diff options
Diffstat (limited to 'doc/gawk.texi')
| -rw-r--r-- | doc/gawk.texi | 85 |
1 files changed, 53 insertions, 32 deletions
diff --git a/doc/gawk.texi b/doc/gawk.texi index 49229d19..a1f709cf 100644 --- a/doc/gawk.texi +++ b/doc/gawk.texi @@ -30033,21 +30033,19 @@ The following program (@file{values.awk}) illustrates this: @example @{ - $1 = $2 + $3 + sum = $1 + $2 # see it for what it is - printf("$1 = %.12g\n", $1) + printf("sum = %.12g\n", sum) # use CONVFMT - a = "<" $1 ">" + a = "<" sum ">" print "a =", a -@group # use OFMT - print "$1 =", $1 -@end group + print "sum =", sum @} @end example @noindent -This program shows the full value of the sum of @code{$2} and @code{$3} +This program shows the full value of the sum of @code{$1} and @code{$2} using @code{printf}, and then prints the string values obtained from both automatic conversion (via @code{CONVFMT}) and from printing (via @code{OFMT}). @@ -30055,10 +30053,10 @@ from printing (via @code{OFMT}). Here is what happens when the program is run: @example -$ @kbd{echo 2 3.654321 1.2345678 | awk -f values.awk} -@print{} $1 = 4.8888888 +$ @kbd{echo 3.654321 1.2345678 | awk -f values.awk} +@print{} sum = 4.8888888 @print{} a = <4.88889> -@print{} $1 = 4.88889 +@print{} sum = 4.88889 @end example This makes it clear that the full numeric value is different from @@ -30150,8 +30148,8 @@ source code constants.) @item Support for the special IEEE 754 floating point values ``Not A Number'' (NaN), positive Infinity (``inf'') and negative Infinity (``@minus{}inf''). -In particular, the format for these values is as specified by the ISO C99 -standard, which ignores case and can allow machine-dependent additional +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 @samp{nan} and allow either @samp{inf} or @samp{infinity}. @end itemize @@ -30190,9 +30188,9 @@ The solution implemented in @command{gawk} is as follows: With the @option{--posix} command-line option, @command{gawk} becomes ``hands off.'' String values are passed directly to the system library's @code{strtod()} function, and if it successfully returns a numeric value, -that is what's used. By definition, the results are not portable across -different systems.@footnote{You asked for it, you got it.} -They are also a little surprising: +that is what's used.@footnote{You asked for it, you got it.} +By definition, the results are not portable across +different systems. They are also a little surprising: @example $ @kbd{echo nanny | gawk --posix '@{ print $1 + 0 @}'} @@ -30250,6 +30248,13 @@ microcomputers. It is a good example of a program that would have been better written in another language. You can get it from @uref{http://awk.info/?awk100/aaa}. +@cindex Ada programming language +@cindex Programming languages, Ada +@item Ada +A programming language originally defined by the U.S.@: Department of +Defense for embedded programming. It was designed to enforce good +Software Engineering practices. + @cindex amazingly workable formatter (@command{awf}) @cindex @command{awf} (amazingly workable formatter) program @item Amazingly Workable Formatter (@command{awf}) @@ -30347,6 +30352,7 @@ numerical, I/O-related, and string computations. Examples are @code{sqrt()} (for the square root of a number) and @code{substr()} (for a substring of a string). @command{gawk} provides functions for timestamp management, bit manipulation, +array sorting, type checking, and runtime string translation. (@xref{Built-in}.) @@ -30399,8 +30405,7 @@ The system programming language that most GNU software is written in. The points out similarities between @command{awk} and C when appropriate. In general, @command{gawk} attempts to be as similar to the 1990 version -of ISO C as makes sense. Future versions of @command{gawk} may adopt features -from the newer 1999 standard, as appropriate. +of ISO C as makes sense. @item C++ A popular object-oriented programming language derived from C. @@ -30458,7 +30463,7 @@ expression is the value of @var{expr2}; otherwise the value is is evaluated. (@xref{Conditional Exp}.) @item Comparison Expression -A relation that is either true or false, such as @samp{(a < b)}. +A relation that is either true or false, such as @samp{a < b}. Comparison expressions are used in @code{if}, @code{while}, @code{do}, and @code{for} statements, and in patterns to select which input records to process. @@ -30496,7 +30501,7 @@ The situation in which two communicating processes are each waiting for the other to perform an action. @item Debugger -A program used to help developers remove ``bugs'' (de-bug) from +A program used to help developers remove ``bugs'' from (de-bug) their programs. @item Double Precision @@ -30569,8 +30574,8 @@ See also ``Double Precision'' and ``Single Precision.'' Format strings are used to control the appearance of output in the @code{strftime()} and @code{sprintf()} functions, and are used in the @code{printf} statement as well. Also, data conversions from numbers to strings -are controlled by the format string contained in the built-in variable -@code{CONVFMT}. (@xref{Control Letters}.) +are controlled by the format strings contained in the built-in variables +@code{CONVFMT} and @code{OFMT}. (@xref{Control Letters}.) @item Free Documentation License This document describes the terms under which this @value{DOCUMENT} @@ -30637,6 +30642,7 @@ Base 16 notation, where the digits are @code{0}--@code{9} and representing 10, @samp{B} representing 11, and so on, up to @samp{F} for 15. Hexadecimal numbers are written in C using a leading @samp{0x}, to indicate their base. Thus, @code{0x12} is 18 (1 times 16 plus 2). +@xref{Nondecimal-numbers}. @item I/O Abbreviation for ``Input/Output,'' the act of moving data into and/or @@ -30664,7 +30670,7 @@ See also ``Compiler.'' @item Interval Expression A component of a regular expression that lets you specify repeated matches of -some part of the regexp. Interval expressions were not traditionally available +some part of the regexp. Interval expressions were not originally available in @command{awk} programs. @cindex ISO @@ -30676,13 +30682,23 @@ In the computer arena, important standards like those for C, C++, and POSIX become both American national and ISO international standards simultaneously. This @value{DOCUMENT} refers to Standard C as ``ISO C'' throughout. +@cindex Java programming language +@cindex Programming languages, Java +@item Java +A modern programming language originally developed by Sun Microsystems +(now Oracle) supporting Object-Oriented programming. Although usually +implemented by compiling to the instructions for a standard virtual +machine (the JVM), the language can be compiled to native code. + @item Keyword In the @command{awk} language, a keyword is a word that has special meaning. Keywords are reserved and may not be used as variable names. @command{gawk}'s keywords are: @code{BEGIN}, +@code{BEGINFILE}, @code{END}, +@code{ENDFILE}, @code{break}, @code{case}, @code{continue}, @@ -30753,12 +30769,13 @@ occurrences of the field separator appear next to each other. @item Number A numeric-valued data object. Modern @command{awk} implementations use double precision floating-point to represent numbers. -Very old @command{awk} implementations use single precision floating-point. +Ancient @command{awk} implementations used single precision floating-point. @item Octal Base-eight notation, where the digits are @code{0}--@code{7}. Octal numbers are written in C using a leading @samp{0}, to indicate their base. Thus, @code{013} is 11 (one times 8 plus 3). +@xref{Nondecimal-numbers}. @cindex P1003.1 POSIX standard @cindex P1003.2 POSIX standard @@ -30781,6 +30798,8 @@ that specify a Portable Operating System interface. The ``IX'' denotes the Unix heritage of these standards. The main standard of interest for @command{awk} users is @cite{IEEE Standard for Information Technology, Standard 1003.1-2008}. +The 2008 POSIX standard can be found online at +@url{http://www.opengroup.org/onlinepubs/9699919799/}. @item Precedence The order in which operations are performed when operators are used @@ -30799,7 +30818,8 @@ specify single lines. (@xref{Pattern Overview}.) @item Recursion When a function calls itself, either directly or indirectly. -If this isn't clear, refer to the entry for ``recursion.'' +As long as this is not clear, refer to the entry for ``recursion.'' +If this is clear, stop, and proceed to the next entry. @item Redirection Redirection means performing input from something other than the standard input @@ -30814,15 +30834,15 @@ operators. and @ref{Redirection}.) @item Regexp -Short for @dfn{regular expression}. A regexp is a pattern that denotes a -set of strings, possibly an infinite set. For example, the regexp -@samp{R.*xp} matches any string starting with the letter @samp{R} -and ending with the letters @samp{xp}. In @command{awk}, regexps are -used in patterns and in conditional expressions. Regexps may contain -escape sequences. (@xref{Regexp}.) +See ``Regular Expression.'' @item Regular Expression -See ``regexp.'' +A regular expression (``regexp'' for short) is a pattern that denotes a +set of strings, possibly an infinite set. For example, the regular expression +@samp{R.*xp} matches any string starting with the letter @samp{R} +and ending with the letters @samp{xp}. In @command{awk}, regular expressions are +used in patterns and in conditional expressions. Regular expressions may contain +escape sequences. (@xref{Regexp}.) @item Regular Expression Constant A regular expression constant is a regular expression written within @@ -30930,7 +30950,8 @@ AT&T Bell Laboratories. It initially became popular in universities around the world and later moved into commercial environments as a software development system and network server system. There are many commercial versions of Unix, as well as several work-alike systems whose source code -is freely available (such as GNU/Linux, NetBSD, FreeBSD, and OpenBSD). +is freely available (such as GNU/Linux, @uref{http://www.netbsd.org, NetBSD}, +@uref{http://www.freebsd.org, FreeBSD}, and @uref{http://www.openbsd.org, OpenBSD}). @item UTC The accepted abbreviation for ``Universal Coordinated Time.'' |