple Line. (line 26) -* length: String Functions. (line 164) -* length of input record: String Functions. (line 171) -* length of string: String Functions. (line 164) -* Lesser General Public License (LGPL): Glossary. (line 397) -* LGPL (Lesser General Public License): Glossary. (line 397) -* libmawk: Other Versions. (line 120) +* length: String Functions. (line 167) +* length of input record: String Functions. (line 174) +* length of string: String Functions. (line 167) +* Lesser General Public License (LGPL): Glossary. (line 396) +* LGPL (Lesser General Public License): Glossary. (line 396) +* libmawk: Other Versions. (line 121) * libraries of awk functions: Library Functions. (line 6) * libraries of awk functions, assertions: Assert Function. (line 6) * libraries of awk functions, associative arrays and: Library Names. @@ -31933,35 +32930,37 @@ Index * lines, duplicate, removing: History Sorting. (line 6) * lines, matching ranges of: Ranges. (line 6) * lines, skipping between markers: Ranges. (line 43) -* lint checking: User-modified. (line 98) +* lint checking: User-modified. (line 88) * lint checking, array elements: Delete. (line 34) * lint checking, array subscripts: Uninitialized Subscripts. (line 43) * lint checking, empty programs: Command Line. (line 16) -* lint checking, issuing warnings: Options. (line 182) +* lint checking, issuing warnings: Options. (line 185) * lint checking, POSIXLY_CORRECT environment variable: Options. - (line 332) + (line 336) * lint checking, undefined functions: Pass By Value/Reference. (line 88) -* LINT variable: User-modified. (line 98) -* Linux <1>: Glossary. (line 616) +* LINT variable: User-modified. (line 88) +* Linux <1>: Glossary. (line 611) * Linux <2>: I18N Example. (line 55) * Linux: Manual History. (line 28) * list all global variables, in debugger: Debugger Info. (line 48) * list debugger command: Miscellaneous Debugger Commands. (line 72) * list function definitions, in debugger: Debugger Info. (line 30) -* loading, library: Options. (line 173) +* loading extensions, @load directive: Loading Shared Libraries. + (line 8) +* loading, extensions: Options. (line 173) * local variables, in a function: Variable Scope. (line 6) -* locale categories: Explaining gettext. (line 80) -* locale decimal point character: Options. (line 263) +* locale categories: Explaining gettext. (line 81) +* locale decimal point character: Options. (line 268) * locale, definition of: Locales. (line 6) * localization: I18N and L10N. (line 6) * localization, See internationalization, localization: I18N and L10N. (line 6) -* log: Numeric Functions. (line 30) +* log: Numeric Functions. (line 45) * log files, timestamps in: Time Functions. (line 6) -* logarithm: Numeric Functions. (line 30) +* logarithm: Numeric Functions. (line 45) * logical false/true: Truth Values. (line 6) * logical operators, See Boolean expressions: Boolean Ops. (line 6) * login information: Passwd Functions. (line 16) @@ -31982,44 +32981,45 @@ Index * mail-list file: Sample Data Files. (line 6) * mailing labels, printing: Labels Program. (line 6) * mailing list, GNITS: Acknowledgments. (line 52) -* Malmberg, John <1>: Bugs. (line 70) +* Malmberg, John <1>: Bugs. (line 71) * Malmberg, John: Acknowledgments. (line 60) * mark parity: Ordinal Functions. (line 45) * marked string extraction (internationalization): String Extraction. (line 6) * marked strings, extracting: String Extraction. (line 6) * Marx, Groucho: Increment Ops. (line 60) -* match: String Functions. (line 204) -* match regexp in string: String Functions. (line 204) +* match: String Functions. (line 207) +* match regexp in string: String Functions. (line 207) * match() function, RSTART/RLENGTH variables: String Functions. - (line 221) + (line 224) * matching, expressions, See comparison expressions: Typing and Comparison. (line 9) * matching, leftmost longest: Multiple Line. (line 26) -* matching, null strings: Gory Details. (line 164) +* matching, null strings: Gory Details. (line 143) * mawk utility <1>: Other Versions. (line 44) * mawk utility <2>: Nextfile Statement. (line 47) * mawk utility <3>: Concatenation. (line 36) * mawk utility <4>: Getline/Pipe. (line 62) -* mawk utility: Escape Sequences. (line 124) -* maximum precision supported by MPFR library: Auto-set. (line 227) +* mawk utility: Escape Sequences. (line 132) +* maximum precision supported by MPFR library: Auto-set. (line 228) +* McIlroy, Doug: Glossary. (line 149) * McPhee, Patrick: Contributors. (line 100) -* message object files: Explaining gettext. (line 41) +* message object files: Explaining gettext. (line 42) * message object files, converting from portable object files: I18N Example. - (line 62) + (line 63) * message object files, specifying directory of <1>: Programmer i18n. (line 47) * message object files, specifying directory of: Explaining gettext. - (line 53) + (line 54) * messages from extensions: Printing Messages. (line 6) * metacharacters in regular expressions: Regexp Operators. (line 6) -* metacharacters, escape sequences for: Escape Sequences. (line 130) -* minimum precision supported by MPFR library: Auto-set. (line 230) +* metacharacters, escape sequences for: Escape Sequences. (line 138) +* minimum precision supported by MPFR library: Auto-set. (line 231) * mktime: Time Functions. (line 25) * modifiers, in format specifiers: Format Modifiers. (line 6) -* monetary information, localization: Explaining gettext. (line 103) -* MPFR: Gawk and MPFR. (line 6) -* msgfmt utility: I18N Example. (line 62) +* monetary information, localization: Explaining gettext. (line 104) +* Moore, Duncan: Getline Notes. (line 40) +* msgfmt utility: I18N Example. (line 63) * multiple precision: Arbitrary Precision Arithmetic. (line 6) * multiple-line records: Multiple Line. (line 6) @@ -32028,46 +33028,44 @@ Index * names, arrays/variables <1>: Library Names. (line 6) * names, arrays/variables: Arrays. (line 18) * names, functions <1>: Library Names. (line 6) -* names, functions: Definition Syntax. (line 20) +* names, functions: Definition Syntax. (line 23) * namespace issues <1>: Library Names. (line 6) * namespace issues: Arrays. (line 18) -* namespace issues, functions: Definition Syntax. (line 20) -* nawk utility: Names. (line 17) -* negative zero: Unexpected Results. (line 34) -* NetBSD: Glossary. (line 616) +* namespace issues, functions: Definition Syntax. (line 23) +* NetBSD: Glossary. (line 611) * networks, programming: TCP/IP Networking. (line 6) * networks, support for: Special Network. (line 6) * newlines <1>: Boolean Ops. (line 67) -* newlines <2>: Options. (line 253) +* newlines <2>: Options. (line 258) * newlines: Statements/Lines. (line 6) * newlines, as field separators: Default Field Splitting. (line 6) -* newlines, as record separators: Records. (line 20) -* newlines, in dynamic regexps: Computed Regexps. (line 58) -* newlines, in regexp constants: Computed Regexps. (line 68) +* newlines, as record separators: awk split records. (line 12) +* newlines, in dynamic regexps: Computed Regexps. (line 59) +* newlines, in regexp constants: Computed Regexps. (line 69) * newlines, printing: Print Examples. (line 12) * newlines, separating statements in actions <1>: Statements. (line 10) * newlines, separating statements in actions: Action Overview. (line 19) * next debugger command: Debugger Execution Control. (line 43) -* next file statement: Feature History. (line 168) +* next file statement: Feature History. (line 169) * next statement <1>: Next Statement. (line 6) -* next statement: Boolean Ops. (line 85) -* next statement, BEGIN/END patterns and: I/O And BEGIN/END. (line 37) +* next statement: Boolean Ops. (line 93) +* next statement, BEGIN/END patterns and: I/O And BEGIN/END. (line 36) * next statement, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE. (line 49) -* next statement, user-defined functions and: Next Statement. (line 45) +* next statement, user-defined functions and: Next Statement. (line 44) * nextfile statement: Nextfile Statement. (line 6) * nextfile statement, BEGIN/END patterns and: I/O And BEGIN/END. - (line 37) + (line 36) * nextfile statement, BEGINFILE/ENDFILE patterns and: BEGINFILE/ENDFILE. (line 26) * nextfile statement, user-defined functions and: Nextfile Statement. (line 47) * nexti debugger command: Debugger Execution Control. (line 49) -* NF variable <1>: Auto-set. (line 117) +* NF variable <1>: Auto-set. (line 112) * NF variable: Fields. (line 33) * NF variable, decrementing: Changing Fields. (line 107) * ni debugger command (alias for nexti): Debugger Execution Control. @@ -32076,22 +33074,23 @@ Index * non-existent array elements: Reference to Elements. (line 23) * not Boolean-logic operator: Boolean Ops. (line 6) -* NR variable <1>: Auto-set. (line 137) +* NR variable <1>: Auto-set. (line 132) * NR variable: Records. (line 6) -* NR variable, changing: Auto-set. (line 323) +* NR variable, changing: Auto-set. (line 316) * null strings <1>: Basic Data Typing. (line 26) * null strings <2>: Truth Values. (line 6) * null strings <3>: Regexp Field Splitting. (line 43) -* null strings: Records. (line 122) -* null strings in gawk arguments, quoting and: Quoting. (line 62) +* null strings: awk split records. (line 114) +* null strings in gawk arguments, quoting and: Quoting. (line 79) * null strings, and deleting array elements: Delete. (line 27) * null strings, as array subscripts: Uninitialized Subscripts. (line 43) -* null strings, converting numbers to strings: Conversion. (line 21) -* null strings, matching: Gory Details. (line 164) +* null strings, converting numbers to strings: Strings And Numbers. + (line 21) +* null strings, matching: Gory Details. (line 143) * number as string of bits: Bitwise Functions. (line 109) -* number of array elements: String Functions. (line 194) +* number of array elements: String Functions. (line 197) * number sign (#), #! (executable scripts): Executable Scripts. (line 6) * number sign (#), commenting: Comments. (line 6) @@ -32101,9 +33100,8 @@ Index * numbers, Cliff random: Cliff Random Function. (line 6) * numbers, converting <1>: Bitwise Functions. (line 109) -* numbers, converting: Conversion. (line 6) -* numbers, converting, to strings: User-modified. (line 28) -* numbers, floating-point: General Arithmetic. (line 6) +* numbers, converting: Strings And Numbers. (line 6) +* numbers, converting, to strings: User-modified. (line 30) * numbers, hexadecimal: Nondecimal-numbers. (line 6) * numbers, octal: Nondecimal-numbers. (line 6) * numbers, rounding: Round Function. (line 6) @@ -32112,18 +33110,17 @@ Index * numeric, output format: OFMT. (line 6) * numeric, strings: Variable Typing. (line 6) * o debugger command (alias for option): Debugger Info. (line 57) -* oawk utility: Names. (line 17) * obsolete features: Obsolete. (line 6) * octal numbers: Nondecimal-numbers. (line 6) -* octal values, enabling interpretation of: Options. (line 207) -* OFMT variable <1>: User-modified. (line 115) -* OFMT variable <2>: Conversion. (line 55) +* octal values, enabling interpretation of: Options. (line 211) +* OFMT variable <1>: User-modified. (line 105) +* OFMT variable <2>: Strings And Numbers. (line 57) * OFMT variable: OFMT. (line 15) * OFMT variable, POSIX awk and: OFMT. (line 27) -* OFS variable <1>: User-modified. (line 124) +* OFS variable <1>: User-modified. (line 114) * OFS variable <2>: Output Separators. (line 6) * OFS variable: Changing Fields. (line 64) -* OpenBSD: Glossary. (line 616) +* OpenBSD: Glossary. (line 611) * OpenSolaris: Other Versions. (line 96) * operating systems, BSD-based: Manual History. (line 28) * operating systems, PC, gawk on: PC Using. (line 6) @@ -32173,14 +33170,14 @@ Index (line 12) * ord() user-defined function: Ordinal Functions. (line 16) * order of evaluation, concatenation: Concatenation. (line 41) -* ORS variable <1>: User-modified. (line 129) +* ORS variable <1>: User-modified. (line 119) * ORS variable: Output Separators. (line 20) * output field separator, See OFS variable: Changing Fields. (line 64) * output record separator, See ORS variable: Output Separators. (line 20) * output redirection: Redirection. (line 6) * output wrapper: Output Wrappers. (line 6) -* output, buffering: I/O Functions. (line 29) +* output, buffering: I/O Functions. (line 32) * output, duplicating into files: Tee Program. (line 6) * output, files, closing: Close Files And Pipes. (line 6) @@ -32192,12 +33189,12 @@ Index * output, standard: Special FD. (line 6) * p debugger command (alias for print): Viewing And Changing Data. (line 36) -* P1003.1 POSIX standard: Glossary. (line 454) -* parent process ID of gawk process: Auto-set. (line 195) +* Papadopoulos, Panos: Contributors. (line 128) +* parent process ID of gawk process: Auto-set. (line 196) * parentheses (), in a profile: Profiling. (line 146) -* parentheses (), regexp operator: Regexp Operators. (line 79) +* parentheses (), regexp operator: Regexp Operators. (line 81) * password file: Passwd Functions. (line 16) -* patsplit: String Functions. (line 291) +* patsplit: String Functions. (line 294) * patterns: Patterns and Actions. (line 6) * patterns, comparison expressions as: Expression Patterns. (line 14) @@ -32210,13 +33207,13 @@ Index * patterns, types of: Pattern Overview. (line 15) * pawk (profiling version of Brian Kernighan's awk): Other Versions. (line 78) -* pawk, awk-like facilities for Python: Other Versions. (line 124) +* pawk, awk-like facilities for Python: Other Versions. (line 125) * PC operating systems, gawk on: PC Using. (line 6) * PC operating systems, gawk on, installing: PC Installation. (line 6) * percent sign (%), % operator: Precedence. (line 55) * percent sign (%), %= operator <1>: Precedence. (line 95) -* percent sign (%), %= operator: Assignment Ops. (line 129) -* period (.), regexp operator: Regexp Operators. (line 43) +* percent sign (%), %= operator: Assignment Ops. (line 130) +* period (.), regexp operator: Regexp Operators. (line 44) * Perl: Future Extensions. (line 6) * Peters, Arno: Contributors. (line 85) * Peterson, Hal: Contributors. (line 39) @@ -32224,7 +33221,7 @@ Index (line 6) * pipe, input: Getline/Pipe. (line 9) * pipe, output: Redirection. (line 57) -* Pitts, Dave <1>: Bugs. (line 70) +* Pitts, Dave <1>: Bugs. (line 71) * Pitts, Dave: Acknowledgments. (line 60) * Plauger, P.J.: Library Functions. (line 12) * plug-in: Extension Intro. (line 6) @@ -32233,89 +33230,88 @@ Index * plus sign (+), ++ operator: Increment Ops. (line 11) * plus sign (+), += operator <1>: Precedence. (line 95) * plus sign (+), += operator: Assignment Ops. (line 82) -* plus sign (+), regexp operator: Regexp Operators. (line 102) +* plus sign (+), regexp operator: Regexp Operators. (line 105) * pointers to functions: Indirect Calls. (line 6) -* portability: Escape Sequences. (line 94) +* portability: Escape Sequences. (line 102) * portability, #! (executable scripts): Executable Scripts. (line 33) * portability, ** operator and: Arithmetic Ops. (line 81) -* portability, **= operator and: Assignment Ops. (line 142) -* portability, ARGV variable: Executable Scripts. (line 42) +* portability, **= operator and: Assignment Ops. (line 143) +* portability, ARGV variable: Executable Scripts. (line 59) * portability, backslash continuation and: Statements/Lines. (line 30) * portability, backslash in escape sequences: Escape Sequences. - (line 112) + (line 120) * portability, close() function and: Close Files And Pipes. (line 81) -* portability, data files as single record: Records. (line 194) +* portability, data files as single record: gawk split records. + (line 65) * portability, deleting array elements: Delete. (line 56) * portability, example programs: Library Functions. (line 42) -* portability, functions, defining: Definition Syntax. (line 99) +* portability, functions, defining: Definition Syntax. (line 109) * portability, gawk: New Ports. (line 6) -* portability, gettext library and: Explaining gettext. (line 10) +* portability, gettext library and: Explaining gettext. (line 11) * portability, internationalization and: I18N Portability. (line 6) -* portability, length() function: String Functions. (line 173) -* portability, new awk vs. old awk: Conversion. (line 55) +* portability, length() function: String Functions. (line 176) +* portability, new awk vs. old awk: Strings And Numbers. (line 57) * portability, next statement in user-defined functions: Pass By Value/Reference. (line 91) * portability, NF variable, decrementing: Changing Fields. (line 115) * portability, operators: Increment Ops. (line 60) * portability, operators, not in POSIX awk: Precedence. (line 98) -* portability, POSIXLY_CORRECT environment variable: Options. (line 353) +* portability, POSIXLY_CORRECT environment variable: Options. (line 356) * portability, substr() function: String Functions. (line 510) * portable object files <1>: Translator i18n. (line 6) -* portable object files: Explaining gettext. (line 36) +* portable object files: Explaining gettext. (line 37) * portable object files, converting to message object files: I18N Example. - (line 62) + (line 63) * portable object files, generating: Options. (line 147) -* portable object template files: Explaining gettext. (line 30) +* portable object template files: Explaining gettext. (line 31) * porting gawk: New Ports. (line 6) * positional specifiers, printf statement <1>: Printf Ordering. (line 6) * positional specifiers, printf statement: Format Modifiers. (line 13) * positional specifiers, printf statement, mixing with regular formats: Printf Ordering. (line 57) -* positive zero: Unexpected Results. (line 34) -* POSIX awk <1>: Assignment Ops. (line 136) +* POSIX awk <1>: Assignment Ops. (line 137) * POSIX awk: This Manual. (line 14) * POSIX awk, ** operator and: Precedence. (line 98) -* POSIX awk, **= operator and: Assignment Ops. (line 142) +* POSIX awk, **= operator and: Assignment Ops. (line 143) * POSIX awk, < operator and: Getline/File. (line 26) * POSIX awk, arithmetic operators and: Arithmetic Ops. (line 30) * POSIX awk, backslashes in string constants: Escape Sequences. - (line 112) + (line 120) * POSIX awk, BEGIN/END patterns: I/O And BEGIN/END. (line 16) -* POSIX awk, bracket expressions and: Bracket Expressions. (line 24) +* POSIX awk, bracket expressions and: Bracket Expressions. (line 26) * POSIX awk, bracket expressions and, character classes: Bracket Expressions. - (line 30) + (line 32) * POSIX awk, break statement and: Break Statement. (line 51) * POSIX awk, changes in awk versions: POSIX. (line 6) -* POSIX awk, continue statement and: Continue Statement. (line 43) -* POSIX awk, CONVFMT variable and: User-modified. (line 28) -* POSIX awk, date utility and: Time Functions. (line 263) +* POSIX awk, continue statement and: Continue Statement. (line 44) +* POSIX awk, CONVFMT variable and: User-modified. (line 30) +* POSIX awk, date utility and: Time Functions. (line 254) * POSIX awk, field separators and <1>: Field Splitting Summary. (line 40) * POSIX awk, field separators and: Fields. (line 6) -* POSIX awk, FS variable and: User-modified. (line 66) -* POSIX awk, function keyword in: Definition Syntax. (line 83) -* POSIX awk, functions and, gsub()/sub(): Gory Details. (line 54) -* POSIX awk, functions and, length(): String Functions. (line 173) +* POSIX awk, FS variable and: User-modified. (line 60) +* POSIX awk, function keyword in: Definition Syntax. (line 93) +* POSIX awk, functions and, gsub()/sub(): Gory Details. (line 90) +* POSIX awk, functions and, length(): String Functions. (line 176) * POSIX awk, GNU long options and: Options. (line 15) * POSIX awk, interval expressions in: Regexp Operators. (line 135) -* POSIX awk, next/nextfile statements and: Next Statement. (line 45) +* POSIX awk, next/nextfile statements and: Next Statement. (line 44) * POSIX awk, numeric strings and: Variable Typing. (line 6) -* POSIX awk, OFMT variable and <1>: Conversion. (line 55) +* POSIX awk, OFMT variable and <1>: Strings And Numbers. (line 57) * POSIX awk, OFMT variable and: OFMT. (line 27) -* POSIX awk, period (.), using: Regexp Operators. (line 50) +* POSIX awk, period (.), using: Regexp Operators. (line 51) * POSIX awk, printf format strings and: Format Modifiers. (line 159) * POSIX awk, regular expressions and: Regexp Operators. (line 161) * POSIX awk, timestamps and: Time Functions. (line 6) * POSIX awk, | I/O operator and: Getline/Pipe. (line 55) -* POSIX mode: Options. (line 247) -* POSIX, awk and: Preface. (line 23) +* POSIX mode: Options. (line 252) +* POSIX, awk and: Preface. (line 21) * POSIX, gawk extensions not included in: POSIX/GNU. (line 6) * POSIX, programs, implementing in awk: Clones. (line 6) -* POSIXLY_CORRECT environment variable: Options. (line 332) -* PREC variable <1>: Setting Precision. (line 6) -* PREC variable: User-modified. (line 134) +* POSIXLY_CORRECT environment variable: Options. (line 336) +* PREC variable: User-modified. (line 124) * precedence <1>: Precedence. (line 6) * precedence: Increment Ops. (line 60) * precedence, regexp operators: Regexp Operators. (line 156) @@ -32326,7 +33322,7 @@ Index * print statement, commas, omitting: Print Examples. (line 31) * print statement, I/O operators in: Precedence. (line 71) * print statement, line continuations and: Print Examples. (line 76) -* print statement, OFMT variable and: User-modified. (line 124) +* print statement, OFMT variable and: User-modified. (line 114) * print statement, See Also redirection, of output: Redirection. (line 17) * print statement, sprintf() function and: Round Function. (line 6) @@ -32357,78 +33353,77 @@ Index * printing, unduplicated lines of text: Uniq Program. (line 6) * printing, user information: Id Program. (line 6) * private variables: Library Names. (line 11) -* process group idIDof gawk process: Auto-set. (line 189) -* process ID of gawk process: Auto-set. (line 192) -* processes, two-way communications with: Two-way I/O. (line 23) +* process group idIDof gawk process: Auto-set. (line 190) +* process ID of gawk process: Auto-set. (line 193) +* processes, two-way communications with: Two-way I/O. (line 6) * processing data: Basic High Level. (line 6) * PROCINFO array <1>: Passwd Functions. (line 6) * PROCINFO array <2>: Time Functions. (line 47) -* PROCINFO array: Auto-set. (line 142) -* PROCINFO array, and communications via ptys: Two-way I/O. (line 116) +* PROCINFO array: Auto-set. (line 137) +* PROCINFO array, and communications via ptys: Two-way I/O. (line 99) * PROCINFO array, and group membership: Group Functions. (line 6) * PROCINFO array, and user and group ID numbers: Id Program. (line 15) * PROCINFO array, testing the field splitting: Passwd Functions. (line 161) -* PROCINFO array, uses: Auto-set. (line 248) +* PROCINFO array, uses: Auto-set. (line 249) * PROCINFO, values of sorted_in: Controlling Scanning. - (line 24) + (line 26) * profiling awk programs: Profiling. (line 6) * profiling awk programs, dynamically: Profiling. (line 179) -* program identifiers: Auto-set. (line 160) +* program identifiers: Auto-set. (line 155) * program, definition of: Getting Started. (line 21) -* programmers, attractiveness of: Two-way I/O. (line 6) * programming conventions, --non-decimal-data option: Nondecimal Data. (line 36) -* programming conventions, ARGC/ARGV variables: Auto-set. (line 31) +* programming conventions, ARGC/ARGV variables: Auto-set. (line 35) * programming conventions, exit statement: Exit Statement. (line 38) * programming conventions, function parameters: Return Statement. (line 45) * programming conventions, functions, calling: Calling Built-in. (line 10) * programming conventions, functions, writing: Definition Syntax. - (line 55) + (line 65) * programming conventions, gawk extensions: Internal File Ops. (line 45) * programming conventions, private variable names: Library Names. (line 23) * programming language, recipe for: History. (line 6) -* programming languages, Ada: Glossary. (line 20) +* programming languages, Ada: Glossary. (line 19) * programming languages, data-driven vs. procedural: Getting Started. (line 12) -* programming languages, Java: Glossary. (line 380) +* programming languages, Java: Glossary. (line 379) * programming, basic steps: Basic High Level. (line 20) * programming, concepts: Basic Concepts. (line 6) * pwcat program: Passwd Functions. (line 23) * q debugger command (alias for quit): Miscellaneous Debugger Commands. (line 99) -* QSE Awk: Other Versions. (line 130) +* QSE Awk: Other Versions. (line 131) * Quanstrom, Erik: Alarm Program. (line 8) * question mark (?), ?: operator: Precedence. (line 92) * question mark (?), regexp operator <1>: GNU Regexp Operators. (line 59) * question mark (?), regexp operator: Regexp Operators. (line 111) -* QuikTrim Awk: Other Versions. (line 134) +* QuikTrim Awk: Other Versions. (line 135) * quit debugger command: Miscellaneous Debugger Commands. (line 99) * QUIT signal (MS-Windows): Profiling. (line 214) * quoting in gawk command lines: Long. (line 26) -* quoting in gawk command lines, tricks for: Quoting. (line 71) +* quoting in gawk command lines, tricks for: Quoting. (line 88) * quoting, for small awk programs: Comments. (line 27) * r debugger command (alias for run): Debugger Execution Control. (line 62) * Rakitzis, Byron: History Sorting. (line 25) * Ramey, Chet <1>: General Data Types. (line 6) * Ramey, Chet: Acknowledgments. (line 60) -* rand: Numeric Functions. (line 34) +* rand: Numeric Functions. (line 50) * random numbers, Cliff: Cliff Random Function. (line 6) * random numbers, rand()/srand() functions: Numeric Functions. - (line 34) -* random numbers, seed of: Numeric Functions. (line 64) + (line 50) +* random numbers, seed of: Numeric Functions. (line 80) * range expressions (regexps): Bracket Expressions. (line 6) * range patterns: Ranges. (line 6) * range patterns, line continuation and: Ranges. (line 65) -* Rankin, Pat <1>: Bugs. (line 70) +* Rankin, Pat <1>: Bugs. (line 71) * Rankin, Pat <2>: Contributors. (line 37) * Rankin, Pat <3>: Assignment Ops. (line 100) * Rankin, Pat: Acknowledgments. (line 60) @@ -32443,19 +33438,20 @@ Index * readfile() user-defined function: Readfile Function. (line 30) * reading input files: Reading Files. (line 6) * recipe for a programming language: History. (line 6) -* record separators <1>: User-modified. (line 143) -* record separators: Records. (line 14) -* record separators, changing: Records. (line 93) -* record separators, regular expressions as: Records. (line 132) +* record separators <1>: User-modified. (line 133) +* record separators: awk split records. (line 6) +* record separators, changing: awk split records. (line 85) +* record separators, regular expressions as: awk split records. + (line 124) * record separators, with multiline records: Multiple Line. (line 10) * records <1>: Basic High Level. (line 73) * records: Reading Files. (line 14) * records, multiline: Multiple Line. (line 6) * records, printing: Print. (line 22) * records, splitting input into: Records. (line 6) -* records, terminating: Records. (line 132) -* records, treating files as: Records. (line 219) -* recursive functions: Definition Syntax. (line 73) +* records, terminating: awk split records. (line 124) +* records, treating files as: gawk split records. (line 92) +* recursive functions: Definition Syntax. (line 83) * redirect gawk output, in debugger: Debugger Info. (line 72) * redirection of input: Getline/File. (line 6) * redirection of output: Redirection. (line 6) @@ -32466,12 +33462,12 @@ Index (line 102) * regexp constants <2>: Regexp Constants. (line 6) * regexp constants: Regexp Usage. (line 57) -* regexp constants, /=.../, /= operator and: Assignment Ops. (line 147) +* regexp constants, /=.../, /= operator and: Assignment Ops. (line 148) * regexp constants, as patterns: Expression Patterns. (line 34) * regexp constants, in gawk: Using Constant Regexps. (line 28) -* regexp constants, slashes vs. quotes: Computed Regexps. (line 28) -* regexp constants, vs. string constants: Computed Regexps. (line 38) +* regexp constants, slashes vs. quotes: Computed Regexps. (line 29) +* regexp constants, vs. string constants: Computed Regexps. (line 39) * register extension: Registration Functions. (line 6) * regular expressions: Regexp. (line 6) @@ -32481,18 +33477,19 @@ Index (line 6) * regular expressions, as patterns <1>: Regexp Patterns. (line 6) * regular expressions, as patterns: Regexp Usage. (line 6) -* regular expressions, as record separators: Records. (line 132) -* regular expressions, case sensitivity <1>: User-modified. (line 82) +* regular expressions, as record separators: awk split records. + (line 124) +* regular expressions, case sensitivity <1>: User-modified. (line 76) * regular expressions, case sensitivity: Case-sensitivity. (line 6) * regular expressions, computed: Computed Regexps. (line 6) * regular expressions, constants, See regexp constants: Regexp Usage. (line 57) * regular expressions, dynamic: Computed Regexps. (line 6) * regular expressions, dynamic, with embedded newlines: Computed Regexps. - (line 58) + (line 59) * regular expressions, gawk, command-line options: GNU Regexp Operators. (line 70) -* regular expressions, interval expressions and: Options. (line 272) +* regular expressions, interval expressions and: Options. (line 277) * regular expressions, leftmost longest match: Leftmost Longest. (line 6) * regular expressions, operators <1>: Regexp Operators. (line 6) @@ -32513,8 +33510,8 @@ Index (line 54) * return statement, user-defined functions: Return Statement. (line 6) * return value, close() function: Close Files And Pipes. - (line 130) -* rev() user-defined function: Function Example. (line 53) + (line 131) +* rev() user-defined function: Function Example. (line 54) * revoutput extension: Extension Sample Revout. (line 11) * revtwoway extension: Extension Sample Rev2way. @@ -32531,41 +33528,38 @@ Index * right angle bracket (>), >> operator (I/O): Redirection. (line 50) * right shift: Bitwise Functions. (line 52) * right shift, bitwise: Bitwise Functions. (line 32) -* Ritchie, Dennis: Basic Data Typing. (line 55) -* RLENGTH variable: Auto-set. (line 262) -* RLENGTH variable, match() function and: String Functions. (line 221) +* Ritchie, Dennis: Basic Data Typing. (line 54) +* RLENGTH variable: Auto-set. (line 259) +* RLENGTH variable, match() function and: String Functions. (line 224) * Robbins, Arnold <1>: Future Extensions. (line 6) * Robbins, Arnold <2>: Bugs. (line 32) -* Robbins, Arnold <3>: Contributors. (line 139) +* Robbins, Arnold <3>: Contributors. (line 141) * Robbins, Arnold <4>: General Data Types. (line 6) * Robbins, Arnold <5>: Alarm Program. (line 6) * Robbins, Arnold <6>: Passwd Functions. (line 90) * Robbins, Arnold <7>: Getline/Pipe. (line 39) * Robbins, Arnold: Command Line Field Separator. - (line 73) + (line 74) * Robbins, Bill: Getline/Pipe. (line 39) -* Robbins, Harry: Acknowledgments. (line 78) -* Robbins, Jean: Acknowledgments. (line 78) +* Robbins, Harry: Acknowledgments. (line 92) +* Robbins, Jean: Acknowledgments. (line 92) * Robbins, Miriam <1>: Passwd Functions. (line 90) * Robbins, Miriam <2>: Getline/Pipe. (line 39) -* Robbins, Miriam: Acknowledgments. (line 78) +* Robbins, Miriam: Acknowledgments. (line 92) * Rommel, Kai Uwe: Contributors. (line 42) -* round to nearest integer: Numeric Functions. (line 23) +* round to nearest integer: Numeric Functions. (line 38) * round() user-defined function: Round Function. (line 16) -* rounding mode, floating-point: Rounding Mode. (line 6) * rounding numbers: Round Function. (line 6) -* ROUNDMODE variable <1>: Setting Rounding Mode. - (line 6) -* ROUNDMODE variable: User-modified. (line 138) -* RS variable <1>: User-modified. (line 143) -* RS variable: Records. (line 20) +* ROUNDMODE variable: User-modified. (line 128) +* RS variable <1>: User-modified. (line 133) +* RS variable: awk split records. (line 12) * RS variable, multiline records and: Multiple Line. (line 17) * rshift: Bitwise Functions. (line 52) -* RSTART variable: Auto-set. (line 268) -* RSTART variable, match() function and: String Functions. (line 221) -* RT variable <1>: Auto-set. (line 275) +* RSTART variable: Auto-set. (line 265) +* RSTART variable, match() function and: String Functions. (line 224) +* RT variable <1>: Auto-set. (line 272) * RT variable <2>: Multiple Line. (line 129) -* RT variable: Records. (line 132) +* RT variable: awk split records. (line 124) * Rubin, Paul <1>: Contributors. (line 15) * Rubin, Paul: History. (line 30) * rule, definition of: Getting Started. (line 21) @@ -32576,33 +33570,34 @@ Index (line 68) * sample debugging session: Sample Debugging Session. (line 6) -* sandbox mode: Options. (line 279) +* sandbox mode: Options. (line 284) * save debugger options: Debugger Info. (line 84) * scalar or array: Type Functions. (line 11) * scalar values: Basic Data Typing. (line 13) * scanning arrays: Scanning an Array. (line 6) * scanning multidimensional arrays: Multiscanning. (line 11) -* Schorr, Andrew <1>: Contributors. (line 131) +* Schorr, Andrew <1>: Contributors. (line 133) +* Schorr, Andrew <2>: Auto-set. (line 299) * Schorr, Andrew: Acknowledgments. (line 60) * Schreiber, Bert: Acknowledgments. (line 38) * Schreiber, Rita: Acknowledgments. (line 38) -* search and replace in strings: String Functions. (line 82) -* search in string: String Functions. (line 151) +* search and replace in strings: String Functions. (line 89) +* search in string: String Functions. (line 155) * search paths <1>: VMS Running. (line 58) * search paths <2>: PC Using. (line 10) -* search paths: Igawk Program. (line 368) -* search paths, for shared libraries: AWKLIBPATH Variable. (line 6) +* search paths: Programs Exercises. (line 70) +* search paths, for loadable extensions: AWKLIBPATH Variable. (line 6) * search paths, for source files <1>: VMS Running. (line 58) * search paths, for source files <2>: PC Using. (line 10) -* search paths, for source files <3>: Igawk Program. (line 368) +* search paths, for source files <3>: Programs Exercises. (line 70) * search paths, for source files: AWKPATH Variable. (line 6) * searching, files for regular expressions: Egrep Program. (line 6) * searching, for words: Dupword Program. (line 6) -* sed utility <1>: Glossary. (line 12) +* sed utility <1>: Glossary. (line 11) * sed utility <2>: Simple Sed. (line 6) * sed utility: Field Splitting Summary. (line 46) -* seeding random number generator: Numeric Functions. (line 64) +* seeding random number generator: Numeric Functions. (line 80) * semicolon (;), AWKPATH variable and: PC Using. (line 10) * semicolon (;), separating statements in actions <1>: Statements. (line 10) @@ -32610,26 +33605,23 @@ Index (line 19) * semicolon (;), separating statements in actions: Statements/Lines. (line 91) -* separators, field: User-modified. (line 56) -* separators, field, FIELDWIDTHS variable and: User-modified. (line 35) -* separators, field, FPAT variable and: User-modified. (line 45) +* separators, field: User-modified. (line 50) +* separators, field, FIELDWIDTHS variable and: User-modified. (line 37) +* separators, field, FPAT variable and: User-modified. (line 43) * separators, field, POSIX and: Fields. (line 6) -* separators, for records <1>: User-modified. (line 143) -* separators, for records: Records. (line 14) -* separators, for records, regular expressions as: Records. (line 132) +* separators, for records <1>: User-modified. (line 133) +* separators, for records: awk split records. (line 6) +* separators, for records, regular expressions as: awk split records. + (line 124) * separators, for statements in actions: Action Overview. (line 19) -* separators, subscript: User-modified. (line 156) +* separators, subscript: User-modified. (line 146) * set breakpoint: Breakpoint Control. (line 11) * set debugger command: Viewing And Changing Data. (line 59) * set directory of message catalogs: I18N Functions. (line 12) * set watchpoint: Viewing And Changing Data. (line 67) -* setting rounding mode: Setting Rounding Mode. - (line 6) -* setting working precision: Setting Precision. (line 6) -* shadowing of variable values: Definition Syntax. (line 61) -* shell quoting, double quote: Read Terminal. (line 25) +* shadowing of variable values: Definition Syntax. (line 71) * shell quoting, rules for: Quoting. (line 6) * shells, piping commands into: Redirection. (line 142) * shells, quoting: Using Shell Variables. @@ -32653,7 +33645,7 @@ Index * side effects <1>: Increment Ops. (line 11) * side effects: Concatenation. (line 41) * side effects, array indexing: Reference to Elements. - (line 42) + (line 43) * side effects, asort() function: Array Sorting Functions. (line 24) * side effects, assignment expressions: Assignment Ops. (line 23) @@ -32661,38 +33653,40 @@ Index * side effects, conditional expressions: Conditional Exp. (line 22) * side effects, decrement/increment operators: Increment Ops. (line 11) * side effects, FILENAME variable: Getline Notes. (line 19) -* side effects, function calls: Function Calls. (line 54) +* side effects, function calls: Function Calls. (line 57) * side effects, statements: Action Overview. (line 32) * sidebar, A Constant's Base Does Not Affect Its Value: Nondecimal-numbers. (line 64) * sidebar, Backslash Before Regular Characters: Escape Sequences. - (line 110) + (line 118) * sidebar, Changing FS Does Not Affect the Fields: Field Splitting Summary. (line 38) -* sidebar, Changing NR and FNR: Auto-set. (line 321) +* sidebar, Changing NR and FNR: Auto-set. (line 314) * sidebar, Controlling Output Buffering with system(): I/O Functions. - (line 135) + (line 138) * sidebar, Escape Sequences for Metacharacters: Escape Sequences. - (line 128) + (line 136) * sidebar, FS and IGNORECASE: Field Splitting Summary. (line 64) * sidebar, Interactive Versus Noninteractive Buffering: I/O Functions. - (line 104) -* sidebar, Matching the Null String: Gory Details. (line 162) + (line 107) +* sidebar, Matching the Null String: Gory Details. (line 141) * sidebar, Operator Evaluation Order: Increment Ops. (line 58) * sidebar, Piping into sh: Redirection. (line 140) -* sidebar, Portability Issues with #!: Executable Scripts. (line 31) +* sidebar, Pre-POSIX awk Used OFMT For String Conversion: Strings And Numbers. + (line 55) * sidebar, Recipe For A Programming Language: History. (line 6) -* sidebar, RS = "\0" Is Not Portable: Records. (line 192) +* sidebar, RS = "\0" Is Not Portable: gawk split records. (line 63) * sidebar, So Why Does gawk have BEGINFILE and ENDFILE?: Filetrans Function. (line 83) * sidebar, Syntactic Ambiguities Between /= and Regular Expressions: Assignment Ops. - (line 145) + (line 146) +* sidebar, Understanding #!: Executable Scripts. (line 31) * sidebar, Understanding $0: Changing Fields. (line 134) * sidebar, Using \n in Bracket Expressions of Dynamic Regexps: Computed Regexps. - (line 56) + (line 57) * sidebar, Using close()'s Return Value: Close Files And Pipes. - (line 128) + (line 129) * SIGHUP signal, for dynamic profiling: Profiling. (line 211) * SIGINT signal (MS-Windows): Profiling. (line 214) * signals, HUP/SIGHUP, for profiling: Profiling. (line 211) @@ -32704,64 +33698,63 @@ Index * SIGUSR1 signal, for dynamic profiling: Profiling. (line 188) * silent debugger command: Debugger Execution Control. (line 10) -* sin: Numeric Functions. (line 75) -* sine: Numeric Functions. (line 75) -* single precision floating-point: General Arithmetic. (line 21) +* sin: Numeric Functions. (line 91) +* sine: Numeric Functions. (line 91) * single quote ('): One-shot. (line 15) * single quote (') in gawk command lines: Long. (line 33) -* single quote ('), in shell commands: Quoting. (line 31) +* single quote ('), in shell commands: Quoting. (line 48) * single quote ('), vs. apostrophe: Comments. (line 27) -* single quote ('), with double quotes: Quoting. (line 53) +* single quote ('), with double quotes: Quoting. (line 70) * single-character fields: Single Character Fields. (line 6) * single-step execution, in the debugger: Debugger Execution Control. (line 43) * Skywalker, Luke: Undocumented. (line 6) -* sleep utility: Alarm Program. (line 111) +* sleep utility: Alarm Program. (line 110) * sleep() extension function: Extension Sample Time. - (line 23) + (line 22) * Solaris, POSIX-compliant awk: Other Versions. (line 96) -* sort array: String Functions. (line 32) -* sort array indices: String Functions. (line 32) +* sort array: String Functions. (line 42) +* sort array indices: String Functions. (line 42) * sort function, arrays, sorting: Array Sorting Functions. (line 6) * sort utility: Word Sorting. (line 50) -* sort utility, coprocesses and: Two-way I/O. (line 83) +* sort utility, coprocesses and: Two-way I/O. (line 65) * sorting characters in different languages: Explaining gettext. - (line 93) + (line 94) * source code, awka: Other Versions. (line 64) * source code, Brian Kernighan's awk: Other Versions. (line 13) * source code, Busybox Awk: Other Versions. (line 88) * source code, gawk: Gawk Distribution. (line 6) -* source code, Illumos awk: Other Versions. (line 104) -* source code, jawk: Other Versions. (line 112) -* source code, libmawk: Other Versions. (line 120) +* source code, Illumos awk: Other Versions. (line 105) +* source code, jawk: Other Versions. (line 113) +* source code, libmawk: Other Versions. (line 121) * source code, mawk: Other Versions. (line 44) * source code, mixing: Options. (line 117) * source code, pawk: Other Versions. (line 78) -* source code, pawk (Python version): Other Versions. (line 124) -* source code, QSE Awk: Other Versions. (line 130) -* source code, QuikTrim Awk: Other Versions. (line 134) +* source code, pawk (Python version): Other Versions. (line 125) +* source code, QSE Awk: Other Versions. (line 131) +* source code, QuikTrim Awk: Other Versions. (line 135) * source code, Solaris awk: Other Versions. (line 96) -* source files, search path for: Igawk Program. (line 368) -* sparse arrays: Array Intro. (line 70) -* Spencer, Henry: Glossary. (line 12) +* source files, search path for: Programs Exercises. (line 70) +* sparse arrays: Array Intro. (line 72) +* Spencer, Henry: Glossary. (line 11) * split: String Functions. (line 313) -* split string into array: String Functions. (line 291) +* split string into array: String Functions. (line 294) * split utility: Split Program. (line 6) * split() function, array elements, deleting: Delete. (line 61) * split.awk program: Split Program. (line 30) -* sprintf <1>: String Functions. (line 378) +* sprintf <1>: String Functions. (line 381) * sprintf: OFMT. (line 15) -* sprintf() function, OFMT variable and: User-modified. (line 124) +* sprintf() function, OFMT variable and: User-modified. (line 114) * sprintf() function, print/printf statements and: Round Function. (line 6) -* sqrt: Numeric Functions. (line 78) -* square brackets ([]), regexp operator: Regexp Operators. (line 55) -* square root: Numeric Functions. (line 78) -* srand: Numeric Functions. (line 82) +* sqrt: Numeric Functions. (line 94) +* square brackets ([]), regexp operator: Regexp Operators. (line 56) +* square root: Numeric Functions. (line 94) +* srand: Numeric Functions. (line 98) * stack frame: Debugging Terms. (line 10) -* Stallman, Richard <1>: Glossary. (line 297) +* Stallman, Richard <1>: Glossary. (line 296) * Stallman, Richard <2>: Contributors. (line 23) * Stallman, Richard <3>: Acknowledgments. (line 18) * Stallman, Richard: Manual History. (line 6) @@ -32786,21 +33779,21 @@ Index (line 46) * strftime: Time Functions. (line 48) * string constants: Scalar Constants. (line 15) -* string constants, vs. regexp constants: Computed Regexps. (line 38) +* string constants, vs. regexp constants: Computed Regexps. (line 39) * string extraction (internationalization): String Extraction. (line 6) -* string length: String Functions. (line 164) +* string length: String Functions. (line 167) * string operators: Concatenation. (line 8) -* string, regular expression match: String Functions. (line 204) +* string, regular expression match: String Functions. (line 207) * string-manipulation functions: String Functions. (line 6) * string-matching operators: Regexp Usage. (line 19) * string-translation functions: I18N Functions. (line 6) * strings splitting, example: String Functions. (line 333) * strings, converting <1>: Bitwise Functions. (line 109) -* strings, converting: Conversion. (line 6) +* strings, converting: Strings And Numbers. (line 6) * strings, converting letter case: String Functions. (line 520) -* strings, converting, numbers to: User-modified. (line 28) -* strings, empty, See null strings: Records. (line 122) +* strings, converting, numbers to: User-modified. (line 30) +* strings, empty, See null strings: awk split records. (line 114) * strings, extracting: String Extraction. (line 6) * strings, for localization: Programmer i18n. (line 14) * strings, length limitations: Scalar Constants. (line 20) @@ -32808,7 +33801,7 @@ Index * strings, null: Regexp Field Splitting. (line 43) * strings, numeric: Variable Typing. (line 6) -* strtonum: String Functions. (line 385) +* strtonum: String Functions. (line 388) * strtonum() function (gawk), --non-decimal-data option and: Nondecimal Data. (line 36) * sub <1>: String Functions. (line 406) @@ -32816,7 +33809,7 @@ Index (line 43) * sub() function, arguments of: String Functions. (line 460) * sub() function, escape processing: Gory Details. (line 6) -* subscript separators: User-modified. (line 156) +* subscript separators: User-modified. (line 146) * subscripts in arrays, multidimensional: Multidimensional. (line 10) * subscripts in arrays, multidimensional, scanning: Multiscanning. (line 11) @@ -32824,19 +33817,19 @@ Index (line 6) * subscripts in arrays, uninitialized variables as: Uninitialized Subscripts. (line 6) -* SUBSEP variable: User-modified. (line 156) +* SUBSEP variable: User-modified. (line 146) * SUBSEP variable, and multidimensional arrays: Multidimensional. (line 16) -* substitute in string: String Functions. (line 82) +* substitute in string: String Functions. (line 89) * substr: String Functions. (line 479) * substring: String Functions. (line 479) * Sumner, Andrew: Other Versions. (line 64) -* supplementary groups of gawk process: Auto-set. (line 243) +* supplementary groups of gawk process: Auto-set. (line 244) * switch statement: Switch Statement. (line 6) -* SYMTAB array: Auto-set. (line 283) +* SYMTAB array: Auto-set. (line 276) * syntactic ambiguity: /= operator vs. /=.../ regexp constant: Assignment Ops. - (line 147) -* system: I/O Functions. (line 72) + (line 148) +* system: I/O Functions. (line 75) * systime: Time Functions. (line 66) * t debugger command (alias for tbreak): Breakpoint Control. (line 90) * tbreak debugger command: Breakpoint Control. (line 90) @@ -32846,11 +33839,11 @@ Index * tee utility: Tee Program. (line 6) * tee.awk program: Tee Program. (line 26) * temporary breakpoint: Breakpoint Control. (line 90) -* terminating records: Records. (line 132) +* terminating records: awk split records. (line 124) * testbits.awk program: Bitwise Functions. (line 70) * testext extension: Extension Sample API Tests. (line 6) -* Texinfo <1>: Adding Code. (line 99) +* Texinfo <1>: Adding Code. (line 100) * Texinfo <2>: Distribution contents. (line 77) * Texinfo <3>: Extract Program. (line 12) @@ -32863,21 +33856,21 @@ Index * text, printing: Print. (line 22) * text, printing, unduplicated lines of: Uniq Program. (line 6) * TEXTDOMAIN variable <1>: Programmer i18n. (line 9) -* TEXTDOMAIN variable: User-modified. (line 162) +* TEXTDOMAIN variable: User-modified. (line 152) * TEXTDOMAIN variable, BEGIN pattern and: Programmer i18n. (line 60) * TEXTDOMAIN variable, portability and: I18N Portability. (line 20) -* textdomain() function (C library): Explaining gettext. (line 27) +* textdomain() function (C library): Explaining gettext. (line 28) * tilde (~), ~ operator <1>: Expression Patterns. (line 24) * tilde (~), ~ operator <2>: Precedence. (line 80) * tilde (~), ~ operator <3>: Comparison Operators. (line 11) * tilde (~), ~ operator <4>: Regexp Constants. (line 6) -* tilde (~), ~ operator <5>: Computed Regexps. (line 6) -* tilde (~), ~ operator <6>: Case-sensitivity. (line 26) +* tilde (~), ~ operator <5>: Case-sensitivity. (line 26) +* tilde (~), ~ operator <6>: Computed Regexps. (line 6) * tilde (~), ~ operator: Regexp Usage. (line 19) * time functions: Time Functions. (line 6) * time, alarm clock example program: Alarm Program. (line 11) -* time, localization and: Explaining gettext. (line 115) +* time, localization and: Explaining gettext. (line 112) * time, managing: Getlocaltime Function. (line 6) * time, retrieving: Time Functions. (line 17) @@ -32894,38 +33887,37 @@ Index * traceback, display in debugger: Execution Stack. (line 13) * translate string: I18N Functions. (line 22) * translate.awk program: Translate Program. (line 55) -* treating files, as single records: Records. (line 219) -* troubleshooting, --non-decimal-data option: Options. (line 207) +* treating files, as single records: gawk split records. (line 92) +* troubleshooting, --non-decimal-data option: Options. (line 211) * troubleshooting, == operator: Comparison Operators. (line 37) * troubleshooting, awk uses FS not IFS: Field Separators. (line 30) * troubleshooting, backslash before nonspecial character: Escape Sequences. - (line 112) + (line 120) * troubleshooting, division: Arithmetic Ops. (line 44) * troubleshooting, fatal errors, field widths, specifying: Constant Size. (line 23) * troubleshooting, fatal errors, printf format strings: Format Modifiers. (line 159) -* troubleshooting, fflush() function: I/O Functions. (line 60) -* troubleshooting, function call syntax: Function Calls. (line 28) +* troubleshooting, fflush() function: I/O Functions. (line 63) +* troubleshooting, function call syntax: Function Calls. (line 30) * troubleshooting, gawk: Compatibility Mode. (line 6) * troubleshooting, gawk, bug reports: Bugs. (line 9) * troubleshooting, gawk, fatal errors, function arguments: Calling Built-in. (line 16) * troubleshooting, getline function: File Checking. (line 25) * troubleshooting, gsub()/sub() functions: String Functions. (line 470) -* troubleshooting, match() function: String Functions. (line 286) -* troubleshooting, patsplit() function: String Functions. (line 309) +* troubleshooting, match() function: String Functions. (line 289) * troubleshooting, print statement, omitting commas: Print Examples. (line 31) * troubleshooting, printing: Redirection. (line 118) * troubleshooting, quotes with file names: Special FD. (line 68) * troubleshooting, readable data files: File Checking. (line 6) * troubleshooting, regexp constants vs. string constants: Computed Regexps. - (line 38) + (line 39) * troubleshooting, string concatenation: Concatenation. (line 26) * troubleshooting, substr() function: String Functions. (line 497) -* troubleshooting, system() function: I/O Functions. (line 94) +* troubleshooting, system() function: I/O Functions. (line 97) * troubleshooting, typographical errors, global variables: Options. (line 98) * true, logical: Truth Values. (line 6) @@ -32934,14 +33926,14 @@ Index * Trueman, David: History. (line 30) * trunc-mod operation: Arithmetic Ops. (line 66) * truth values: Truth Values. (line 6) -* type conversion: Conversion. (line 21) +* type conversion: Strings And Numbers. (line 21) * u debugger command (alias for until): Debugger Execution Control. (line 83) * unassigned array elements: Reference to Elements. (line 18) * undefined functions: Pass By Value/Reference. (line 71) -* underscore (_), C macro: Explaining gettext. (line 70) +* underscore (_), C macro: Explaining gettext. (line 71) * underscore (_), in names of private variables: Library Names. (line 29) * underscore (_), translatable string: Programmer i18n. (line 69) @@ -32955,21 +33947,21 @@ Index (line 6) * uniq utility: Uniq Program. (line 6) * uniq.awk program: Uniq Program. (line 65) -* Unix: Glossary. (line 616) +* Unix: Glossary. (line 611) * Unix awk, backslashes in escape sequences: Escape Sequences. - (line 124) + (line 132) * Unix awk, close() function and: Close Files And Pipes. - (line 130) + (line 131) * Unix awk, password files, field separators and: Command Line Field Separator. - (line 64) + (line 65) * Unix, awk scripts and: Executable Scripts. (line 6) * UNIXROOT variable, on OS/2 systems: PC Using. (line 16) -* unsigned integers: General Arithmetic. (line 15) +* unsigned integers: Computer Arithmetic. (line 41) * until debugger command: Debugger Execution Control. (line 83) * unwatch debugger command: Viewing And Changing Data. (line 84) -* up debugger command: Execution Stack. (line 33) +* up debugger command: Execution Stack. (line 34) * user database, reading: Passwd Functions. (line 6) * user-defined functions: User-defined. (line 6) * user-defined, functions, counts, in a profile: Profiling. (line 137) @@ -32980,14 +33972,14 @@ Index * USR1 signal, for dynamic profiling: Profiling. (line 188) * values, numeric: Basic Data Typing. (line 13) * values, string: Basic Data Typing. (line 13) -* variable assignments and input files: Other Arguments. (line 19) +* variable assignments and input files: Other Arguments. (line 23) * variable typing: Typing and Comparison. (line 9) * variables <1>: Basic Data Typing. (line 6) * variables: Other Features. (line 6) * variables, assigning on command line: Assignment Options. (line 6) * variables, built-in <1>: Built-in Variables. (line 6) -* variables, built-in: Using Variables. (line 20) +* variables, built-in: Using Variables. (line 23) * variables, built-in, -v option, setting with: Options. (line 40) * variables, built-in, conveying information: Auto-set. (line 6) * variables, flag: Boolean Ops. (line 67) @@ -33000,26 +33992,26 @@ Index * variables, getline command into, using: Getline/Variable. (line 6) * variables, global, for library functions: Library Names. (line 11) * variables, global, printing list of: Options. (line 93) -* variables, initializing: Using Variables. (line 20) +* variables, initializing: Using Variables. (line 23) * variables, local to a function: Variable Scope. (line 6) * variables, names of: Arrays. (line 18) * variables, private: Library Names. (line 11) * variables, setting: Options. (line 32) -* variables, shadowing: Definition Syntax. (line 61) +* variables, shadowing: Definition Syntax. (line 71) * variables, types of: Assignment Ops. (line 40) * variables, types of, comparison expressions and: Typing and Comparison. (line 9) * variables, uninitialized, as array subscripts: Uninitialized Subscripts. (line 6) * variables, user-defined: Variables. (line 6) -* version of gawk: Auto-set. (line 213) -* version of gawk extension API: Auto-set. (line 238) -* version of GNU MP library: Auto-set. (line 224) -* version of GNU MPFR library: Auto-set. (line 220) -* vertical bar (|): Regexp Operators. (line 69) +* version of gawk: Auto-set. (line 214) +* version of gawk extension API: Auto-set. (line 239) +* version of GNU MP library: Auto-set. (line 225) +* version of GNU MPFR library: Auto-set. (line 221) +* vertical bar (|): Regexp Operators. (line 70) * vertical bar (|), | operator (I/O) <1>: Precedence. (line 65) * vertical bar (|), | operator (I/O): Getline/Pipe. (line 9) -* vertical bar (|), |& operator (I/O) <1>: Two-way I/O. (line 44) +* vertical bar (|), |& operator (I/O) <1>: Two-way I/O. (line 25) * vertical bar (|), |& operator (I/O) <2>: Precedence. (line 65) * vertical bar (|), |& operator (I/O): Getline/Coprocess. (line 6) * vertical bar (|), || operator <1>: Precedence. (line 89) @@ -33036,7 +34028,7 @@ Index * Wall, Larry <1>: Future Extensions. (line 6) * Wall, Larry: Array Intro. (line 6) * Wallin, Anders: Contributors. (line 103) -* warnings, issuing: Options. (line 182) +* warnings, issuing: Options. (line 185) * watch debugger command: Viewing And Changing Data. (line 67) * watchpoint: Debugging Terms. (line 42) @@ -33049,7 +34041,7 @@ Index * whitespace, as field separators: Default Field Splitting. (line 6) * whitespace, functions, calling: Calling Built-in. (line 10) -* whitespace, newlines as: Options. (line 253) +* whitespace, newlines as: Options. (line 258) * Williams, Kent: Contributors. (line 34) * Woehlke, Matthew: Contributors. (line 79) * Woods, John: Contributors. (line 27) @@ -33068,26 +34060,25 @@ Index * xgettext utility: String Extraction. (line 13) * xor: Bitwise Functions. (line 55) * XOR bitwise operation: Bitwise Functions. (line 6) -* Yawitz, Efraim: Contributors. (line 129) -* Zaretskii, Eli <1>: Bugs. (line 70) +* Yawitz, Efraim: Contributors. (line 131) +* Zaretskii, Eli <1>: Bugs. (line 71) * Zaretskii, Eli <2>: Contributors. (line 55) * Zaretskii, Eli: Acknowledgments. (line 60) -* zero, negative vs. positive: Unexpected Results. (line 34) * zerofile.awk program: Empty Files. (line 21) * Zoulas, Christos: Contributors. (line 66) * {} (braces): Profiling. (line 142) * {} (braces), actions and: Action Overview. (line 19) * {} (braces), statements, grouping: Statements. (line 10) -* | (vertical bar): Regexp Operators. (line 69) +* | (vertical bar): Regexp Operators. (line 70) * | (vertical bar), | operator (I/O) <1>: Precedence. (line 65) * | (vertical bar), | operator (I/O) <2>: Redirection. (line 57) * | (vertical bar), | operator (I/O): Getline/Pipe. (line 9) -* | (vertical bar), |& operator (I/O) <1>: Two-way I/O. (line 44) +* | (vertical bar), |& operator (I/O) <1>: Two-way I/O. (line 25) * | (vertical bar), |& operator (I/O) <2>: Precedence. (line 65) * | (vertical bar), |& operator (I/O) <3>: Redirection. (line 102) * | (vertical bar), |& operator (I/O): Getline/Coprocess. (line 6) * | (vertical bar), |& operator (I/O), pipes, closing: Close Files And Pipes. - (line 118) + (line 119) * | (vertical bar), || operator <1>: Precedence. (line 89) * | (vertical bar), || operator: Boolean Ops. (line 57) * ~ (tilde), ~ operator <1>: Expression Patterns. (line 24) @@ -33095,537 +34086,561 @@ Index * ~ (tilde), ~ operator <3>: Comparison Operators. (line 11) * ~ (tilde), ~ operator <4>: Regexp Constants. (line 6) -* ~ (tilde), ~ operator <5>: Computed Regexps. (line 6) -* ~ (tilde), ~ operator <6>: Case-sensitivity. (line 26) +* ~ (tilde), ~ operator <5>: Case-sensitivity. (line 26) +* ~ (tilde), ~ operator <6>: Computed Regexps. (line 6) * ~ (tilde), ~ operator: Regexp Usage. 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Inplace1023685 +Node: Extension Sample Ord1025360 +Node: Extension Sample Readdir1026196 +Ref: table-readdir-file-types1027052 +Node: Extension Sample Revout1027851 +Node: Extension Sample Rev2way1028442 +Node: Extension Sample Read write array1029183 +Node: Extension Sample Readfile1031062 +Node: Extension Sample API Tests1032162 +Node: Extension Sample Time1032687 +Node: gawkextlib1034002 +Node: Extension summary1036815 +Node: Extension Exercises1040508 +Node: Language History1041230 +Node: V7/SVR3.11042873 +Node: SVR41045193 +Node: POSIX1046635 +Node: BTL1048021 +Node: POSIX/GNU1048755 +Node: Feature History1054531 +Node: Common Extensions1067622 +Node: Ranges and Locales1068934 +Ref: Ranges and Locales-Footnote-11073551 +Ref: Ranges and Locales-Footnote-21073578 +Ref: Ranges and Locales-Footnote-31073812 +Node: Contributors1074033 +Node: History summary1079458 +Node: Installation1080827 +Node: Gawk Distribution1081778 +Node: Getting1082262 +Node: Extracting1083086 +Node: Distribution contents1084728 +Node: Unix Installation1090498 +Node: Quick Installation1091115 +Node: Additional Configuration Options1093557 +Node: Configuration Philosophy1095295 +Node: Non-Unix Installation1097646 +Node: PC Installation1098104 +Node: PC Binary Installation1099415 +Node: PC Compiling1101263 +Ref: PC Compiling-Footnote-11104262 +Node: PC Testing1104367 +Node: PC Using1105543 +Node: Cygwin1109695 +Node: MSYS1110504 +Node: VMS Installation1111018 +Node: VMS Compilation1111814 +Ref: VMS Compilation-Footnote-11113036 +Node: VMS Dynamic Extensions1113094 +Node: VMS Installation Details1114467 +Node: VMS Running1116719 +Node: VMS GNV1119553 +Node: VMS Old Gawk1120276 +Node: Bugs1120746 +Node: Other Versions1124750 +Node: Installation summary1130974 +Node: Notes1132030 +Node: Compatibility Mode1132895 +Node: Additions1133677 +Node: Accessing The Source1134602 +Node: Adding Code1136038 +Node: New Ports1142216 +Node: Derived Files1146697 +Ref: Derived Files-Footnote-11152172 +Ref: Derived Files-Footnote-21152206 +Ref: Derived Files-Footnote-31152802 +Node: Future Extensions1152916 +Node: Implementation Limitations1153522 +Node: Extension Design1154770 +Node: Old Extension Problems1155924 +Ref: Old Extension Problems-Footnote-11157441 +Node: Extension New Mechanism Goals1157498 +Ref: Extension New Mechanism Goals-Footnote-11160858 +Node: Extension Other Design Decisions1161047 +Node: Extension Future Growth1163153 +Node: Old Extension Mechanism1163989 +Node: Notes summary1165751 +Node: Basic Concepts1166937 +Node: Basic High Level1167618 +Ref: figure-general-flow1167890 +Ref: figure-process-flow1168489 +Ref: Basic High Level-Footnote-11171718 +Node: Basic Data Typing1171903 +Node: Glossary1175231 +Node: Copying1200383 +Node: GNU Free Documentation License1237939 +Node: Index1263075 End Tag Table |