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diff --git a/doc/gawk.info b/doc/gawk.info index e39a483b..0ac376a0 100644 --- a/doc/gawk.info +++ b/doc/gawk.info @@ -1,18 +1,17 @@ -This is Info file gawk.info, produced by Makeinfo version 1.68 from the -input file ./gawk.texi. +This is gawk.info, produced by makeinfo version 4.0 from ./gawk.texi. INFO-DIR-SECTION Programming Languages START-INFO-DIR-ENTRY -* Gawk: (gawk.info). A Text Scanning and Processing Language. +* Gawk: (gawk). A Text Scanning and Processing Language. END-INFO-DIR-ENTRY This file documents `awk', a program that you can use to select particular records in a file and perform operations upon them. - This is Edition 1.0.4 of `Effective AWK Programming', for the -3.0.4 version of the GNU implementation of AWK. + This is Edition 1.0.5 of `Effective AWK Programming', for the +3.0.5 version of the GNU implementation of AWK. - Copyright (C) 1989, 1991, 92, 93, 96, 97, 98, 99 Free Software + Copyright (C) 1989, 1991, 1992, 1993, 1996-2000 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this @@ -38,8 +37,8 @@ General Introduction This file documents `awk', a program that you can use to select particular records in a file and perform operations upon them. - This is Edition 1.0.4 of `Effective AWK Programming', -for the 3.0.4 version of the GNU implementation + This is Edition 1.0.5 of `Effective AWK Programming', +for the 3.0.5 version of the GNU implementation of AWK. * Menu: @@ -173,13 +172,13 @@ of AWK. * Concatenation:: Concatenating strings. * Assignment Ops:: Changing the value of a variable or a field. * Increment Ops:: Incrementing the numeric value of a variable. -* Truth Values:: What is "true" and what is "false". +* Truth Values:: What is ``true'' and what is ``false''. * Typing and Comparison:: How variables acquire types, and how this affects comparison of numbers and strings with `<', etc. * Boolean Ops:: Combining comparison expressions using boolean - operators `||' ("or"), `&&' - ("and") and `!' ("not"). + operators `||' (``or''), `&&' + (``and'') and `!' (``not''). * Conditional Exp:: Conditional expressions select between two subexpressions under control of a third subexpression. @@ -316,7 +315,7 @@ of AWK. * Time Functions Summary:: Built-in time functions. * String Constants Summary:: Escape sequences in strings. * Functions Summary:: Defining and calling functions. -* Historical Features:: Some undocumented but supported "features". +* Historical Features:: Some undocumented but supported ``features''. * Gawk Distribution:: What is in the `gawk' distribution. * Getting:: How to get the distribution. * Extracting:: How to extract the distribution. @@ -348,12 +347,18 @@ of AWK. To Miriam, for making me complete. + To Chana, for the joy you bring us. + To Rivka, for the exponential increase. + To Nachum, for the added dimension. + + To Malka, for the new beginning. + File: gawk.info, Node: Preface, Next: What Is Awk, Prev: Top, Up: Top @@ -512,7 +517,7 @@ Pat Rankin, Michal Jaegermann, Darrel Hankerson and Scott Deifik updated their respective sections for Edition 1.0. Robert J. Chassell provided much valuable advice on the use of -Texinfo. He also deserves special thanks for convincing me *not* to +Texinfo. He also deserves special thanks for convincing me _not_ to title this Info file `How To Gawk Politely'. Karl Berry helped significantly with the TeX part of Texinfo. @@ -552,6 +557,8 @@ I 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 Atlanta, Georgia February, 1997 @@ -639,7 +646,7 @@ Library of `awk' Functions: Library Functions.; also *note Practical your memory about a particular feature. If you find terms that you aren't familiar with, try looking them up -in the glossary (*note Glossary::.). +in the glossary (*note Glossary::). Most of the time complete `awk' programs are used as examples, but in some of the more advanced sections, only the part of the `awk' program @@ -658,6 +665,8 @@ Dark Corners Who opened that window shade?!? Count Dracula + + Until the POSIX standard (and `The Gawk Manual'), many features of `awk' were either poorly documented, or not documented at all. Descriptions of such features (often called "dark corners") are noted @@ -1043,7 +1052,7 @@ like this: : The colon ensures execution by the standard shell. awk 'PROGRAM' "$@" - Using this technique, it is *vital* to enclose the PROGRAM in single + Using this technique, it is _vital_ to enclose the PROGRAM in single quotes to protect it from interpretation by the shell. If you omit the quotes, only a shell wizard can predict the results. @@ -1097,7 +1106,7 @@ later time. *Caution:* As mentioned in *Note One-shot Throw-away `awk' Programs: One-shot, you can enclose small to medium programs in single quotes, in order to keep your shell scripts self-contained. When doing so, -*don't* put an apostrophe (i.e., a single quote) into a comment (or +_don't_ put an apostrophe (i.e., a single quote) into a comment (or anywhere else in your program). The shell will interpret the quote as the closing quote for the entire program. As a result, usually the shell will print a message about mismatched quotes, and if `awk' @@ -1142,7 +1151,7 @@ special shell characters. In an `awk' rule, either the pattern or the action can be omitted, but not both. If the pattern is omitted, then the action is performed -for *every* input line. If the action is omitted, the default action +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 @@ -1179,7 +1188,7 @@ the pattern and also has `print $0' as the action. Each rule's action is enclosed in its own pair of braces. This `awk' program prints every line that contains the string `12' -*or* the string `21'. If a line contains both strings, it is printed +_or_ the string `21'. If a line contains both strings, it is printed twice, once by each rule. This is what happens if we run this program on our two sample data @@ -1315,11 +1324,11 @@ expression or a string. *Caution: backslash continuation does not work as described above with the C shell.* Continuation with backslash works for `awk' -programs in files, and also for one-shot programs *provided* you are +programs in files, and also for one-shot programs _provided_ you are using a POSIX-compliant shell, such as the Bourne shell or Bash, the GNU Bourne-Again shell. But the C shell (`csh') behaves differently! There, you must use two backslashes in a row, followed by a newline. -Note also that when using the C shell, *every* newline in your awk +Note also that when using the C shell, _every_ newline in your awk program must be escaped with a backslash. To illustrate: % awk 'BEGIN { \ @@ -1333,11 +1342,11 @@ analogous to the standard shell's `$' and `>'. `awk' is a line-oriented language. Each rule's action has to begin on the same line as the pattern. To have the pattern and action on -separate lines, you *must* use backslash continuation--there is no +separate lines, you _must_ use backslash continuation--there is no other way. Note that backslash continuation and comments do not mix. As soon as -`awk' sees the `#' that starts a comment, it ignores *everything* on +`awk' sees the `#' that starts a comment, it ignores _everything_ on the rest of the line. For example: $ gawk 'BEGIN { print "dont panic" # a friendly \ @@ -1405,10 +1414,10 @@ can avoid the (usually lengthy) compilation part of the typical edit-compile-test-debug cycle of software development. Complex programs have been written in `awk', including a complete -retargetable assembler for eight-bit microprocessors (*note -Glossary::., for more information) and a microcode assembler for a -special purpose Prolog computer. However, `awk''s capabilities are -strained by tasks of such complexity. +retargetable assembler for eight-bit microprocessors (*note Glossary::, +for more information) and a microcode assembler for a special purpose +Prolog computer. However, `awk''s capabilities are strained by tasks of +such complexity. If you find yourself writing `awk' scripts of more than, say, a few hundred lines, you might consider using a different programming @@ -1506,7 +1515,7 @@ that matches every input record whose text belongs to that set. 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 -characters `foo', *anywhere* in the record. Other kinds of regexps let +characters `foo', _anywhere_ in the record. Other kinds of regexps let you specify more complicated classes of strings. * Menu: @@ -1562,8 +1571,8 @@ statements. (*Note Control Statements in Actions: Statements.) `EXP !~ /REGEXP/' This is true if the expression EXP (taken as a character string) - is *not* matched by REGEXP. The following example matches, or - selects, all input records whose first field *does not* contain + is _not_ matched by REGEXP. The following example matches, or + selects, all input records whose first field _does not_ contain the upper-case letter `J': $ awk '$1 !~ /J/' inventory-shipped @@ -1768,7 +1777,7 @@ themselves. if ("line1\nLINE 2" ~ /1$/) ... `.' - The period, or dot, matches any single character, *including* the + The period, or dot, matches any single character, _including_ the newline character. For example: .P @@ -1784,7 +1793,7 @@ themselves. Other versions of `awk' may not be able to match the NUL character. `[...]' - This is called a "character list". It matches any *one* of the + This is called a "character list". It matches any _one_ of the characters that are enclosed in the square brackets. For example: [MVX] @@ -1822,7 +1831,7 @@ themselves. notion of what is an alphabetic character differs in the USA and in France. - A character class is only valid in a regexp *inside* the brackets + A character class is only valid in a regexp _inside_ the brackets of a character list. Character classes consist of `[:', a keyword denoting the class, and `:]'. Here are the character classes defined by the POSIX standard. @@ -1871,7 +1880,7 @@ themselves. characters, you had to write `/[A-Za-z0-9]/'. If your character set had other alphabetic characters in it, this would not match them. With the POSIX character classes, you can write - `/[[:alnum:]]/', and this will match *all* the alphabetic and + `/[[:alnum:]]/', and this will match _all_ the alphabetic and numeric characters in your character set. Two additional special sequences can appear in character lists. @@ -1879,7 +1888,7 @@ themselves. symbols (called "collating elements") that are represented with more than one character, as well as several characters that are equivalent for "collating", or sorting, purposes. (E.g., in - French, a plain "e" and a grave-accented "`e" are equivalent.) + French, a plain "e" and a grave-accented "e`" are equivalent.) Collating Symbols A "collating symbol" is a multi-character collating element @@ -1892,8 +1901,8 @@ themselves. An "equivalence class" is a locale-specific name for a list of characters that are equivalent. The name is enclosed in `[=' and `=]'. For example, the name `e' might be used to - represent all of "e," "`e," and "'e." In this case, `[[=e]]' - is a regexp that matches any of `e', `'e', or ``e'. + represent all of "e," "e`," and "e'." In this case, `[[=e]]' + is a regexp that matches any of `e', `e'', or `e`'. These features are very valuable in non-English speaking locales. @@ -1904,7 +1913,7 @@ themselves. `[^ ...]' This is a "complemented character list". The first character after - the `[' *must* be a `^'. It matches any characters *except* those + the `[' _must_ be a `^'. It matches any characters _except_ those in the square brackets. For example: [^0-9] @@ -1942,7 +1951,7 @@ themselves. of one `p' followed by any number of `h's. This will also match just `p' if no `h's are present. - The `*' repeats the *smallest* possible preceding expression. + The `*' repeats the _smallest_ possible preceding expression. (Use parentheses if you wish to repeat a larger expression.) It finds as many repetitions as possible. For example: @@ -1996,7 +2005,7 @@ themselves. `egrep' consistent with each other. However, since old programs may use `{' and `}' in regexp - constants, by default `gawk' does *not* match interval expressions + constants, by default `gawk' does _not_ match interval expressions in regexps. If either `--posix' or `--re-interval' are specified (*note Command Line Options: Options.), then interval expressions are allowed in regexps. @@ -2087,7 +2096,7 @@ of two evils. Options.) control how `gawk' interprets characters in regexps. No options - In the default case, `gawk' provide all the facilities of POSIX + In the default case, `gawk' provides all the facilities of POSIX regexps and the GNU regexp operators described in *Note Regular Expression Operators: Regexp Operators. However, interval expressions are not supported. @@ -2136,8 +2145,8 @@ converts the first field to lower-case before matching against it. This will work in any POSIX-compliant implementation of `awk'. Another method, specific to `gawk', is to set the variable -`IGNORECASE' to a non-zero value (*note Built-in Variables::.). When -`IGNORECASE' is not zero, *all* regexp and string operations ignore +`IGNORECASE' to a non-zero 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 sensitivity of your program as it runs. Case is significant by default because `IGNORECASE' (like most variables) is initialized to zero. @@ -2196,20 +2205,20 @@ In other words, how many is "one or more"--will `awk' match two, three, or all four `a' characters? The answer is, `awk' (and POSIX) regular expressions always match -the leftmost, *longest* sequence of input characters that can match. +the leftmost, _longest_ sequence of input characters that can match. Thus, in this example, all four `a' characters are replaced with `<A>'. $ echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' -| <A>bcd For simple match/no-match tests, this is not so important. But when -doing regexp-based field and record splitting, and text matching and -substitutions with the `match', `sub', `gsub', and `gensub' functions, -it is very important. *Note Built-in Functions for String -Manipulation: String Functions, for more information on these functions. -Understanding this principle is also important for regexp-based record -and field splitting (*note How Input is Split into Records: Records., -and also *note Specifying How Fields are Separated: Field Separators.). +doing text matching and substitutions with the `match', `sub', `gsub', +and `gensub' functions, it is very important. *Note Built-in Functions +for String Manipulation: String Functions, for more information on +these functions. Understanding this principle is also important for +regexp-based record and field splitting (*note How Input is Split into +Records: Records., and also *note Specifying How Fields are Separated: +Field Separators.). File: gawk.info, Node: Computed Regexps, Prev: Leftmost Longest, Up: Regexp @@ -2223,7 +2232,7 @@ expression. The expression is evaluated, and converted if necessary to a string; the contents of the string are used as the regexp. A regexp that is computed in this way is called a "dynamic regexp". For example: - BEGIN { identifier_regexp = "[A-Za-z_][A-Za-z_0-9]+" } + BEGIN { identifier_regexp = "[A-Za-z_][A-Za-z_0-9]*" } $0 ~ identifier_regexp { print } sets `identifier_regexp' to a regexp that describes `awk' variable @@ -2233,7 +2242,7 @@ names, and tests if the input record matches this regexp. 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 +_twice_; the first time when `awk' reads your program, and the second time when it goes to match the string on the left-hand side of the operator with the pattern on the right. This is true of any string valued expression (such as `identifier_regexp' above), not just string @@ -2279,7 +2288,7 @@ command) or from files whose names you specify on the `awk' command line. If you specify input files, `awk' reads them in order, reading all the data from one before going on to the next. The name of the current input file can be found in the built-in variable `FILENAME' -(*note Built-in Variables::.). +(*note Built-in Variables::). The input is read in units called "records", and processed by the rules of your program one record at a time. By default, each record is @@ -2469,7 +2478,7 @@ separated or "parsed" by the interpreter into chunks called "fields". By default, fields are separated by whitespace, like words in a line. Whitespace in `awk' means any string of one or more spaces, tabs or newlines;(1) other characters such as formfeed, and so on, that are -considered whitespace by other languages are *not* considered +considered whitespace by other languages are _not_ considered whitespace by `awk'. The purpose of fields is to make it more convenient for you to refer @@ -2518,8 +2527,8 @@ field contains the string `foo'. The operator `~' is called a Usage.); it tests whether a string (here, the field `$1') matches a given regular expression. - By contrast, the following example looks for `foo' in *the entire -record* and prints the first field and the last field for each input + By contrast, the following example looks for `foo' in _the entire +record_ and prints the first field and the last field for each input record containing a match. $ awk '/foo/ { print $1, $NF }' BBS-list @@ -2577,7 +2586,7 @@ behave differently.) As mentioned in *Note Examining Fields: Fields, the number of fields in the current record is stored in the built-in variable `NF' (also -*note Built-in Variables::.). The expression `$NF' is not a special +*note Built-in 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. @@ -2589,7 +2598,7 @@ Changing the Contents of a Field You can change the contents of a field as seen by `awk' within an `awk' program; this changes what `awk' perceives as the current input -record. (The actual input is untouched; `awk' *never* modifies the +record. (The actual input is untouched; `awk' _never_ modifies the input file.) Consider this example and its output: @@ -2648,11 +2657,11 @@ existing fields. This recomputation affects and is affected by `NF' (the number of fields; *note Examining Fields: Fields.), and by a feature that has not been discussed yet, the "output field separator", `OFS', which is used -to separate the fields (*note Output Separators::.). For example, the +to separate the fields (*note Output Separators::). For example, the value of `NF' is set to the number of the highest field you create. - Note, however, that merely *referencing* an out-of-range field does -*not* change the value of either `$0' or `NF'. Referencing an + Note, however, that merely _referencing_ an out-of-range field does +_not_ change the value of either `$0' or `NF'. Referencing an out-of-range field only produces an empty string. For example: if ($(NF+1) != "") @@ -2738,7 +2747,7 @@ would be split into three fields: `m', `*g' and `*gai*pan'. Note the leading spaces in the values of the second and third fields. The field separator is represented by the built-in variable `FS'. -Shell programmers take note! `awk' does *not* use the name `IFS' which +Shell programmers take note! `awk' does _not_ use the name `IFS' which is used by the POSIX compatible shells (such as the Bourne shell, `sh', or the GNU Bourne-Again Shell, Bash). @@ -2805,7 +2814,7 @@ example, the assignment: makes every area of an input line that consists of a comma followed by a space and a tab, into a field separator. (`\t' is an "escape sequence" -that stands for a tab; *note Escape Sequences::., for the complete list +that stands for a tab; *note Escape Sequences::, for the complete list of similar escape sequences.) For a less trivial example of a regular expression, suppose you want @@ -2893,7 +2902,7 @@ capital `F'. Contrast this with `-f', which specifies a file containing an `awk' program. Case is significant in command line options: the `-F' and `-f' options have nothing to do with each other. You can use both options at the same time to set the `FS' variable -*and* get an `awk' program from a file. +_and_ get an `awk' program from a file. The value used for the argument to `-F' is processed in exactly the same way as assignments to the built-in variable `FS'. This means that @@ -2906,7 +2915,7 @@ would have to type: Since `\' is used for quoting in the shell, `awk' will see `-F\\'. Then `awk' processes the `\\' for escape characters (*note Escape -Sequences::.), finally yielding a single `\' to be used for the field +Sequences::), finally yielding a single `\' to be used for the field separator. As a special case, in compatibility mode (*note Command Line @@ -2971,7 +2980,7 @@ should reflect the old value of `FS', not the new one. However, many implementations of `awk' do not work this way. Instead, they defer splitting the fields until a field is actually -referenced. The fields will be split using the *current* value of +referenced. The fields will be split using the _current_ value of `FS'! (d.c.) This behavior can be difficult to diagnose. The following example illustrates the difference between the two methods. (The `sed'(1) command prints just the first line of `/etc/passwd'.) @@ -3029,8 +3038,8 @@ numbers are run together; or in the output of programs that did not anticipate the use of their output as input for other programs. An example of the latter is a table where all the columns are lined -up by the use of a variable number of spaces and *empty fields are just -spaces*. Clearly, `awk''s normal field splitting based on `FS' will +up by the use of a variable number of spaces and _empty fields are just +spaces_. Clearly, `awk''s normal field splitting based on `FS' will not work well in this case. Although a portable `awk' program can use a series of `substr' calls on `$0' (*note Built-in Functions for String Manipulation: String Functions.), this is awkward and inefficient for a @@ -3039,7 +3048,7 @@ large number of fields. The splitting of an input record into fixed-width fields is specified by assigning a string containing space-separated numbers to the built-in variable `FIELDWIDTHS'. Each number specifies the width -of the field *including* columns between fields. If you want to ignore +of the field _including_ columns between fields. If you want to ignore the columns between fields, you can specify the width as a separate field that is subsequently ignored. @@ -3155,7 +3164,7 @@ second case, this special processing is not done (d.c.). separate the fields in the record. One way to do this is to divide each of the lines into fields in the normal manner. This happens by default as the result of a special feature: when `RS' is set to the empty -string, the newline character *always* acts as a field separator. This +string, the newline character _always_ acts as a field separator. This is in addition to whatever field separations result from `FS'. The original motivation for this special exception was probably to @@ -3181,7 +3190,6 @@ a mailing list in a file named `addresses', that looks like this: John Smith 456 Tree-lined Avenue Smallville, MW 98765-4321 - ... A simple program to process this file would look like this: @@ -3272,11 +3280,11 @@ File: gawk.info, Node: Getline Intro, Next: Plain Getline, Prev: Getline, Up Introduction to `getline' ------------------------- - This command is used in several different ways, and should *not* be + This command is used in several different ways, and should _not_ be used by beginners. It is covered here because this is the chapter on input. The examples that follow the explanation of the `getline' command include material that has not been covered yet. Therefore, -come back and study the `getline' command *after* you have reviewed the +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. `getline' returns one if it finds a record, and zero if the end of @@ -3298,7 +3306,7 @@ Using `getline' with No Arguments from the current input file. All it does in this case is read the next input record and split it up into fields. This is useful if you've finished processing the current record, but you want to do some special -processing *right now* on the next record. Here's an example: +processing _right now_ on the next record. Here's an example: awk '{ if ((t = index($0, "/*")) != 0) { @@ -3658,10 +3666,10 @@ relational operator; otherwise it could be confused with a redirection of the current record (such as `$1'), variables, or any `awk' expressions. Numeric values are converted to strings, and then printed. - The `print' statement is completely general for computing *what* -values to print. However, with two exceptions, you cannot specify *how* + The `print' statement is completely general for computing _what_ +values to print. However, with two exceptions, you cannot specify _how_ to print them--how many columns, whether to use exponential notation or -not, and so on. (For the exceptions, *note Output Separators::., and +not, and so on. (For the exceptions, *note Output Separators::, and *Note Controlling Numeric Output with `print': OFMT.) For that, you need the `printf' statement (*note Using `printf' Statements for Fancier Printing: Printf.). @@ -3689,7 +3697,7 @@ Examples of `print' Statements Here is an example of printing a string that contains embedded newlines (the `\n' is an escape sequence, used to represent the newline -character; *note Escape Sequences::.): +character; *note Escape Sequences::): $ awk 'BEGIN { print "line one\nline two\nline three" }' -| line one @@ -3954,6 +3962,11 @@ parameters to use, such as the field width. `s' This prints a string. +`u' + This prints an unsigned decimal number. (This format is of + marginal use, since all numbers in `awk' are floating point. It + is provided primarily for compatibility with C.) + `x' `X' This prints an unsigned hexadecimal integer. (In hexadecimal, or @@ -4180,7 +4193,7 @@ for `printf' also. This type of redirection prints the items into the output file OUTPUT-FILE. The file name OUTPUT-FILE can be any expression. Its value is changed to a string and then used as a file name - (*note Expressions::.). + (*note Expressions::). When this type of redirection is used, the OUTPUT-FILE is erased before the first output is written to it. Subsequent writes to @@ -4385,10 +4398,10 @@ these file names is done by `gawk' itself. For example, using `/dev/fd/4' for output will actually write on file descriptor 4, and not on a new file descriptor that was `dup''ed from file descriptor 4. Most of the time this does not matter; however, it is important to -*not* close any of the files related to file descriptors 0, 1, and 2. +_not_ close any of the files related to file descriptors 0, 1, and 2. If you do close one of these files, unpredictable behavior will result. - The special files that provide process-related information may + The special files that provide process-related information will disappear in a future version of `gawk'. *Note Probable Future Extensions: Future Extensions. @@ -4423,7 +4436,7 @@ or close(COMMAND) The argument FILENAME or COMMAND can be any expression. Its value -must *exactly* match the string that was used to open the file or start +must _exactly_ match the string that was used to open the file or start the command (spaces and other "irrelevant" characters included). For example, if you open a pipe with this: @@ -4518,13 +4531,13 @@ calls, as well as combinations of these with various operators. * Concatenation:: Concatenating strings. * Assignment Ops:: Changing the value of a variable or a field. * Increment Ops:: Incrementing the numeric value of a variable. -* Truth Values:: What is "true" and what is "false". +* Truth Values:: What is ``true'' and what is ``false''. * Typing and Comparison:: How variables acquire types, and how this affects comparison of numbers and strings with `<', etc. * Boolean Ops:: Combining comparison expressions using boolean - operators `||' ("or"), `&&' - ("and") and `!' ("not"). + operators `||' (``or''), `&&' + (``and'') and `!' (``not''). * Conditional Exp:: Conditional expressions select between two subexpressions under control of a third subexpression. @@ -4777,7 +4790,7 @@ the `awk' program in an array named `ARGV' (*note Using `ARGC' and `ARGV': ARGC and ARGV.). `awk' processes the values of command line assignments for escape -sequences (d.c.) (*note Escape Sequences::.). +sequences (d.c.) (*note Escape Sequences::). File: gawk.info, Node: Conversion, Next: Arithmetic Ops, Prev: Variables, Up: Expressions @@ -4811,14 +4824,14 @@ interpreted as valid numbers are converted to zero. The exact manner in which numbers are converted into strings is controlled by the `awk' built-in variable `CONVFMT' (*note Built-in -Variables::.). Numbers are converted using the `sprintf' function +Variables::). Numbers are converted using the `sprintf' function (*note Built-in Functions for String Manipulation: String Functions.) with `CONVFMT' as the format specifier. `CONVFMT''s default value is `"%.6g"', which prints a value with at least six significant digits. For some applications you will want to -change it to specify more precision. Double precision on most modern -machines gives you 16 or 17 decimal digits of precision. +change it to specify more precision. On most modern machines, you must +print 17 digits to capture a floating point number's value exactly. Strange results can happen if you set `CONVFMT' to a string that doesn't tell `sprintf' how to format floating point numbers in a useful @@ -4826,7 +4839,7 @@ way. For example, if you forget the `%' in the format, all numbers will be converted to the same constant string. As a special case, if a number is an integer, then the result of -converting it to a string is *always* an integer, no matter what the +converting it to a string is _always_ an integer, no matter what the value of `CONVFMT' may be. Given the following code fragment: CONVFMT = "%2.2f" @@ -4855,7 +4868,9 @@ Arithmetic Operators The `awk' language uses the common arithmetic operators when evaluating expressions. All of these arithmetic operators follow normal -precedence rules, and work as you would expect them to. +precedence rules, and work as you would expect them to. Arithmetic +operations are evaluated using double precision floating point, which +has the usual problems of inexactness and exceptions.(1) Here is a file `grades' containing a list of student names and three test scores per student (it's a small class): @@ -4892,8 +4907,9 @@ highest precedence to lowest: Multiplication. `X / Y' - Division. Since all numbers in `awk' are real numbers, the result - is not rounded to an integer: `3 / 4' has the value 0.75. + Division. Since all numbers in `awk' are floating point numbers, + the result is not rounded to an integer: `3 / 4' has the value + 0.75. `X % Y' Remainder. The quotient is rounded toward zero to an integer, @@ -4923,6 +4939,12 @@ highest precedence to lowest: operators all have the same precedence, and addition and subtraction have the same precedence. + ---------- Footnotes ---------- + + (1) David Goldberg, `What Every Computer Scientist Should Know About +Floating-point Arithmetic' (http://www.validgh.com/goldberg/paper.ps), +`ACM Computing Surveys' *23*, 1 (1991-03), 5-48. + File: gawk.info, Node: Concatenation, Next: Assignment Ops, Prev: Arithmetic Ops, Up: Expressions @@ -4932,6 +4954,8 @@ String Concatenation It seemed like a good idea at the time. Brian Kernighan + + There is only one string operation: concatenation. It does not have a specific operator to represent it. Instead, concatenation is performed by writing expressions next to one another, with no operator. @@ -5002,7 +5026,7 @@ makes itself felt through the alteration of the variable. We call this a "side effect". The left-hand operand of an assignment need not be a variable (*note -Variables::.); it can also be a field (*note Changing the Contents of a +Variables::); it can also be a field (*note Changing the Contents of a Field: Changing Fields.) or an array element (*note Arrays in `awk': Arrays.). These are all called "lvalues", which means they can appear on the left-hand side of an assignment operator. The right-hand @@ -5010,7 +5034,7 @@ operand may be any expression; it produces the new value which 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. + It is important to note that variables do _not_ have permanent types. The type of a variable 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: @@ -5031,7 +5055,7 @@ zero. After executing this code, the value of `foo' is five: (Note that using a variable as a number and then later as a string can be confusing and is poor programming style. The above examples -illustrate how `awk' works, *not* how you should write your own +illustrate how `awk' works, _not_ how you should write your own programs!) An assignment is an expression, so it has a value: the same value @@ -5066,7 +5090,7 @@ This is equivalent to the following: Use whichever one makes the meaning of your program clearer. There are situations where using `+=' (or any assignment operator) -is *not* the same as simply repeating the left-hand operand in the +is _not_ the same as simply repeating the left-hand operand in the right-hand expression. For example: # Thanks to Pat Rankin for this example @@ -5086,7 +5110,7 @@ will return different values each time it is called. (Arrays and the Arrays, and see *Note Numeric Built-in Functions: Numeric Functions, for more information). This example illustrates an important fact about the assignment operators: the left-hand expression is only -evaluated *once*. +evaluated _once_. It is also up to the implementation as to which expression is evaluated first, the left-hand one or the right-hand one. Consider @@ -5145,7 +5169,7 @@ 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. +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. @@ -5173,7 +5197,7 @@ lvalue to pre-decrement or after it to post-decrement. `LVALUE++' This expression increments LVALUE, but the value of the expression - is the *old* value of LVALUE. + is the _old_ value of LVALUE. `--LVALUE' Like `++LVALUE', but instead of adding, it subtracts. It @@ -5181,7 +5205,7 @@ lvalue to pre-decrement or after it to post-decrement. `LVALUE--' Like `LVALUE++', but instead of adding, it subtracts. It - decrements LVALUE. The value of the expression is the *old* value + decrements LVALUE. The value of the expression is the _old_ value of LVALUE. @@ -5195,7 +5219,7 @@ concepts of "true" and "false." Such languages usually use the special constants `true' and `false', or perhaps their upper-case equivalents. `awk' is different. It borrows a very simple concept of true and -false from C. In `awk', any non-zero numeric value, *or* any non-empty +false from C. In `awk', any non-zero numeric value, _or_ any non-empty string value is true. Any other value (zero or the null string, `""') is false. The following program will print `A strange truth value' three times: @@ -5221,6 +5245,8 @@ Variable Typing and Comparison Expressions The Guide is definitive. Reality is frequently inaccurate. The Hitchhiker's Guide to the Galaxy + + Unlike other programming languages, `awk' variables do not have a fixed type. Instead, they can be either a number or a string, depending upon the value that is assigned to them. @@ -5275,7 +5301,7 @@ according to the following, symmetric, matrix: STRNUM | string numeric numeric --------+---------------------------------------------- - The basic idea is that user input that looks numeric, and *only* + The basic idea is that user input that looks numeric, and _only_ user input, should be treated as numeric, even though it is actually made of characters, and is therefore also a string. @@ -5397,7 +5423,7 @@ abbreviation for this comparison expression: $0 ~ /REGEXP/ - One special place where `/foo/' is *not* an abbreviation for `$0 ~ + One special place where `/foo/' is _not_ an abbreviation for `$0 ~ /foo/' is when it is the right-hand operand of `~' or `!~'! *Note Using Regular Expression Constants: Using Constant Regexps, where this is discussed in more detail. @@ -5443,7 +5469,7 @@ you can use one as a pattern to control the execution of rules. `BOOLEAN1 || BOOLEAN2' True if at least one of BOOLEAN1 or BOOLEAN2 is true. For example, the following statement prints all records in the input - that contain *either* `2400' or `foo', or both. + that contain _either_ `2400' or `foo', or both. if ($0 ~ /2400/ || $0 ~ /foo/) print @@ -5453,7 +5479,7 @@ you can use one as a pattern to control the execution of rules. `! BOOLEAN' True if BOOLEAN is false. For example, the following program - prints all records in the input file `BBS-list' that do *not* + prints all records in the input file `BBS-list' that do _not_ contain the string `foo'. awk '{ if (! ($0 ~ /foo/)) print }' BBS-list @@ -5512,9 +5538,9 @@ value becomes the value of the whole expression. x > 0 ? x : -x Each time the conditional expression is computed, exactly one of -IF-TRUE-EXP and IF-FALSE-EXP is computed; the other is ignored. This -is important when the expressions contain side effects. For example, -this conditional expression examines element `i' of either array `a' or +IF-TRUE-EXP and IF-FALSE-EXP is used; the other is ignored. This is +important when the expressions have side effects. For example, this +conditional expression examines element `i' of either array `a' or array `b', and increments `i'. x == y ? a[i++] : b[i++] @@ -5832,7 +5858,7 @@ that contain both `2400' and `foo'. -| fooey 555-1234 2400/1200/300 B The following command prints all records in `BBS-list' that contain -*either* `2400' or `foo', or both. +_either_ `2400' or `foo', or both. $ awk '/2400/ || /foo/' BBS-list -| alpo-net 555-3412 2400/1200/300 A @@ -5843,7 +5869,7 @@ that contain both `2400' and `foo'. -| sdace 555-3430 2400/1200/300 A -| sabafoo 555-2127 1200/300 C - The following command prints all records in `BBS-list' that do *not* + The following command prints all records in `BBS-list' that do _not_ contain the string `foo'. $ awk '! /foo/' BBS-list @@ -5964,7 +5990,7 @@ been read. For example: that contain the string `foo'. The `BEGIN' rule prints a title for the report. There is no need to use the `BEGIN' rule to initialize the counter `n' to zero, as `awk' does this automatically (*note -Variables::.). +Variables::). The second rule increments the variable `n' every time a record containing the pattern `foo' is read. The `END' rule prints the value @@ -6026,7 +6052,7 @@ it. The second point is similar to the first, but from the other direction. Inside an `END' rule, what is the value of `$0' and `NF'? Traditionally, due largely to implementation issues, `$0' and `NF' were -*undefined* inside an `END' rule. The POSIX standard specified that +_undefined_ inside an `END' rule. The POSIX standard specified that `NF' was available in an `END' rule, containing the number of fields from the last input record. Due most probably to an oversight, the standard does not say that `$0' is also preserved, although logically @@ -6050,7 +6076,7 @@ File: gawk.info, Node: Empty, Prev: BEGIN/END, Up: Pattern Overview The Empty Pattern ----------------- - An empty (i.e. non-existent) pattern is considered to match *every* + An empty (i.e. non-existent) pattern is considered to match _every_ input record. For example, the program: awk '{ print $1 }' BBS-list @@ -6093,7 +6119,7 @@ well. An omitted action is equivalent to `{ print $0 }'. Here are the kinds of statements supported in `awk': * Expressions, which can call functions or assign values to variables - (*note Expressions::.). Executing this kind of statement simply + (*note Expressions::). Executing this kind of statement simply computes the value of the expression. This is useful when the expression has side effects (*note Assignment Expressions: Assignment Ops.). @@ -6720,7 +6746,7 @@ specific to `gawk' are marked with an asterisk, `*'. the `gensub', `gsub', `index', `match', `split' and `sub' functions, record termination with `RS', and field splitting with `FS' all ignore case when doing their particular regexp operations. - The value of `IGNORECASE' does *not* affect array subscripting. + The value of `IGNORECASE' does _not_ affect array subscripting. *Note Case-sensitivity in Matching: Case-sensitivity. If `gawk' is in compatibility mode (*note Command Line Options: @@ -6738,7 +6764,7 @@ specific to `gawk' are marked with an asterisk, `*'. general expressions; this is now done by `CONVFMT'. `OFS' - This is the output field separator (*note Output Separators::.). + This is the output field separator (*note Output Separators::). It is output between the fields output by a `print' statement. Its default value is `" "', a string consisting of a single space. @@ -6947,7 +6973,7 @@ In this example, `ARGV[0]' contains `"awk"', `ARGV[1]' contains special command line options, with their arguments, are also not entered. This includes variable assignments done with the `-v' option (*note Command Line Options: Options.). Normal variable assignments on -the command line *are* treated as arguments, and do show up in the +the command line _are_ treated as arguments, and do show up in the `ARGV' array. $ cat showargs.awk @@ -7056,6 +7082,7 @@ array with the same name in the same `awk' program. * Multi-dimensional:: Emulating multi-dimensional arrays in `awk'. * Multi-scanning:: Scanning multi-dimensional arrays. +* Array Efficiency:: Implementation-specific tips. File: gawk.info, Node: Array Intro, Next: Reference to Elements, Prev: Arrays, Up: Arrays @@ -7193,9 +7220,9 @@ index `2', you could write this statement: if (2 in frequencies) print "Subscript 2 is present." - Note that this is *not* a test of whether or not the array -`frequencies' contains an element whose *value* is two. (There is no -way to do that except to scan all the elements.) Also, this *does not* + Note that this is _not_ a test of whether or not the array +`frequencies' contains an element whose _value_ is two. (There is no +way to do that except to scan all the elements.) Also, this _does not_ create `frequencies[2]', while the following (incorrect) alternative would do so: @@ -7365,7 +7392,7 @@ the presence of that element will return zero (i.e. false): if (4 in foo) print "This will never be printed" - It is important to note that deleting an element is *not* the same + It is important to note that deleting an element is _not_ the same as assigning it a null value (the empty string, `""'). foo[4] = "" @@ -7410,8 +7437,8 @@ File: gawk.info, Node: Numeric Array Subscripts, Next: Uninitialized Subscript Using Numbers to Subscript Arrays ================================= - An important aspect of arrays to remember is that *array subscripts -are always strings*. If you use a numeric value as a subscript, it + An important aspect of arrays to remember is that _array subscripts +are always strings_. If you use a numeric value as a subscript, it will be converted to a string value before it is used for subscripting (*note Conversion of Strings and Numbers: Conversion.). @@ -7476,7 +7503,7 @@ the output! At first glance, this program should have worked. The variable `lines' is uninitialized, and uninitialized variables have the numeric -value zero. So, the value of `l[0]' should have been printed. +value zero. So, `awk' should have printed the value of `l[0]'. The issue here is that subscripts for `awk' arrays are *always* strings. And uninitialized variables, when used as strings, have the @@ -7585,7 +7612,7 @@ it produces: 3 2 1 6 -File: gawk.info, Node: Multi-scanning, Prev: Multi-dimensional, Up: Arrays +File: gawk.info, Node: Multi-scanning, Next: Array Efficiency, Prev: Multi-dimensional, Up: Arrays Scanning Multi-dimensional Arrays ================================= @@ -7593,7 +7620,7 @@ Scanning Multi-dimensional Arrays There is no special `for' statement for scanning a "multi-dimensional" array; there cannot be one, because in truth there are no multi-dimensional arrays or elements; there is only a -multi-dimensional *way of accessing* an array. +multi-dimensional _way of accessing_ an array. However, if your program has an array that is always accessed as multi-dimensional, you can get the effect of scanning it by combining @@ -7626,6 +7653,34 @@ to `"foo"'. Presto, the original sequence of separate indices has been recovered. +File: gawk.info, Node: Array Efficiency, Prev: Multi-scanning, Up: Arrays + +Using Array Memory Efficiently +============================== + + This section applies just to `gawk'. + + It is often useful to use the same bit of data as an index into +multiple arrays. Due to the way `gawk' implements associative arrays, +when you need to use input data as an index for multiple arrays, it is +much more effecient to assign the input field to a separate variable, +and then use that variable as the index. + + { + name = $1 + ssn = $2 + nkids = $3 + ... + seniority[name]++ # better than seniority[$1]++ + kids[name] = nkids # better than kids[$1] = nkids + } + + Using separate variables with mnemonic names for the input fields +makes programs more readable, in any case. It is an eventual goal to +make `gawk''s array indexing as efficient as possible, no matter what +the source of the index value. + + File: gawk.info, Node: Built-in, Next: User-defined, Prev: Arrays, Up: Top Built-in Functions @@ -7745,9 +7800,9 @@ Optional parameters are enclosed in square brackets ("[" and "]"). return int(n * rand()) } - The multiplication produces a random real number greater than zero - and less than `n'. We then make it an integer (using `int') - between zero and `n' - 1, inclusive. + The multiplication produces a random number greater than zero and + less than `n'. We then make it an integer (using `int') between + zero and `n' - 1, inclusive. Here is an example where a similar function is used to produce random integers between one and N. This program prints a new @@ -7968,10 +8023,10 @@ and "]"). awk 'BEGIN { str = "daabaaa" - sub(/a*/, "c&c", str) + sub(/a+/, "C&C", str) print str }' - -| dcaacbaaa + -| dCaaCbaaa This shows how `&' can represent a non-constant string, and also illustrates the "leftmost, longest" rule in regexp matching (*note @@ -8007,7 +8062,7 @@ and "]"). `gsub(REGEXP, REPLACEMENT [, TARGET])' This is similar to the `sub' function, except `gsub' replaces - *all* of the longest, leftmost, *non-overlapping* matching + _all_ of the longest, leftmost, _non-overlapping_ matching substrings it can find. The `g' in `gsub' stands for "global," which means replace everywhere. For example: @@ -8028,7 +8083,7 @@ and "]"). `gsub', it searches the target string TARGET for matches of the regular expression REGEXP. Unlike `sub' and `gsub', the modified string is returned as the result of the function, and the original - target string is *not* changed. If HOW is a string beginning with + target string is _not_ changed. If HOW is a string beginning with `g' or `G', then it replaces all matches of REGEXP with REPLACEMENT. Otherwise, HOW is a number indicating which match of REGEXP to replace. If no TARGET is supplied, `$0' is used instead. @@ -8087,7 +8142,7 @@ and "]"). also returned if LENGTH is greater than the number of characters remaining in the string, counting from character number START. - *Note:* The string returned by `substr' *cannot* be assigned to. + *Note:* The string returned by `substr' _cannot_ be assigned to. Thus, it is a mistake to attempt to change a portion of a string, like this: @@ -8183,7 +8238,7 @@ leads to two problems. 1. Backslashes must now be doubled in the REPLACEMENT string, breaking historical `awk' programs. - 2. To make sure that an `awk' program is portable, *every* character + 2. To make sure that an `awk' program is portable, _every_ character in the REPLACEMENT string must be preceded with a backslash.(1) The POSIX standard is under revision.(2) Because of the above @@ -8235,8 +8290,8 @@ the use of `gawk' and `gensub' for when you have to do substitutions. (1) This consequence was certainly unintended. - (2) As of April, 1999, with final approval and publication hopefully -sometime in 1997. + (2) As of June, 2000, with final approval and publication as part of +the Austin Group Standards hopefully sometime in 2001. File: gawk.info, Node: I/O Functions, Next: Time Functions, Prev: String Functions, Up: Built-in @@ -8278,7 +8333,7 @@ parameters are enclosed in square brackets ("[" and "]"). `gawk' extends the `fflush' function in two ways. The first is to allow no argument at all. In this case, the buffer for the standard output is flushed. The second way is to allow the null - string (`""') as the argument. In this case, the buffers for *all* + string (`""') as the argument. In this case, the buffers for _all_ open output files and pipes are flushed. `fflush' returns zero if the buffer was successfully flushed, and @@ -8671,7 +8726,7 @@ User-defined Functions Complicated `awk' programs can often be simplified by defining your own functions. User-defined functions can be called just like built-in -ones (*note Function Calls::.), but it is up to you to define them--to +ones (*note Function Calls::), but it is up to you to define them--to tell `awk' what they should do. * Menu: @@ -8690,7 +8745,7 @@ Function Definition Syntax 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. +to include sequences of rules _and_ user-defined function definitions. There is no need in `awk' to put the definition of a function before all uses of the function. This is because `awk' reads the entire program before starting to execute any of it. @@ -8715,7 +8770,7 @@ cannot have two parameters with the same name. The BODY-OF-FUNCTION consists of `awk' statements. It is the most important part of the definition, because it says what the function -should actually *do*. The argument names exist to give the body a way +should actually _do_. The argument names exist to give the body a way to talk about the arguments; local variables, to give the body places to keep temporary values. @@ -8756,7 +8811,7 @@ function. When this happens, we say the function is "recursive". `function' may be abbreviated `func'. However, POSIX only specifies the use of the keyword `function'. This actually has some practical implications. If `gawk' is in POSIX-compatibility mode (*note Command -Line Options: Options.), then the following statement will *not* define +Line Options: Options.), then the following statement will _not_ define a function: func foo() { a = sqrt($1) ; print a } @@ -8813,7 +8868,9 @@ this program, using our function to format the results, prints: elements in an array and start over with a new list of elements (*note The `delete' Statement: Delete.). Instead of having to repeat this loop everywhere in your program that you need to clear out an array, -your program can just call `delarray'. +your program can just call `delarray'. (This guarantees portability. +The usage `delete ARRAY' to delete the contents of an entire array is a +non-standard extension.) Here is an example of a recursive function. It takes a string as an input parameter, and returns the string in backwards order. @@ -8877,7 +8934,7 @@ concatenate a variable with an expression in parentheses. However, it notices that you used a function name and not a variable name, and reports an error. - When a function is called, it is given a *copy* of the values of its + When a function is called, it is given a _copy_ of the values of its arguments. This is known as "call by value". The caller may use a variable as the expression for the argument, but the called function does not know this: it only knows what value the argument had. For @@ -8900,18 +8957,18 @@ this has no effect on any other variables. Thus, if `myfunc' does this: print str } -to change its first argument variable `str', this *does not* change the +to change its first argument variable `str', this _does not_ change the value of `foo' in the caller. The role of `foo' in calling `myfunc' ended when its value, `"bar"', was computed. If `str' also exists outside of `myfunc', the function body cannot alter this outer value, because it is shadowed during the execution of `myfunc' and cannot be seen or changed from there. - However, when arrays are the parameters to functions, they are *not* + However, when arrays are the parameters to functions, they are _not_ copied. Instead, the array itself is made available for direct manipulation by the function. This is usually called "call by reference". Changes made to an array parameter inside the body of a -function *are* visible outside that function. This can be *very* +function _are_ visible outside that function. This can be *very* dangerous if you do not watch what you are doing. For example: function changeit(array, ind, nvalue) @@ -8972,7 +9029,7 @@ value is undefined and, therefore, unpredictable. A `return' statement with no value expression is assumed at the end of every function definition. So if control reaches the end of the function body, then the function returns an unpredictable value. `awk' -will *not* warn you if you use the return value of such a function. +will _not_ warn you if you use the return value of such a function. Sometimes, you want to write a function for what it does, not for what it returns. Such a function corresponds to a `void' function in C @@ -9108,6 +9165,11 @@ The options and their meanings are as follows: than once, setting another variable each time, like this: `awk -v foo=1 -v bar=2 ...'. + *Caution:* Using `-v' to set the values of the builtin variables + may lead to suprising results. `awk' will reset the values of + those variables as it needs to, possibly ignoring any predefined + value you may have given. + `-mf NNN' `-mr NNN' Set various memory limits to the value NNN. The `f' flag sets the @@ -9179,7 +9241,7 @@ The options and their meanings are as follows: restrictions: * `\x' escape sequences are not recognized (*note Escape - Sequences::.). + Sequences::). * Newlines do not act as whitespace to separate fields when `FS' is equal to a single space. @@ -9297,7 +9359,7 @@ argument that has the form `VAR=VALUE', assigns the value VALUE to the variable VAR--it does not specify a file at all. All these arguments are made available to your `awk' program in the -`ARGV' array (*note Built-in Variables::.). Command line options and +`ARGV' array (*note Built-in Variables::). Command line options and the program text (if present) are omitted from `ARGV'. All other arguments, including variable assignments, are included. As each element of `ARGV' is processed, `gawk' sets the variable `ARGIND' to @@ -9311,15 +9373,15 @@ reading a file. Therefore, the variables actually receive the given values after all previously specified files have been read. In particular, the values of -variables assigned in this fashion are *not* available inside a `BEGIN' +variables assigned in this fashion are _not_ available inside a `BEGIN' rule (*note The `BEGIN' and `END' Special Patterns: BEGIN/END.), since such rules are run before `awk' begins scanning the argument list. The variable values given on the command line are processed for -escape sequences (d.c.) (*note Escape Sequences::.). +escape sequences (d.c.) (*note Escape Sequences::). In some earlier implementations of `awk', when a variable assignment -occurred before any file names, the assignment would happen *before* +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. However, some applications came to depend upon @@ -9392,11 +9454,10 @@ path `gawk' will use. ---------- Footnotes ---------- - (1) Your version of `gawk' may use a directory that is different -than `/usr/local/share/awk'; it will depend upon how `gawk' was built -and installed. The actual directory will be the value of `$(datadir)' -generated when `gawk' was configured. You probably don't need to worry -about this though. + (1) Your version of `gawk' may use a different directory; it will +depend upon how `gawk' was built and installed. The actual directory +will be the value of `$(datadir)' generated when `gawk' was configured. +You probably don't need to worry about this though. File: gawk.info, Node: Obsolete, Next: Undocumented, Prev: AWKPATH Variable, Up: Invoking Gawk @@ -9407,9 +9468,9 @@ Obsolete Options and/or Features This section describes features and/or command line options from previous releases of `gawk' that are either not available in the current version, or that are still supported but deprecated (meaning -that they will *not* be in the next release). +that they will _not_ be in the next release). - For version 3.0.4 of `gawk', there are no command line options or + For version 3.0.5 of `gawk', there are no command line options or other deprecated features from the previous version of `gawk'. This node is thus essentially a place holder, in case some option becomes obsolete in a future version of `gawk'. @@ -9423,6 +9484,8 @@ Undocumented Options and Features Use the Source, Luke! Obi-Wan + + This section intentionally left blank. @@ -9570,7 +9633,7 @@ file is reached, and a new data file is opened, changing the value of and then executes a `next' statement to start the loop going.(1) This initial version has a subtle problem. What happens if the same -data file is listed *twice* on the command line, one right after the +data file is listed _twice_ on the command line, one right after the other, or even with just a variable assignment between the two occurrences of the file name? @@ -9945,7 +10008,8 @@ canonical representation of a date into a timestamp. It would appear at first glance that `gawk' would have to supply a `mktime' built-in function that was simply a "hook" to the C language -version. In fact though, `mktime' can be implemented entirely in `awk'. +version. In fact though, `mktime' can be implemented entirely in +`awk'.(1) Here is a version of `mktime' for `awk'. It takes a simple representation of the date and time, and converts it into a timestamp. @@ -10055,7 +10119,7 @@ efficient. } The function starts with a first approximation of all the seconds -between Midnight, January 1, 1970,(1) and the beginning of the current +between Midnight, January 1, 1970,(2) and the beginning of the current year. It then goes through all those years, and for every leap year, adds an additional day's worth of seconds. @@ -10130,7 +10194,7 @@ set-up and error checking. Recall that `_tm_addup' generated a value in seconds since Midnight, January 1, 1970. This value is not directly usable as the result we -want, *since the calculation does not account for the local timezone*. +want, _since the calculation does not account for the local timezone_. In other words, the value represents the count in seconds since the Epoch, but only for UTC (Universal Coordinated Time). If the local timezone is east or west of UTC, then some number of hours should be @@ -10146,8 +10210,8 @@ the result. How can `mktime' determine how far away it is from UTC? This is surprisingly easy. The returned timestamp represents the time passed to -`mktime' *as UTC*. This timestamp can be fed back to `strftime', which -will format it as a *local* time; i.e. as if it already had the UTC +`mktime' _as UTC_. This timestamp can be fed back to `strftime', which +will format it as a _local_ time; i.e. as if it already had the UTC difference added in to it. This is done by giving `"%Y %m %d %H %M %S"' to `strftime' as the format argument. It returns the computed timestamp in the original string format. The result @@ -10163,7 +10227,6 @@ An example demonstrating this is presented below. if (_tm_test) { printf "Enter date as yyyy mm dd hh mm ss: " getline _tm_test_date - t = mktime(_tm_test_date) r = strftime("%Y %m %d %H %M %S", t) printf "Got back (%s)\n", r @@ -10199,7 +10262,11 @@ months, and AM/PM times into 24-hour clocks, to generate the ---------- Footnotes ---------- - (1) This is the Epoch on POSIX systems. It may be different on + (1) June, 2000: Actually, I was mistaken when I wrote this. The +version presented here doesn't always work correctly, and the next +major version of `gawk' will provide `mktime' as a built-in function. + + (2) This is the Epoch on POSIX systems. It may be different on other systems. @@ -10310,7 +10377,7 @@ even supplied us the code to do so. library program. It arranges to call two user-supplied functions, `beginfile' and `endfile', at the beginning and end of each data file. Besides solving the problem in only nine(!) lines of code, it does so -*portably*; this will work with any implementation of `awk'. +_portably_; this will work with any implementation of `awk'. # transfile.awk # @@ -11205,7 +11272,7 @@ that it is global, while the fact that the variable name is not all capital letters indicates that the variable is not one of `awk''s built-in variables, like `FS'. - It is also important that *all* variables in library functions that + It is also important that _all_ variables in library functions that do not need to save state are in fact declared local. If this is not done, the variable could accidentally be used in the user's program, leading to bugs that are very difficult to track down. @@ -11568,7 +11635,7 @@ is preceded by the name of the file and a colon. `-v' Invert the sense of the test. `egrep' prints the lines that do - *not* match the pattern, and exits successfully if the pattern was + _not_ match the pattern, and exits successfully if the pattern was not matched. `-i' @@ -11590,7 +11657,7 @@ Function.). The program begins with a descriptive comment, and then a `BEGIN' rule that processes the command line arguments with `getopt'. The `-i' (ignore case) option is particularly easy with `gawk'; we just use the -`IGNORECASE' built in variable (*note Built-in Variables::.). +`IGNORECASE' built in variable (*note Built-in Variables::). # egrep.awk --- simulate egrep in awk # Arnold Robbins, arnold@gnu.org, Public Domain @@ -12139,7 +12206,7 @@ standard output, `/dev/stdout'. # -n skip n fields # +n skip n characters, skip fields first - BEGIN \ + BEGIN \ { count = 1 outputfile = "/dev/stdout" @@ -12367,8 +12434,7 @@ 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. - function beginfile(file) - { + function beginfile(file) { chars = lines = words = 0 fname = FILENAME } @@ -12735,7 +12801,7 @@ the lists be enclosed in square brackets and quoted. This is a feature. (2) This program was written before `gawk' acquired the ability to split each character in a string into separate array elements. How -might this ability simplify the program? +might you use this new feature to simplify the program? File: gawk.info, Node: Labels Program, Next: Word Sorting, Prev: Translate Program, Up: Miscellaneous Programs @@ -12873,7 +12939,7 @@ program listing. rules. The first rule, because it has an empty pattern, is executed on every line of the input. It uses `awk''s field-accessing mechanism (*note Examining Fields: Fields.) to pick out the individual words from -the line, and the built-in variable `NF' (*note Built-in Variables::.) +the line, and the built-in variable `NF' (*note Built-in Variables::) to know how many fields are available. For each input word, an element of the array `freq' is incremented to @@ -12961,7 +13027,7 @@ Removing Duplicates from Unsorted Text -------------------------------------- The `uniq' program (*note Printing Non-duplicated Lines of Text: -Uniq Program.), removes duplicate lines from *sorted* data. +Uniq Program.), removes duplicate lines from _sorted_ data. Suppose, however, you need to remove duplicate lines from a data file, but that you wish to preserve the order the lines are in? A good @@ -13085,8 +13151,7 @@ exited with a zero exit status, signifying OK. # extract.awk --- extract files and run programs # from texinfo files - # Arnold Robbins, arnold@gnu.org, Public Domain - # May 1993 + # Arnold Robbins, arnold@gnu.org, Public Domain, May 1993 BEGIN { IGNORECASE = 1 } @@ -13398,7 +13463,6 @@ are several cases of interest. The source text is echoed into `/tmp/ig.s.$$'. `--version' -`--version' `-Wversion' `igawk' prints its version number, and runs `gawk --version' to get the `gawk' version information, and then exits. @@ -13713,7 +13777,7 @@ changes, with cross-references to further details. Functions for Input/Output: I/O Functions.). * The `ARGC', `ARGV', `FNR', `RLENGTH', `RSTART', and `SUBSEP' - built-in variables (*note Built-in Variables::.). + built-in variables (*note Built-in Variables::). * The conditional expression using the ternary operator `?:' (*note Conditional Expressions: Conditional Exp.). @@ -13735,7 +13799,7 @@ changes, with cross-references to further details. How to Use Regular Expressions: Regexp Usage.). * The escape sequences `\b', `\f', and `\r' (*note Escape - Sequences::.). (Some vendors have updated their old versions of + Sequences::). (Some vendors have updated their old versions of `awk' to recognize `\r', `\b', and `\f', but this is not something you can rely on.) @@ -13757,7 +13821,7 @@ Changes between SVR3.1 and SVR4 The System V Release 4 version of Unix `awk' added these features (some of which originated in `gawk'): - * The `ENVIRON' variable (*note Built-in Variables::.). + * The `ENVIRON' variable (*note Built-in Variables::). * Multiple `-f' options on the command line (*note Command Line Options: Options.). @@ -13768,7 +13832,7 @@ Changes between SVR3.1 and SVR4 * The `--' option for terminating command line options. * The `\a', `\v', and `\x' escape sequences (*note Escape - Sequences::.). + Sequences::). * A defined return value for the `srand' built-in function (*note Numeric Built-in Functions: Numeric Functions.). @@ -13814,7 +13878,7 @@ introduced the following changes into the language: standard: * `\x' escape sequences are not recognized (*note Escape - Sequences::.). + Sequences::). * Newlines do not act as whitespace to separate fields when `FS' is equal to a single space. @@ -13852,6 +13916,7 @@ describes extensions in his version of `awk' that are not in POSIX * The `fflush' built-in function for flushing buffered output (*note Built-in Functions for Input/Output: I/O Functions.). + File: gawk.info, Node: POSIX/GNU, Prev: BTL, Up: Language History @@ -13902,11 +13967,11 @@ all be disabled with either the `--traditional' or `--posix' options Version 2.15 of `gawk' introduced these features: * The `ARGIND' variable, that tracks the movement of `FILENAME' - through `ARGV' (*note Built-in Variables::.). + through `ARGV' (*note Built-in Variables::). * The `ERRNO' variable, that contains the system error message when `getline' returns -1, or when `close' fails (*note Built-in - Variables::.). + Variables::). * The ability to use GNU-style long named options that start with `--' (*note Command Line Options: Options.). @@ -13967,6 +14032,7 @@ all be disabled with either the `--traditional' or `--posix' options * Amiga support (*note Installing `gawk' on an Amiga: Amiga Installation.). + File: gawk.info, Node: Gawk Summary, Next: Installation, Prev: Language History, Up: Top @@ -13986,7 +14052,7 @@ It is therefore terse, but complete. parts. * Actions Summary:: Quick overview of actions. * Functions Summary:: Defining and calling functions. -* Historical Features:: Some undocumented but supported "features". +* Historical Features:: Some undocumented but supported ``features''. File: gawk.info, Node: Command Line Summary, Next: Language Summary, Prev: Gawk Summary, Up: Gawk Summary @@ -14264,7 +14330,7 @@ Built-in Variables `!~', and the `gensub', `gsub', `index', `match', `split' and `sub' built-in functions all ignore case when doing regular expression operations, and all string comparisons are done - ignoring case. The value of `IGNORECASE' does *not* affect array + ignoring case. The value of `IGNORECASE' does _not_ affect array subscripting. `NF' @@ -14315,7 +14381,7 @@ Arrays ------ Arrays are subscripted with an expression between square brackets -(`[' and `]'). Array subscripts are *always* strings; numbers are +(`[' and `]'). Array subscripts are _always_ strings; numbers are converted to strings as necessary, following the standard conversion rules (*note Conversion of Strings and Numbers: Conversion.). @@ -14485,7 +14551,7 @@ Regular Expressions Regular expressions are based on POSIX EREs (extended regular expressions). The escape sequences allowed in string constants are -also valid in regular expressions (*note Escape Sequences::.). Regexps +also valid in regular expressions (*note Escape Sequences::). Regexps are composed of characters as follows: `C' @@ -14496,7 +14562,7 @@ are composed of characters as follows: matches the literal character C. `.' - matches any character, *including* newline. In strict POSIX mode, + matches any character, _including_ newline. In strict POSIX mode, `.' does not match the NUL character, which is a character with all bits equal to zero. @@ -14794,7 +14860,7 @@ I/O Statements `printf FMT, EXPR-LIST' Format and print. -`printf FMT, EXPR-LIST > file' +`printf FMT, EXPR-LIST > FILE' Format and print to FILE. If FILE does not exist, it is created. If it does exist, its contents are deleted the first time the `printf' is executed. @@ -14849,7 +14915,10 @@ following conversion specification formats: instead of `%e'. `%o' - An unsigned octal number (again, an integer). + An unsigned octal number (also an integer). + +`%u' + An unsigned decimal number (again, an integer). `%s' A character string. @@ -15291,7 +15360,8 @@ Getting the `gawk' Distribution Boston, MA 02111-1307 USA Phone: +1-617-542-5942 Fax (including Japan): +1-617-542-2652 - E-mail: `gnu@gnu.org' + Email: `gnu@gnu.org' + URL: `http://www.gnu.org/' Ordering from the FSF directly contributes to the support of the foundation and to the production of more free software. @@ -15382,21 +15452,21 @@ Extracting the Distribution `gawk' is distributed as a `tar' file compressed with the GNU Zip program, `gzip'. - Once you have the distribution (for example, `gawk-3.0.4.tar.gz'), + Once you have the distribution (for example, `gawk-3.0.5.tar.gz'), first 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 flags - gzip -d -c gawk-3.0.4.tar.gz | tar -xvpf - + gzip -d -c gawk-3.0.5.tar.gz | tar -xvpf - -This will create a directory named `gawk-3.0.4' in the current +This will create a directory named `gawk-3.0.5' in the current directory. The distribution file name is of the form `gawk-V.R.N.tar.gz'. The V represents the major version of `gawk', the R represents the current release of version V, and the N represents a "patch level", meaning that minor bugs have been fixed in the release. The current patch -level is 4, but when retrieving distributions, you should get the +level is 5, but when retrieving distributions, you should get the version with the highest version, release, and patch level. (Note that release levels greater than or equal to 90 denote "beta," or non-production software; you may not wish to retrieve such a version @@ -15569,7 +15639,7 @@ Compiling `gawk' for Unix ------------------------- After you have extracted the `gawk' distribution, `cd' to -`gawk-3.0.4'. Like most GNU software, `gawk' is configured +`gawk-3.0.5'. Like most GNU software, `gawk' is configured automatically for your Unix system by running the `configure' program. This program is a Bourne shell script that was generated automatically using GNU `autoconf'. (The `autoconf' software is described fully @@ -15755,7 +15825,7 @@ Running `gawk' on VMS Command line parsing and quoting conventions are significantly different on VMS, so examples in this Info file or from other sources -often need minor changes. They *are* minor though, and all `awk' +often need minor changes. They _are_ minor though, and all `awk' programs should run correctly. Here are a couple of trivial tests: @@ -15855,7 +15925,7 @@ MS-DOS and OS/2. The file `README_d/README.pc' in the `gawk' distribution contains additional notes, and `pc/Makefile' contains important notes on compilation options. - To build `gawk', copy the files in the `pc' directory (*except* for + To build `gawk', copy the files in the `pc' directory (_except_ for `ChangeLog') to the directory with the rest of the `gawk' sources. The `Makefile' contains a configuration section with comments, and may need to be edited in order to work with your `make' utility. @@ -15991,7 +16061,7 @@ function, which may not support this convention. Whenever it is possible that a file created by `gawk' will be used by some other program, use only backslashes. Also remember that in `awk', backslashes in strings have to be doubled in order to get literal -backslashes (*note Escape Sequences::.). +backslashes (*note Escape Sequences::). File: gawk.info, Node: Amiga Installation, Next: Bugs, Prev: Atari Installation, Up: Installation @@ -16036,6 +16106,8 @@ Reporting Problems and Bugs There is nothing more dangerous than a bored archeologist. The Hitchhiker's Guide to the Galaxy + + If you have problems with `gawk' or think that you have found a bug, please report it to the developers; we cannot promise to do anything but we might well want to fix it. @@ -16053,7 +16125,7 @@ idea of what kind of Unix system you're using, and the exact results `gawk' gave you. Also say what you expected to occur; this will help us decide whether the problem was really in the documentation. - Once you have a precise problem, there are two e-mail addresses you + Once you have a precise problem, there are two email addresses you can send mail to. Internet: @@ -16067,7 +16139,7 @@ get this information with the command `gawk --version'. You should send a carbon copy of your mail to Arnold Robbins, who can be reached at `arnold@gnu.org'. - *Important!* Do *not* try to report bugs in `gawk' by posting to the + *Important!* Do _not_ try to report bugs in `gawk' by posting to the Usenet/Internet newsgroup `comp.lang.awk'. While the `gawk' developers do occasionally read this newsgroup, there is no guarantee that we will see your posting. The steps described above are the official, @@ -16117,6 +16189,8 @@ Other Freely Available `awk' Implementations `// Do C++ comments work? answer: yes! of course' Michael Brennan + + There are two other freely available `awk' implementations. This section briefly describes where to get them. @@ -16129,8 +16203,8 @@ Unix `awk' This is a shell archive that has been compressed with the GNU `gzip' utility. It can be uncompressed with the `gunzip' utility. - You can also retrieve this version via the World Wide Web from - Brian Kernighan's home page (http://cm.bell-labs.com/who/bwk). + You can also retrieve this version via the World Wide Web from his + home page (http://cm.bell-labs.com/who/bwk). This version requires an ANSI C compiler; GCC (the GNU C compiler) works quite nicely. @@ -16228,7 +16302,7 @@ make it possible for me to include your changes. 2. See *note (Version)Top:: standards, GNU Coding Standards. This document describes how GNU software should be written. If you - haven't read it, please do so, preferably *before* starting to + haven't read it, please do so, preferably _before_ starting to modify `gawk'. (The `GNU Coding Standards' are available as part of the Autoconf distribution, from the FSF.) @@ -16293,7 +16367,7 @@ make it possible for me to include your changes. FSF to distribute your changes, you must either place those changes in the public domain, and submit a signed statement to that effect, or assign the copyright in your changes to the FSF. Both - of these actions are easy to do, and *many* people have done so + of these actions are easy to do, and _many_ people have done so already. If you have questions, please contact me (*note Reporting Problems and Bugs: Bugs.), or `gnu@gnu.org'. @@ -16322,6 +16396,10 @@ make it possible for me to include your changes. have to apply the changes manually, using a text editor, I may not do so, particularly if there are lots of changes. + 7. Include an entry for the `ChangeLog' file with your submission. + This further helps minimize the amount of work I have to do, + making it easier for me to accept patches. + 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, and if it isn't possible for me to do that with a minimum of extra work, @@ -16398,7 +16476,7 @@ several steps to follow. FSF to distribute your code, you must either place your code in the public domain, and submit a signed statement to that effect, or assign the copyright in your code to the FSF. Both of these - actions are easy to do, and *many* people have done so already. If + actions are easy to do, and _many_ people have done so already. If you have questions, please contact me, or `gnu@gnu.org'. Following these steps will make it much easier to integrate your @@ -16420,6 +16498,8 @@ Probable Future Extensions Hey! Larry Wall + + This section briefly lists extensions and possible improvements that indicate the directions we are currently considering for `gawk'. The file `FUTURES' in the `gawk' distributions lists these extensions as @@ -16441,7 +16521,7 @@ Databases A `PROCINFO' Array The special files that provide process-related information (*note - Special File Names in `gawk': Special Files.) may be superseded + Special File Names in `gawk': Special Files.) will be superseded by a `PROCINFO' array that would provide the same information, in an easier to access fashion. @@ -17233,7 +17313,7 @@ convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. ONE LINE TO GIVE THE PROGRAM'S NAME AND AN IDEA OF WHAT IT DOES. - Copyright (C) 19YY NAME OF AUTHOR + Copyright (C) YEAR NAME OF AUTHOR This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License @@ -17255,7 +17335,7 @@ mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: - Gnomovision version 69, Copyright (C) 19YY NAME OF AUTHOR + Gnomovision version 69, Copyright (C) YEAR NAME OF AUTHOR Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' @@ -18086,236 +18166,267 @@ Index Tag Table: -Node: Top1238 -Node: Preface20727 -Node: History22076 -Node: Manual History23434 -Node: Acknowledgements26876 -Node: What Is Awk30503 -Node: This Manual32157 -Node: Conventions34856 -Node: Sample Data Files36148 -Node: Getting Started39231 -Node: Names41539 -Node: Running gawk43108 -Node: One-shot44269 -Node: Read Terminal45656 -Node: Long47268 -Node: Executable Scripts48661 -Node: Comments51227 -Node: Very Simple53009 -Node: Two Rules55056 -Node: More Complex57235 -Node: Statements/Lines60351 -Node: Other Features64624 -Node: When65350 -Node: One-liners67285 -Node: Regexp70172 -Node: Regexp Usage71498 -Node: Escape Sequences73648 -Node: Regexp Operators79102 -Node: GNU Regexp Operators90135 -Node: Case-sensitivity93840 -Node: Leftmost Longest96956 -Node: Computed Regexps98491 -Node: Reading Files101148 -Node: Records102916 -Node: Fields109411 -Node: Non-Constant Fields112479 -Node: Changing Fields114766 -Node: Field Separators119174 -Node: Basic Field Splitting119876 -Node: Regexp Field Splitting123105 -Node: Single Character Fields125672 -Node: Command Line Field Separator126741 -Node: Field Splitting Summary129982 -Node: Constant Size132002 -Node: Multiple Line136039 -Node: Getline141447 -Node: Getline Intro142521 -Node: Plain Getline143484 -Node: Getline/Variable145748 -Node: Getline/File146890 -Node: Getline/Variable/File148200 -Node: Getline/Pipe150174 -Node: Getline/Variable/Pipe152382 -Node: Getline Summary153618 -Node: Printing155212 -Node: Print156280 -Node: Print Examples158381 -Node: Output Separators160989 -Node: OFMT162887 -Node: Printf164289 -Node: Basic Printf165193 -Node: Control Letters166727 -Node: Format Modifiers169415 -Node: Printf Examples173564 -Node: Redirection176343 -Node: Special Files180982 -Node: Close Files And Pipes186219 -Node: Expressions190280 -Node: Constants192476 -Node: Scalar Constants192955 -Node: Regexp Constants193959 -Node: Using Constant Regexps194421 -Node: Variables197622 -Node: Using Variables198276 -Node: Assignment Options199711 -Node: Conversion201656 -Node: Arithmetic Ops204838 -Node: Concatenation206972 -Node: Assignment Ops208394 -Node: Increment Ops213990 -Node: Truth Values216518 -Node: Typing and Comparison217566 -Node: Boolean Ops223573 -Node: Conditional Exp227266 -Node: Function Calls229043 -Node: Precedence231923 -Node: Patterns and Actions235311 -Node: Pattern Overview235737 -Node: Kinds of Patterns236512 -Node: Regexp Patterns237649 -Node: Expression Patterns238203 -Node: Ranges241855 -Node: BEGIN/END244579 -Node: Using BEGIN/END245048 -Node: I/O And BEGIN/END248011 -Node: Empty250027 -Node: Action Overview250326 -Node: Statements252898 -Node: If Statement254604 -Node: While Statement256107 -Node: Do Statement258138 -Node: For Statement259240 -Node: Break Statement262497 -Node: Continue Statement264768 -Node: Next Statement266764 -Node: Nextfile Statement269261 -Node: Exit Statement271175 -Node: Built-in Variables273186 -Node: User-modified274282 -Node: Auto-set279203 -Node: ARGC and ARGV285732 -Node: Arrays289571 -Node: Array Intro291034 -Node: Reference to Elements295074 -Node: Assigning Elements297024 -Node: Array Example297526 -Node: Scanning an Array299245 -Node: Delete301575 -Node: Numeric Array Subscripts303829 -Node: Uninitialized Subscripts305735 -Node: Multi-dimensional307379 -Node: Multi-scanning310474 -Node: Built-in312117 -Node: Calling Built-in313106 -Node: Numeric Functions315077 -Node: String Functions318895 -Node: I/O Functions338236 -Node: Time Functions344046 -Node: User-defined352896 -Node: Definition Syntax353609 -Node: Function Example357858 -Node: Function Caveats360188 -Node: Return Statement364059 -Node: Invoking Gawk366714 -Node: Options367949 -Node: Other Arguments376778 -Node: AWKPATH Variable379426 -Node: Obsolete382174 -Node: Undocumented382840 -Node: Known Bugs383089 -Node: Library Functions384227 -Node: Portability Notes386646 -Node: Nextfile Function387930 -Node: Assert Function392798 -Node: Round Function396150 -Node: Ordinal Functions397788 -Node: Join Function401232 -Node: Mktime Function403277 -Node: Gettimeofday Function414844 -Node: Filetrans Function418849 -Node: Getopt Function422512 -Node: Passwd Functions433861 -Node: Group Functions442182 -Node: Library Names450066 -Node: Sample Programs453991 -Node: Clones454482 -Node: Cut Program455576 -Node: Egrep Program465598 -Node: Id Program473254 -Node: Split Program476518 -Node: Tee Program479879 -Node: Uniq Program482668 -Node: Wc Program490206 -Node: Miscellaneous Programs494616 -Node: Dupword Program495526 -Node: Alarm Program497190 -Node: Translate Program501728 -Node: Labels Program506531 -Node: Word Sorting510067 -Node: History Sorting514412 -Node: Extract Program516374 -Node: Simple Sed523969 -Node: Igawk Program527306 -Node: Language History540619 -Node: V7/SVR3.1541852 -Node: SVR4544507 -Node: POSIX546029 -Node: BTL547649 -Node: POSIX/GNU548412 -Node: Gawk Summary552844 -Node: Command Line Summary553666 -Node: Language Summary556642 -Node: Variables/Fields559022 -Node: Fields Summary559756 -Node: Built-in Summary561542 -Node: Arrays Summary565257 -Node: Data Type Summary566550 -Node: Rules Summary568376 -Node: Pattern Summary569904 -Node: Regexp Summary572089 -Node: Actions Summary575472 -Node: Operator Summary577304 -Node: Control Flow Summary578531 -Node: I/O Summary579088 -Node: Printf Summary582077 -Node: Special File Summary585415 -Node: Built-in Functions Summary587093 -Node: Time Functions Summary591093 -Node: String Constants Summary591984 -Node: Functions Summary593304 -Node: Historical Features594365 -Node: Installation595863 -Node: Gawk Distribution597078 -Node: Getting597581 -Node: Extracting600532 -Node: Distribution contents601919 -Node: Unix Installation606695 -Node: Quick Installation607204 -Node: Configuration Philosophy608722 -Node: VMS Installation611124 -Node: VMS Compilation611663 -Node: VMS Installation Details613267 -Node: VMS Running614909 -Node: VMS POSIX616499 -Node: PC Installation617779 -Node: Atari Installation621182 -Node: Atari Compiling622366 -Node: Atari Using624275 -Node: Amiga Installation627122 -Node: Bugs628233 -Node: Other Versions631286 -Node: Notes632972 -Node: Compatibility Mode633579 -Node: Additions634422 -Node: Adding Code635120 -Node: New Ports640450 -Node: Future Extensions644610 -Node: Improvements646553 -Node: Glossary648421 -Node: Copying665492 -Node: Index684684 +Node: Top1206 +Node: Preface20764 +Ref: Preface-Footnote-121881 +Node: History22113 +Node: Manual History23471 +Node: Acknowledgements26913 +Node: What Is Awk30542 +Node: This Manual32196 +Node: Conventions34896 +Node: Sample Data Files36188 +Node: Getting Started39271 +Node: Names41579 +Ref: Names-Footnote-143076 +Node: Running gawk43148 +Node: One-shot44309 +Node: Read Terminal45696 +Node: Long47308 +Node: Executable 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