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Diffstat (limited to 'doc/gawk.texi')
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diff --git a/doc/gawk.texi b/doc/gawk.texi index fa3e5871..2d23581c 100644 --- a/doc/gawk.texi +++ b/doc/gawk.texi @@ -120,13 +120,6 @@ @end macro @end ifnothtml -@set FN file name -@set FFN File Name -@set DF data file -@set DDF Data File -@set PVERSION version -@set CTL Ctrl - @ignore Some comments on the layout for TeX. 1. Use at least texinfo.tex 2000-09-06.09 @@ -1188,11 +1181,11 @@ wrote the bulk of @cite{TCP/IP Internetworking with @command{gawk}} (a separate document, available as part of the @command{gawk} distribution). His code finally became part of the main @command{gawk} distribution -with @command{gawk} @value{PVERSION} 3.1. +with @command{gawk} version 3.1. John Haque rewrote the @command{gawk} internals, in the process providing an @command{awk}-level debugger. This version became available as -@command{gawk} @value{PVERSION} 4.0, in 2011. +@command{gawk} version 4.0, in 2011. @xref{Contributors}, for a complete list of those who made important contributions to @command{gawk}. @@ -1446,13 +1439,13 @@ emphasized @emph{like this}, and if a point needs to be made strongly, it is done @strong{like this}. The first occurrence of a new term is usually its @dfn{definition} and appears in the same font as the previous occurrence of ``definition'' in this sentence. -Finally, @value{FN}s are indicated like this: @file{/path/to/ourfile}. +Finally, file names are indicated like this: @file{/path/to/ourfile}. @end ifnotinfo Characters that you type at the keyboard look @kbd{like this}. In particular, there are special characters called ``control characters.'' These are characters that you type by holding down both the @kbd{CONTROL} key and -another key, at the same time. For example, a @kbd{@value{CTL}-d} is typed +another key, at the same time. For example, a @kbd{Ctrl-d} is typed by first pressing and holding the @kbd{CONTROL} key, next pressing the @kbd{d} key and finally releasing both keys. @@ -1597,7 +1590,7 @@ of @cite{GAWK: The GNU Awk User's Guide}. Edition @value{EDITION} maintains the basic structure of Edition 1.0, but with significant additional material, reflecting the host of new features -in @command{gawk} @value{PVERSION} @value{VERSION}. +in @command{gawk} version @value{VERSION}. Of particular note is @ref{Array Sorting}, @ref{Bitwise Functions}, @@ -2033,9 +2026,9 @@ awk '@var{program}' @noindent @command{awk} applies the @var{program} to the @dfn{standard input}, which usually means whatever you type on the terminal. This continues -until you indicate end-of-file by typing @kbd{@value{CTL}-d}. +until you indicate end-of-file by typing @kbd{Ctrl-d}. (On other operating systems, the end-of-file character may be different. -For example, on OS/2, it is @kbd{@value{CTL}-z}.) +For example, on OS/2, it is @kbd{Ctrl-z}.) @cindex files, input, See input files @cindex input files, running @command{awk} without @@ -2081,7 +2074,7 @@ $ @kbd{awk '@{ print @}'} @print{} Four score and seven years ago, ... @kbd{What, me worry?} @print{} What, me worry? -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example @node Long @@ -2102,7 +2095,7 @@ awk -f @var{source-file} @var{input-file1} @var{input-file2} @dots{} @cindex command line, options @cindex options, command-line The @option{-f} instructs the @command{awk} utility to get the @command{awk} program -from the file @var{source-file}. Any @value{FN} can be used for +from the file @var{source-file}. Any file name can be used for @var{source-file}. For example, you could put the program: @example @@ -2127,8 +2120,8 @@ awk "BEGIN @{ print \"Don't Panic!\" @}" @noindent This was explained earlier (@pxref{Read Terminal}). -Note that you don't usually need single quotes around the @value{FN} that you -specify with @option{-f}, because most @value{FN}s don't contain any of the shell's +Note that you don't usually need single quotes around the file name that you +specify with @option{-f}, because most file names don't contain any of the shell's special characters. Notice that in @file{advice}, the @command{awk} program did not have single quotes around it. The quotes are only needed for programs that are provided on the @command{awk} command line. @@ -2138,7 +2131,7 @@ for programs that are provided on the @command{awk} command line. @c STARTOFRANGE qs2x @cindex @code{'} (single quote) If you want to clearly identify your @command{awk} program files as such, -you can add the extension @file{.awk} to the @value{FN}. This doesn't +you can add the extension @file{.awk} to the file name. This doesn't affect the execution of the @command{awk} program but it does make ``housekeeping'' easier. @@ -2165,13 +2158,13 @@ BEGIN @{ print "Don't Panic!" @} After making this file executable (with the @command{chmod} utility), simply type @samp{advice} at the shell and the system arranges to run @command{awk}@footnote{The -line beginning with @samp{#!} lists the full @value{FN} of an interpreter +line beginning with @samp{#!} lists the full file name of an interpreter to run and an optional initial command-line argument to pass to that interpreter. The operating system then runs the interpreter with the given argument and the full argument list of the executed program. The first argument -in the list is the full @value{FN} of the @command{awk} program. +in the list is the full file name of the @command{awk} program. The rest of the -argument list contains either options to @command{awk}, or @value{DF}s, +argument list contains either options to @command{awk}, or data files, or both. Note that on many systems @command{awk} may be found in @file{/usr/bin} instead of in @file{/bin}. Caveat Emptor.} as if you had typed @samp{awk -f advice}: @@ -2421,7 +2414,7 @@ awk -F"" '@var{program}' @var{files} # wrong! @noindent In the second case, @command{awk} will attempt to use the text of the program -as the value of @code{FS}, and the first @value{FN} as the text of the program! +as the value of @code{FS}, and the first file name as the text of the program! This results in syntax errors at best, and confusing behavior at worst. @end itemize @@ -2536,19 +2529,19 @@ gawk "@{ print \"\042\" $0 \"\042\" @}" @var{file} @node Sample Data Files -@section @value{DDF}s for the Examples +@section Data Files for the Examples @c For gawk >= 4.0, update these data files. No-one has such slow modems! @cindex input files, examples @cindex @code{BBS-list} file Many of the examples in this @value{DOCUMENT} take their input from two sample -@value{DF}s. The first, @file{BBS-list}, represents a list of +data files. The first, @file{BBS-list}, represents a list of computer bulletin board systems together with information about those systems. -The second @value{DF}, called @file{inventory-shipped}, contains +The second data file, called @file{inventory-shipped}, contains information about monthly shipments. In both files, each line is considered to be one @dfn{record}. -In the @value{DF} @file{BBS-list}, each record contains the name of a computer +In the data file @file{BBS-list}, each record contains the name of a computer bulletin board, its phone number, the board's baud rate(s), and a code for the number of hours it is operational. An @samp{A} in the last column means the board operates 24 hours a day. A @samp{B} in the last @@ -2578,7 +2571,7 @@ sabafoo 555-2127 1200/300 C @end example @cindex @code{inventory-shipped} file -The @value{DF} @file{inventory-shipped} represents +The data file @file{inventory-shipped} represents information about shipments during the year. Each record contains the month, the number of green crates shipped, the number of red boxes shipped, the number of @@ -2622,7 +2615,7 @@ learn in this @value{DOCUMENT}. @cindex Texinfo If you are using the stand-alone version of Info, see @ref{Extract Program}, -for an @command{awk} program that extracts these @value{DF}s from +for an @command{awk} program that extracts these data files from @file{gawk.texi}, the Texinfo source file for this Info file. @end ifinfo @@ -2685,9 +2678,9 @@ collection of useful, short programs to get you started. Some of these programs contain constructs that haven't been covered yet. (The description of the program will give you a good idea of what is going on, but please read the rest of the @value{DOCUMENT} to become an @command{awk} expert!) -Most of the examples use a @value{DF} named @file{data}. This is just a +Most of the examples use a data file named @file{data}. This is just a placeholder; if you use these programs yourself, substitute -your own @value{FN}s for @file{data}. +your own file names for @file{data}. For future reference, note that there is often more than one way to do things in @command{awk}. At some point, you may want to look back at these examples and see if @@ -2777,7 +2770,7 @@ awk 'END @{ print NR @}' data @end example @item -Print the even-numbered lines in the @value{DF}: +Print the even-numbered lines in the data file: @example awk 'NR % 2 == 0' data @@ -2819,7 +2812,7 @@ This program prints every line that contains the string @samp{12} @emph{or} the string @samp{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 @value{DF}s, +This is what happens if we run this program on our two sample data files, @file{BBS-list} and @file{inventory-shipped}: @example @@ -2885,7 +2878,7 @@ the file. The fourth field identifies the group of the file. The fifth field contains the size of the file in bytes. The sixth, seventh, and eighth fields contain the month, day, and time, respectively, that the file was last modified. Finally, the ninth field -contains the @value{FN}.@footnote{The @samp{LC_ALL=C} is +contains the file name.@footnote{The @samp{LC_ALL=C} is needed to produce this traditional-style output from @command{ls}.} @c @cindex automatic initialization @@ -3294,8 +3287,8 @@ conventions. @cindex @code{-} (hyphen), filenames beginning with @cindex hyphen (@code{-}), filenames beginning with -This is useful if you have @value{FN}s that start with @samp{-}, -or in shell scripts, if you have @value{FN}s that will be specified +This is useful if you have file names that start with @samp{-}, +or in shell scripts, if you have file names that will be specified by the user that could start with @samp{-}. It is also useful for passing options on to the @command{awk} program; see @ref{Getopt Function}. @@ -3513,7 +3506,7 @@ when parsing numeric input data (@pxref{Locales}). Enable pretty-printing of @command{awk} programs. By default, output program is created in a file named @file{awkprof.out}. The optional @var{file} argument allows you to specify a different -@value{FN} for the output. +file name for the output. No space is allowed between the @option{-o} and @var{file}, if @var{file} is supplied. @@ -3534,7 +3527,7 @@ Enable profiling of @command{awk} programs (@pxref{Profiling}). By default, profiles are created in a file named @file{awkprof.out}. The optional @var{file} argument allows you to specify a different -@value{FN} for the profile file. +file name for the profile file. No space is allowed between the @option{-p} and @var{file}, if @var{file} is supplied. @@ -3662,7 +3655,7 @@ function names must be unique.) With standard @command{awk}, library functions can still be used, even if the program is entered at the terminal, by specifying @samp{-f /dev/tty}. After typing your program, -type @kbd{@value{CTL}-d} (the end-of-file character) to terminate it. +type @kbd{Ctrl-d} (the end-of-file character) to terminate it. (You may also use @samp{-f -} to read program source from the standard input but then you will not be able to also use the standard input as a source of data.) @@ -3744,9 +3737,9 @@ sets the variable @code{ARGIND} to the index in @code{ARGV} of the current element. @cindex input files, variable assignments and -The distinction between @value{FN} arguments and variable-assignment +The distinction between file name arguments and variable-assignment arguments is made when @command{awk} is about to open the next input file. -At that point in execution, it checks the @value{FN} to see whether +At that point in execution, it checks the file name to see whether it is really a variable assignment; if so, @command{awk} sets the variable instead of reading a file. @@ -3763,7 +3756,7 @@ sequences (@pxref{Escape Sequences}). @value{DARKCORNER} In some earlier implementations of @command{awk}, when a variable assignment -occurred before any @value{FN}s, the assignment would happen @emph{before} +occurred before any file names, the assignment would happen @emph{before} the @code{BEGIN} rule was executed. @command{awk}'s behavior was thus inconsistent; some command-line assignments were available inside the @code{BEGIN} rule, while others were not. Unfortunately, @@ -3774,8 +3767,8 @@ upon the old behavior. The variable assignment feature is most useful for assigning to variables such as @code{RS}, @code{OFS}, and @code{ORS}, which control input and -output formats before scanning the @value{DF}s. It is also useful for -controlling state if multiple passes are needed over a @value{DF}. For +output formats before scanning the data files. It is also useful for +controlling state if multiple passes are needed over a data file. For example: @cindex files, multiple passes over @@ -3811,13 +3804,13 @@ You may also use @code{"-"} to name standard input when reading files with @code{getline} (@pxref{Getline/File}). In addition, @command{gawk} allows you to specify the special -@value{FN} @file{/dev/stdin}, both on the command line and +file name @file{/dev/stdin}, both on the command line and with @code{getline}. Some other versions of @command{awk} also support this, but it is not standard. (Some operating systems provide a @file{/dev/stdin} file in the file system, however, @command{gawk} always processes -this @value{FN} itself.) +this file name itself.) @node Environment Variables @section The Environment Variables @command{gawk} Uses @@ -3847,7 +3840,7 @@ on the command-line with the @option{-f} option. In most @command{awk} implementations, you must supply a precise path name for each program file, unless the file is in the current directory. -But in @command{gawk}, if the @value{FN} supplied to the @option{-f} +But in @command{gawk}, if the file name supplied to the @option{-f} or @option{-i} options does not contain a @samp{/}, then @command{gawk} searches a list of directories (called the @dfn{search path}), one by one, looking for a @@ -3867,7 +3860,7 @@ though.} The search path feature is particularly useful for building libraries of useful @command{awk} functions. The library files can be placed in a standard directory in the default path and then specified on -the command line with a short @value{FN}. Otherwise, the full @value{FN} +the command line with a short file name. Otherwise, the full file name would have to be typed for each file. By using the @option{-i} option, or the @option{--source} and @option{-f} options, your command-line @@ -4067,7 +4060,7 @@ use @samp{@@include} followed by the name of the file to be included, enclosed in double quotes. @quotation NOTE -Keep in mind that this is a language construct and the @value{FN} cannot +Keep in mind that this is a language construct and the file name cannot be a string variable, but rather just a literal string in double quotes. @end quotation @@ -4092,7 +4085,7 @@ $ @kbd{gawk -f test3} @print{} This is file test3. @end example -The @value{FN} can, of course, be a pathname. For example: +The file name can, of course, be a pathname. For example: @example @@include "../io_funcs" @@ -4190,7 +4183,7 @@ they will @emph{not} be in the next release). @cindex @code{PROCINFO} array The process-related special files @file{/dev/pid}, @file{/dev/ppid}, @file{/dev/pgrpid}, and @file{/dev/user} were deprecated in @command{gawk} -3.1, but still worked. As of @value{PVERSION} 4.0, they are no longer +3.1, but still worked. As of version 4.0, they are no longer interpreted specially by @command{gawk}. (Use @code{PROCINFO} instead; see @ref{Auto-set}.) @@ -4446,39 +4439,39 @@ A literal backslash, @samp{\}. @cindex @code{\} (backslash), @code{\a} escape sequence @cindex backslash (@code{\}), @code{\a} escape sequence @item \a -The ``alert'' character, @kbd{@value{CTL}-g}, ASCII code 7 (BEL). +The ``alert'' character, @kbd{Ctrl-g}, ASCII code 7 (BEL). (This usually makes some sort of audible noise.) @cindex @code{\} (backslash), @code{\b} escape sequence @cindex backslash (@code{\}), @code{\b} escape sequence @item \b -Backspace, @kbd{@value{CTL}-h}, ASCII code 8 (BS). +Backspace, @kbd{Ctrl-h}, ASCII code 8 (BS). @cindex @code{\} (backslash), @code{\f} escape sequence @cindex backslash (@code{\}), @code{\f} escape sequence @item \f -Formfeed, @kbd{@value{CTL}-l}, ASCII code 12 (FF). +Formfeed, @kbd{Ctrl-l}, ASCII code 12 (FF). @cindex @code{\} (backslash), @code{\n} escape sequence @cindex backslash (@code{\}), @code{\n} escape sequence @item \n -Newline, @kbd{@value{CTL}-j}, ASCII code 10 (LF). +Newline, @kbd{Ctrl-j}, ASCII code 10 (LF). @cindex @code{\} (backslash), @code{\r} escape sequence @cindex backslash (@code{\}), @code{\r} escape sequence @item \r -Carriage return, @kbd{@value{CTL}-m}, ASCII code 13 (CR). +Carriage return, @kbd{Ctrl-m}, ASCII code 13 (CR). @cindex @code{\} (backslash), @code{\t} escape sequence @cindex backslash (@code{\}), @code{\t} escape sequence @item \t -Horizontal TAB, @kbd{@value{CTL}-i}, ASCII code 9 (HT). +Horizontal TAB, @kbd{Ctrl-i}, ASCII code 9 (HT). @c @cindex @command{awk} language, V.4 version @cindex @code{\} (backslash), @code{\v} escape sequence @cindex backslash (@code{\}), @code{\v} escape sequence @item \v -Vertical tab, @kbd{@value{CTL}-k}, ASCII code 11 (VT). +Vertical tab, @kbd{Ctrl-k}, ASCII code 11 (VT). @cindex @code{\} (backslash), @code{\}@var{nnn} escape sequence @cindex backslash (@code{\}), @code{\}@var{nnn} escape sequence @@ -4891,7 +4884,7 @@ constants, @command{gawk} did @emph{not} match interval expressions in regexps. -However, beginning with @value{PVERSION} 4.0, +However, beginning with version 4.0, @command{gawk} does match interval expressions by default. This is because compatibility with POSIX has become more important to most @command{gawk} users than compatibility with @@ -5487,7 +5480,7 @@ But a newline in a regexp constant works with no problem: $ @kbd{awk '$0 ~ /[ \t\n]/'} @kbd{here is a sample line} @print{} here is a sample line -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example @command{gawk} does not have this problem, and it isn't likely to @@ -5525,7 +5518,7 @@ But a newline in a regexp constant works with no problem: $ @kbd{awk '$0 ~ /[ \t\n]/'} @kbd{here is a sample line} @print{} here is a sample line -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example @command{gawk} does not have this problem, and it isn't likely to @@ -5601,7 +5594,7 @@ so far from the current input file. This value is stored in a built-in variable called @code{FNR}. It is reset to zero when a new file is started. Another built-in variable, @code{NR}, records the total -number of input records read so far from all @value{DF}s. It starts at zero, +number of input records read so far from all data files. It starts at zero, but is never automatically reset to zero. @cindex separators, for records @@ -5675,7 +5668,7 @@ $ @kbd{awk 'BEGIN @{ RS = "/" @}} @noindent Note that the entry for the @samp{camelot} BBS is not split. -In the original @value{DF} +In the original data file (@pxref{Sample Data Files}), the line looks like this: @@ -5688,7 +5681,7 @@ It has one baud rate only, so there are no slashes in the record, unlike the others which have two or more baud rates. In fact, this record is treated as part of the record for the @samp{core} BBS; the newline separating them in the output -is the original newline in the @value{DF}, not the one added by +is the original newline in the data file, not the one added by @command{awk} when it printed the record! @cindex record separators, changing @@ -5829,8 +5822,8 @@ In compatibility mode, only the first character of the value of <sidebar><title>@code{RS = "\0"} Is Not Portable</title> @end docbook -@cindex portability, @value{DF}s as single record -There are times when you might want to treat an entire @value{DF} as a +@cindex portability, data files as single record +There are times when you might want to treat an entire data file as a single record. The only way to make this happen is to give @code{RS} a value that you know doesn't occur in the input file. This is hard to do in a general way, such that a program always works for arbitrary @@ -5874,8 +5867,8 @@ record onto the end of the previous ones. @center @b{@code{RS = "\0"} Is Not Portable} -@cindex portability, @value{DF}s as single record -There are times when you might want to treat an entire @value{DF} as a +@cindex portability, data files as single record +There are times when you might want to treat an entire data file as a single record. The only way to make this happen is to give @code{RS} a value that you know doesn't occur in the input file. This is hard to do in a general way, such that a program always works for arbitrary @@ -7184,7 +7177,7 @@ appear in a row, they are considered one record separator. @cindex dark corner, multiline records There is an important difference between @samp{RS = ""} and @samp{RS = "\n\n+"}. In the first case, leading newlines in the input -@value{DF} are ignored, and if a file ends without extra blank lines +data file are ignored, and if a file ends without extra blank lines after the last record, the final newline is removed from the record. In the second case, this special processing is not done. @value{DARKCORNER} @@ -7219,7 +7212,7 @@ Another way to separate fields is to put each field on a separate line: to do this, just set the variable @code{FS} to the string @code{"\n"}. (This single character separator matches a single newline.) -A practical example of a @value{DF} organized this way might be a mailing +A practical example of a data file organized this way might be a mailing list, where each entry is separated by blank lines. Consider a mailing list in a file named @file{addresses}, which looks like this: @@ -7284,7 +7277,7 @@ value of @table @code @item RS == "\n" Records are separated by the newline character (@samp{\n}). In effect, -every line in the @value{DF} is a separate record, including blank lines. +every line in the data file is a separate record, including blank lines. This is the default. @item RS == @var{any single character} @@ -7490,7 +7483,7 @@ the value of @code{NF} do not change. @cindex operators, input/output Use @samp{getline < @var{file}} to read the next record from @var{file}. Here @var{file} is a string-valued expression that -specifies the @value{FN}. @samp{< @var{file}} is called a @dfn{redirection} +specifies the file name. @samp{< @var{file}} is called a @dfn{redirection} because it directs input to come from a different place. For example, the following program reads its input record from the file @file{secondary.input} when it @@ -7797,10 +7790,10 @@ system permits. @item An interesting side effect occurs if you use @code{getline} without a redirection inside a @code{BEGIN} rule. Because an unredirected @code{getline} -reads from the command-line @value{DF}s, the first @code{getline} command +reads from the command-line data files, the first @code{getline} command causes @command{awk} to set the value of @code{FILENAME}. Normally, @code{FILENAME} does not have a value inside @code{BEGIN} rules, because you -have not yet started to process the command-line @value{DF}s. +have not yet started to process the command-line data files. @value{DARKCORNER} (@xref{BEGIN/END}, also @pxref{Auto-set}.) @@ -8022,7 +8015,7 @@ For printing with specifications, you need the @code{printf} statement @cindex @code{printf} statement Besides basic and formatted printing, this @value{CHAPTER} also covers I/O redirections to files and pipes, introduces -the special @value{FN}s that @command{gawk} processes internally, +the special file names that @command{gawk} processes internally, and discusses the @code{close()} built-in function. @menu @@ -8823,9 +8816,9 @@ but they work identically for @code{printf}: @cindex operators, input/output @item print @var{items} > @var{output-file} This redirection prints the items into the output file named -@var{output-file}. The @value{FN} @var{output-file} can be any +@var{output-file}. The file name @var{output-file} can be any expression. Its value is changed to a string and then used as a -@value{FN} (@pxref{Expressions}). +file name (@pxref{Expressions}). When this type of redirection is used, the @var{output-file} is erased before the first output is written to it. Subsequent writes to the same @@ -8996,7 +8989,7 @@ open as many pipelines as the underlying operating system permits. A particularly powerful way to use redirection is to build command lines and pipe them into the shell, @command{sh}. For example, suppose you -have a list of files brought over from a system where all the @value{FN}s +have a list of files brought over from a system where all the file names are stored in uppercase, and you wish to rename them to have names in all lowercase. The following program is both simple and efficient: @@ -9028,7 +9021,7 @@ It then sends the list to the shell for execution. A particularly powerful way to use redirection is to build command lines and pipe them into the shell, @command{sh}. For example, suppose you -have a list of files brought over from a system where all the @value{FN}s +have a list of files brought over from a system where all the file names are stored in uppercase, and you wish to rename them to have names in all lowercase. The following program is both simple and efficient: @@ -9051,12 +9044,12 @@ It then sends the list to the shell for execution. @c ENDOFRANGE reout @node Special Files -@section Special @value{FFN}s in @command{gawk} +@section Special File Names in @command{gawk} @c STARTOFRANGE gfn -@cindex @command{gawk}, @value{FN}s in +@cindex @command{gawk}, file names in -@command{gawk} provides a number of special @value{FN}s that it interprets -internally. These @value{FN}s provide access to standard file descriptors +@command{gawk} provides a number of special file names that it interprets +internally. These file names provide access to standard file descriptors and TCP/IP networking. @menu @@ -9120,12 +9113,12 @@ that happens, writing to the screen is not correct. In fact, if terminal at all. Then opening @file{/dev/tty} fails. -@command{gawk} provides special @value{FN}s for accessing the three standard +@command{gawk} provides special file names for accessing the three standard streams. @value{COMMONEXT}. It also provides syntax for accessing -any other inherited open files. If the @value{FN} matches +any other inherited open files. If the file name matches one of these special names when @command{gawk} redirects input or output, -then it directly uses the stream that the @value{FN} stands for. -These special @value{FN}s work for all operating systems that @command{gawk} +then it directly uses the stream that the file name stands for. +These special file names work for all operating systems that @command{gawk} has been ported to, not just those that are POSIX-compliant: @cindex common extensions, @code{/dev/stdin} special file @@ -9134,7 +9127,7 @@ has been ported to, not just those that are POSIX-compliant: @cindex extensions, common@comma{} @code{/dev/stdin} special file @cindex extensions, common@comma{} @code{/dev/stdout} special file @cindex extensions, common@comma{} @code{/dev/stderr} special file -@cindex @value{FN}s, standard streams in @command{gawk} +@cindex file names, standard streams in @command{gawk} @cindex @code{/dev/@dots{}} special files (@command{gawk}) @cindex files, @code{/dev/@dots{}} special files @cindex @code{/dev/fd/@var{N}} special files @@ -9155,7 +9148,7 @@ the shell). Unless special pains are taken in the shell from which @command{gawk} is invoked, only descriptors 0, 1, and 2 are available. @end table -The @value{FN}s @file{/dev/stdin}, @file{/dev/stdout}, and @file{/dev/stderr} +The file names @file{/dev/stdin}, @file{/dev/stdout}, and @file{/dev/stderr} are aliases for @file{/dev/fd/0}, @file{/dev/fd/1}, and @file{/dev/fd/2}, respectively. However, they are more self-explanatory. The proper way to write an error message in a @command{gawk} program @@ -9165,14 +9158,14 @@ is to use @file{/dev/stderr}, like this: print "Serious error detected!" > "/dev/stderr" @end example -@cindex troubleshooting, quotes with @value{FN}s -Note the use of quotes around the @value{FN}. +@cindex troubleshooting, quotes with file names +Note the use of quotes around the file name. Like any other redirection, the value must be a string. It is a common error to omit the quotes, which leads to confusing results. @c Exercise: What does it do? :-) -Finally, using the @code{close()} function on a @value{FN} of the +Finally, using the @code{close()} function on a file name of the form @code{"/dev/fd/@var{N}"}, for file descriptor numbers above two, does actually close the given file descriptor. @@ -9188,7 +9181,7 @@ versions of @command{awk}. @command{gawk} programs can open a two-way TCP/IP connection, acting as either a client or a server. -This is done using a special @value{FN} of the form: +This is done using a special file name of the form: @example @file{/@var{net-type}/@var{protocol}/@var{local-port}/@var{remote-host}/@var{remote-port}} @@ -9198,7 +9191,7 @@ The @var{net-type} is one of @samp{inet}, @samp{inet4} or @samp{inet6}. The @var{protocol} is one of @samp{tcp} or @samp{udp}, and the other fields represent the other essential pieces of information for making a networking connection. -These @value{FN}s are used with the @samp{|&} operator for communicating +These file names are used with the @samp{|&} operator for communicating with a coprocess (@pxref{Two-way I/O}). This is an advanced feature, mentioned here only for completeness. @@ -9206,21 +9199,21 @@ Full discussion is delayed until @ref{TCP/IP Networking}. @node Special Caveats -@subsection Special @value{FFN} Caveats +@subsection Special File Name Caveats Here is a list of things to bear in mind when using the -special @value{FN}s that @command{gawk} provides: +special file names that @command{gawk} provides: @itemize @bullet -@cindex compatibility mode (@command{gawk}), @value{FN}s -@cindex @value{FN}s, in compatibility mode +@cindex compatibility mode (@command{gawk}), file names +@cindex file names, in compatibility mode @item -Recognition of these special @value{FN}s is disabled if @command{gawk} is in +Recognition of these special file names is disabled if @command{gawk} is in compatibility mode (@pxref{Options}). @item @command{gawk} @emph{always} -interprets these special @value{FN}s. +interprets these special file names. For example, using @samp{/dev/fd/4} for output actually writes on file descriptor 4, and not on a new file descriptor that is @code{dup()}'ed from file descriptor 4. Most of @@ -9243,7 +9236,7 @@ Doing so results in unpredictable behavior. @cindex coprocesses, closing @cindex @code{getline} command, coprocesses@comma{} using from -If the same @value{FN} or the same shell command is used with @code{getline} +If the same file name or the same shell command is used with @code{getline} more than once during the execution of an @command{awk} program (@pxref{Getline}), the file is opened (or the command is executed) the first time only. @@ -9252,7 +9245,7 @@ The next time the same file or command is used with @code{getline}, another record is read from it, and so on. Similarly, when a file or pipe is opened for output, @command{awk} remembers -the @value{FN} or command associated with it, and subsequent +the file name or command associated with it, and subsequent writes to the same file or command are appended to the previous writes. The file or pipe stays open until @command{awk} exits. @@ -9294,7 +9287,7 @@ file or command, or the next @code{print} or @code{printf} to that file or command, reopens the file or reruns the command. Because the expression that you use to close a file or pipeline must exactly match the expression used to open the file or run the command, -it is good practice to use a variable to store the @value{FN} or command. +it is good practice to use a variable to store the file name or command. The previous example becomes the following: @example @@ -9343,7 +9336,7 @@ a separate message. @cindex portability, @code{close()} function and If you use more files than the system allows you to have open, @command{gawk} attempts to multiplex the available open files among -your @value{DF}s. @command{gawk}'s ability to do this depends upon the +your data files. @command{gawk}'s ability to do this depends upon the facilities of your operating system, so it may not always work. It is therefore both good practice and good portability advice to always use @code{close()} on your files when you are done with them. @@ -9948,7 +9941,7 @@ as in the following: @noindent the variable is set at the very beginning, even before the @code{BEGIN} rules execute. The @option{-v} option and its assignment -must precede all the @value{FN} arguments, as well as the program text. +must precede all the file name arguments, as well as the program text. (@xref{Options}, for more information about the @option{-v} option.) Otherwise, the variable assignment is performed at a time determined by @@ -11620,7 +11613,7 @@ $ @kbd{awk '@{ print "The square root of", $1, "is", sqrt($1) @}'} @print{} The square root of 3 is 1.73205 @kbd{5} @print{} The square root of 5 is 2.23607 -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example A function can also have side effects, such as assigning @@ -13142,11 +13135,11 @@ The @code{nextfile} statement is similar to the @code{next} statement. However, instead of abandoning processing of the current record, the @code{nextfile} statement instructs @command{awk} to stop processing the -current @value{DF}. +current data file. Upon execution of the @code{nextfile} statement, @code{FILENAME} is -updated to the name of the next @value{DF} listed on the command line, +updated to the name of the next data file listed on the command line, @code{FNR} is reset to one, and processing starts over with the first rule in the program. @@ -13155,10 +13148,10 @@ then the code in any @code{END} rules is executed. An exception to this is when @code{nextfile} is invoked during execution of any statement in an @code{END} rule; In this case, it causes the program to stop immediately. @xref{BEGIN/END}. -The @code{nextfile} statement is useful when there are many @value{DF}s +The @code{nextfile} statement is useful when there are many data files to process but it isn't necessary to process every record in every file. Without @code{nextfile}, -in order to move on to the next @value{DF}, a program +in order to move on to the next data file, a program would have to continue scanning the unwanted records. The @code{nextfile} statement accomplishes this much more efficiently. @@ -13625,17 +13618,17 @@ about how @command{awk} uses these variables. @cindex differences in @command{awk} and @command{gawk}, @code{ARGIND} variable @item ARGIND # The index in @code{ARGV} of the current file being processed. -Every time @command{gawk} opens a new @value{DF} for processing, it sets -@code{ARGIND} to the index in @code{ARGV} of the @value{FN}. +Every time @command{gawk} opens a new data file for processing, it sets +@code{ARGIND} to the index in @code{ARGV} of the file name. When @command{gawk} is processing the input files, @samp{FILENAME == ARGV[ARGIND]} is always true. @cindex files, processing@comma{} @code{ARGIND} variable and This variable is useful in file processing; it allows you to tell how far -along you are in the list of @value{DF}s as well as to distinguish between -successive instances of the same @value{FN} on the command line. +along you are in the list of data files as well as to distinguish between +successive instances of the same file name on the command line. -@cindex @value{FN}s, distinguishing +@cindex file names, distinguishing While you can change the value of @code{ARGIND} within your @command{awk} program, @command{gawk} automatically sets it to a new value when the next file is opened. @@ -13697,14 +13690,14 @@ it is not special. @cindex dark corner, @code{FILENAME} variable @item FILENAME The name of the file that @command{awk} is currently reading. -When no @value{DF}s are listed on the command line, @command{awk} reads +When no data files are listed on the command line, @command{awk} reads from the standard input and @code{FILENAME} is set to @code{"-"}. @code{FILENAME} is changed each time a new file is read (@pxref{Reading Files}). Inside a @code{BEGIN} rule, the value of @code{FILENAME} is @code{""}, since there are no input files being processed yet.@footnote{Some early implementations of Unix @command{awk} initialized -@code{FILENAME} to @code{"-"}, even if there were @value{DF}s to be +@code{FILENAME} to @code{"-"}, even if there were data files to be processed. This behavior was incorrect and should not be relied upon in your programs.} @value{DARKCORNER} @@ -14127,11 +14120,11 @@ additional files to be read. If the value of @code{ARGC} is decreased, that eliminates input files from the end of the list. By recording the old value of @code{ARGC} elsewhere, a program can treat the eliminated arguments as -something other than @value{FN}s. +something other than file names. To eliminate a file from the middle of the list, store the null string (@code{""}) into @code{ARGV} in place of the file's name. As a -special feature, @command{awk} ignores @value{FN}s that have been +special feature, @command{awk} ignores file names that have been replaced with the null string. Another option is to use the @code{delete} statement to remove elements from @@ -16561,17 +16554,17 @@ _bigskip} The only case where the difference is noticeable is the last one: @samp{\\\\} is seen as @samp{\\} and produces @samp{\} instead of @samp{\\}. -Starting with @value{PVERSION} 3.1.4, @command{gawk} followed the POSIX rules +Starting with version 3.1.4, @command{gawk} followed the POSIX rules when @option{--posix} is specified (@pxref{Options}). Otherwise, it continued to follow the 1996 proposed rules, since that had been its behavior for many years. -When @value{PVERSION} 4.0.0 was released, the @command{gawk} maintainer +When version 4.0.0 was released, the @command{gawk} maintainer made the POSIX rules the default, breaking well over a decade's worth of backwards compatibility.@footnote{This was rather naive of him, despite there being a note in this section indicating that the next major version would move to the POSIX rules.} Needless to say, this was a bad idea, -and as of @value{PVERSION} 4.0.1, @command{gawk} resumed its historical +and as of version 4.0.1, @command{gawk} resumed its historical behavior, and only follows the POSIX rules when @option{--posix} is given. The rules for @code{gensub()} are considerably simpler. At the runtime @@ -16843,7 +16836,7 @@ $ @kbd{awk '@{ print $1 + $2 @}'} @print{} 2 @kbd{2 3} @print{} 5 -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example @noindent @@ -16854,13 +16847,13 @@ with this example: $ @kbd{awk '@{ print $1 + $2 @}' | cat} @kbd{1 1} @kbd{2 3} -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @print{} 2 @print{} 5 @end example @noindent -Here, no output is printed until after the @kbd{@value{CTL}-d} is typed, because +Here, no output is printed until after the @kbd{Ctrl-d} is typed, because it is all buffered and sent down the pipe to @command{cat} in one shot. @docbook @@ -16894,7 +16887,7 @@ $ @kbd{awk '@{ print $1 + $2 @}'} @print{} 2 @kbd{2 3} @print{} 5 -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example @noindent @@ -16905,13 +16898,13 @@ with this example: $ @kbd{awk '@{ print $1 + $2 @}' | cat} @kbd{1 1} @kbd{2 3} -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @print{} 2 @print{} 5 @end example @noindent -Here, no output is printed until after the @kbd{@value{CTL}-d} is typed, because +Here, no output is printed until after the @kbd{Ctrl-d} is typed, because it is all buffered and sent down the pipe to @command{cat} in one shot. @end cartouche @end ifnotdocbook @@ -19296,7 +19289,7 @@ An @code{END} rule is automatically added to the program calling @code{assert()}. Normally, if a program consists of just a @code{BEGIN} rule, the input files and/or standard input are not read. However, now that the program has an @code{END} rule, @command{awk} -attempts to read the input @value{DF}s or standard input +attempts to read the input data files or standard input (@pxref{Using BEGIN/END}), most likely causing the program to hang as it waits for input. @@ -19706,16 +19699,16 @@ allowed the user to supply an optional timestamp value to use instead of the current time. @node Data File Management -@section @value{DDF} Management +@section Data File Management @c STARTOFRANGE dataf @cindex files, managing @c STARTOFRANGE libfdataf -@cindex libraries of @command{awk} functions, managing, @value{DF}s +@cindex libraries of @command{awk} functions, managing, data files @c STARTOFRANGE flibdataf -@cindex functions, library, managing @value{DF}s +@cindex functions, library, managing data files This @value{SECTION} presents functions that are useful for managing -command-line @value{DF}s. +command-line data files. @menu * Filetrans Function:: A function for handling data file transitions. @@ -19726,16 +19719,16 @@ command-line @value{DF}s. @end menu @node Filetrans Function -@subsection Noting @value{DDF} Boundaries +@subsection Noting Data File Boundaries -@cindex files, managing, @value{DF} boundaries +@cindex files, managing, data file boundaries @cindex files, initialization and cleanup The @code{BEGIN} and @code{END} rules are each executed exactly once at the beginning and end of your @command{awk} program, respectively (@pxref{BEGIN/END}). We (the @command{gawk} authors) once had a user who mistakenly thought that the -@code{BEGIN} rule is executed at the beginning of each @value{DF} and the -@code{END} rule is executed at the end of each @value{DF}. +@code{BEGIN} rule is executed at the beginning of each data file and the +@code{END} rule is executed at the end of each data file. When informed that this was not the case, the user requested that we add new special @@ -19746,7 +19739,7 @@ Adding these special patterns to @command{gawk} wasn't necessary; the job can be done cleanly in @command{awk} itself, as illustrated by the following library program. It arranges to call two user-supplied functions, @code{beginfile()} and -@code{endfile()}, at the beginning and end of each @value{DF}. +@code{endfile()}, at the beginning and end of each data file. Besides solving the problem in only nine(!) lines of code, it does so @emph{portably}; this works with any implementation of @command{awk}: @@ -19777,17 +19770,17 @@ This file must be loaded before the user's ``main'' program, so that the rule it supplies is executed first. This rule relies on @command{awk}'s @code{FILENAME} variable that -automatically changes for each new @value{DF}. The current @value{FN} is +automatically changes for each new data file. The current file name is saved in a private variable, @code{_oldfilename}. If @code{FILENAME} does -not equal @code{_oldfilename}, then a new @value{DF} is being processed and +not equal @code{_oldfilename}, then a new data file is being processed and it is necessary to call @code{endfile()} for the old file. Because @code{endfile()} should only be called if a file has been processed, the program first checks to make sure that @code{_oldfilename} is not the null -string. The program then assigns the current @value{FN} to +string. The program then assigns the current file name to @code{_oldfilename} and calls @code{beginfile()} for the file. Because, like all @command{awk} variables, @code{_oldfilename} is initialized to the null string, this rule executes correctly even for the -first @value{DF}. +first data file. The program also supplies an @code{END} rule to do the final processing for the last file. Because this @code{END} rule comes before any @code{END} rules @@ -19796,7 +19789,7 @@ again the value of multiple @code{BEGIN} and @code{END} rules should be clear. @cindex @code{beginfile()} user-defined function @cindex @code{endfile()} user-defined function -If the same @value{DF} occurs twice in a row on the command line, then +If the same data file occurs twice in a row on the command line, then @code{endfile()} and @code{beginfile()} are not executed at the end of the first pass and at the beginning of the second pass. The following version solves the problem: @@ -19940,12 +19933,12 @@ The @code{rewind()} function also relies on the @code{nextfile} keyword (@pxref{Nextfile Statement}). @node File Checking -@subsection Checking for Readable @value{DDF}s +@subsection Checking for Readable Data Files -@cindex troubleshooting, readable @value{DF}s -@cindex readable @value{DF}s@comma{} checking +@cindex troubleshooting, readable data files +@cindex readable data files@comma{} checking @cindex files, skipping -Normally, if you give @command{awk} a @value{DF} that isn't readable, +Normally, if you give @command{awk} a data file that isn't readable, it stops with a fatal error. There are times when you might want to just ignore such files and keep going. You can do this by prepending the following program to your @command{awk} @@ -19994,15 +19987,15 @@ This is a by-product of @command{awk}'s implicit read-a-record-and-match-against-the-rules loop: when @command{awk} tries to read a record from an empty file, it immediately receives an end of file indication, closes the file, and proceeds on to the next -command-line @value{DF}, @emph{without} executing any user-level +command-line data file, @emph{without} executing any user-level @command{awk} program code. Using @command{gawk}'s @code{ARGIND} variable (@pxref{Built-in Variables}), it is possible to detect when an empty -@value{DF} has been skipped. Similar to the library file presented +data file has been skipped. Similar to the library file presented in @ref{Filetrans Function}, the following library file calls a function named @code{zerofile()} that the user must provide. The arguments passed are -the @value{FN} and the position in @code{ARGV} where it was found: +the file name and the position in @code{ARGV} where it was found: @cindex @code{zerofile.awk} program @example @@ -20090,15 +20083,15 @@ END @{ @end ignore @node Ignoring Assigns -@subsection Treating Assignments as @value{FFN}s +@subsection Treating Assignments as File Names @cindex assignments as filenames @cindex filenames, assignments as Occasionally, you might not want @command{awk} to process command-line variable assignments (@pxref{Assignment Options}). -In particular, if you have a @value{FN} that contain an @samp{=} character, -@command{awk} treats the @value{FN} as an assignment, and does not process it. +In particular, if you have a file name that contain an @samp{=} character, +@command{awk} treats the file name as an assignment, and does not process it. Some users have suggested an additional command-line option for @command{gawk} to disable command-line assignments. However, some simple programming with @@ -20142,7 +20135,7 @@ awk -v No_command_assign=1 -f noassign.awk -f yourprog.awk * The function works by looping through the arguments. It prepends @samp{./} to any argument that matches the form -of a variable assignment, turning that argument into a @value{FN}. +of a variable assignment, turning that argument into a file name. The use of @code{No_command_assign} allows you to disable command-line assignments at invocation time, by giving the variable a true value. @@ -20501,7 +20494,7 @@ After @code{getopt()} is through, it is the responsibility of the user level code to clear out all the elements of @code{ARGV} from 1 to @code{Optind}, so that @command{awk} does not try to process the command-line options -as @value{FN}s. +as file names. @end quotation Several of the sample programs presented in @@ -21375,7 +21368,7 @@ awk -f @var{program} -- @var{options} @var{files} @noindent Here, @var{program} is the name of the @command{awk} program (such as @file{cut.awk}), @var{options} are any command-line options for the -program that start with a @samp{-}, and @var{files} are the actual @value{DF}s. +program that start with a @samp{-}, and @var{files} are the actual data files. If your system supports the @samp{#!} executable interpreter mechanism (@pxref{Executable Scripts}), @@ -21580,7 +21573,7 @@ spaces. Also remember that after @code{getopt()} is through we have to clear out all the elements of @code{ARGV} from 1 to @code{Optind}, so that @command{awk} does not try to process the command-line options -as @value{FN}s. +as file names. After dealing with the command-line options, the program verifies that the options make sense. Only one or the other of @option{-c} and @option{-f} @@ -21776,8 +21769,8 @@ egrep @r{[} @var{options} @r{]} '@var{pattern}' @var{files} @dots{} The @var{pattern} is a regular expression. In typical usage, the regular expression is quoted to prevent the shell from expanding any of the -special characters as @value{FN} wildcards. Normally, @command{egrep} -prints the lines that matched. If multiple @value{FN}s are provided on +special characters as file name wildcards. Normally, @command{egrep} +prints the lines that matched. If multiple file names are provided on the command line, each output line is preceded by the name of the file and a colon. @@ -21868,7 +21861,7 @@ pattern is supplied with @option{-e}, the first nonoption on the command line is used. The @command{awk} command-line arguments up to @code{ARGV[Optind]} are cleared, so that @command{awk} won't try to process them as files. If no files are specified, the standard input is used, and if multiple files are -specified, we make sure to note this so that the @value{FN}s can precede the +specified, we make sure to note this so that the file names can precede the matched lines in the output: @example @@ -21966,9 +21959,9 @@ A number of additional tests are made, but they are only done if we are not counting lines. First, if the user only wants exit status (@code{no_print} is true), then it is enough to know that @emph{one} line in this file matched, and we can skip on to the next file with -@code{nextfile}. Similarly, if we are only printing @value{FN}s, we can -print the @value{FN}, and then skip to the next file with @code{nextfile}. -Finally, each line is printed, with a leading @value{FN} and colon +@code{nextfile}. Similarly, if we are only printing file names, we can +print the file name, and then skip to the next file with @code{nextfile}. +Finally, each line is printed, with a leading file name and colon if necessary: @cindex @code{!} (exclamation point), @code{!} operator @@ -22216,7 +22209,7 @@ number of lines in each file, supply a number on the command line preceded with a minus; e.g., @samp{-500} for files with 500 lines in them instead of 1000. To change the name of the output files to something like @file{myfileaa}, @file{myfileab}, and so on, supply an additional -argument that specifies the @value{FN} prefix. +argument that specifies the file name prefix. Here is a version of @command{split} in @command{awk}. It uses the @code{ord()} and @code{chr()} functions presented in @@ -22226,8 +22219,8 @@ The program first sets its defaults, and then tests to make sure there are not too many arguments. It then looks at each argument in turn. The first argument could be a minus sign followed by a number. If it is, this happens to look like a negative number, so it is made positive, and that is the -count of lines. The data @value{FN} is skipped over and the final argument -is used as the prefix for the output @value{FN}s: +count of lines. The data file name is skipped over and the final argument +is used as the prefix for the output file names: @cindex @code{split.awk} program @example @@ -22276,7 +22269,7 @@ BEGIN @{ The next rule does most of the work. @code{tcount} (temporary count) tracks how many lines have been printed to the output file so far. If it is greater than @code{count}, it is time to close the current file and start a new one. -@code{s1} and @code{s2} track the current suffixes for the @value{FN}. If +@code{s1} and @code{s2} track the current suffixes for the file name. If they are both @samp{z}, the file is just too big. Otherwise, @code{s1} moves to the next letter in the alphabet and @code{s2} starts over again at @samp{a}: @@ -22364,13 +22357,13 @@ The @code{BEGIN} rule first makes a copy of all the command-line arguments into an array named @code{copy}. @code{ARGV[0]} is not copied, since it is not needed. @code{tee} cannot use @code{ARGV} directly, since @command{awk} attempts to -process each @value{FN} in @code{ARGV} as input data. +process each file name in @code{ARGV} as input data. @cindex flag variables If the first argument is @option{-a}, then the flag variable @code{append} is set to true, and both @code{ARGV[1]} and @code{copy[1]} are deleted. If @code{ARGC} is less than two, then no -@value{FN}s were supplied and @code{tee} prints a usage message and exits. +file names were supplied and @code{tee} prints a usage message and exits. Finally, @command{awk} is forced to read the standard input by setting @code{ARGV[1]} to @code{"-"} and @code{ARGC} to two: @@ -22832,7 +22825,7 @@ BEGIN @{ @end example The @code{beginfile()} function is simple; it just resets the counts of lines, -words, and characters to zero, and saves the current @value{FN} in +words, and characters to zero, and saves the current file name in @code{fname}: @example @@ -22854,7 +22847,7 @@ you will see that @code{FNR} has already been reset by the time @code{endfile()} is called.} It then prints out those numbers for the file that was just read. It relies on @code{beginfile()} to reset the -numbers for the following @value{DF}: +numbers for the following data file: @c FIXME: ONE DAY: make the above footnote an exercise, @c instead of giving away the answer. @@ -23204,7 +23197,7 @@ including Solaris, @end ifset @command{tr} may require that the lists be written as range expressions enclosed in square brackets (@samp{[a-z]}) and quoted, -to prevent the shell from attempting a @value{FN} expansion. This is +to prevent the shell from attempting a file name expansion. This is not a feature.} When processing the input, the first character in the first list is replaced with the first character in the second list, the second character in the first list is replaced with the second @@ -23602,7 +23595,7 @@ The @command{uniq} program (@pxref{Uniq Program}), removes duplicate lines from @emph{sorted} data. -Suppose, however, you need to remove duplicate lines from a @value{DF} but +Suppose, however, you need to remove duplicate lines from a data file but that you want to preserve the order the lines are in. A good example of this might be a shell history file. The history file keeps a copy of all the commands you have entered, and it is not unusual to repeat a command @@ -23821,7 +23814,7 @@ screen. @end ifnottex The second rule handles moving data into files. It verifies that a -@value{FN} is given in the directive. If the file named is not the +file name is given in the directive. If the file named is not the current file, then the current file is closed. Keeping the current file open until a new file is encountered allows the use of the @samp{>} redirection for printing the contents, keeping open file management @@ -23903,7 +23896,7 @@ subsequent output is appended to the file (@pxref{Redirection}). This makes it easy to mix program text and explanatory prose for the same sample source file (as has been done here!) without any hassle. The file is -only closed when a new data @value{FN} is encountered or at the end of the +only closed when a new data file name is encountered or at the end of the input file. Finally, the function @code{@w{unexpected_eof()}} prints an appropriate @@ -23955,7 +23948,7 @@ Here, @samp{s/old/new/g} tells @command{sed} to look for the regexp The following program, @file{awksed.awk}, accepts at least two command-line arguments: the pattern to look for and the text to replace it with. Any -additional arguments are treated as data @value{FN}s to process. If none +additional arguments are treated as data file names to process. If none are provided, the standard input is used: @cindex Brennan, Michael @@ -24028,7 +24021,7 @@ The @code{BEGIN} rule handles the setup, checking for the right number of arguments and calling @code{usage()} if there is a problem. Then it sets @code{RS} and @code{ORS} from the command-line arguments and sets @code{ARGV[1]} and @code{ARGV[2]} to the null string, so that they are -not treated as @value{FN}s +not treated as file names (@pxref{ARGC and ARGV}). The @code{usage()} function prints an error message and exits. @@ -24126,7 +24119,7 @@ Literal text, provided with @option{--source} or @option{--source=}. This text is just appended directly. @item -Source @value{FN}s, provided with @option{-f}. We use a neat trick and append +Source file names, provided with @option{-f}. We use a neat trick and append @samp{@@include @var{filename}} to the shell variable's contents. Since the file-inclusion program works the way @command{gawk} does, this gets the text of the file included into the program at the correct point. @@ -24139,7 +24132,7 @@ shell variable. @item Run the expanded program with @command{gawk} and any other original command-line -arguments that the user supplied (such as the data @value{FN}s). +arguments that the user supplied (such as the data file names). @end enumerate This program uses shell variables extensively: for storing command-line arguments, @@ -24170,7 +24163,7 @@ programming trick. Don't worry about it if you are not familiar with These are saved and passed on to @command{gawk}. @item -f@r{,} --file@r{,} --file=@r{,} -Wfile= -The @value{FN} is appended to the shell variable @code{program} with an +The file name is appended to the shell variable @code{program} with an @samp{@@include} statement. The @command{expr} utility is used to remove the leading option part of the argument (e.g., @samp{--file=}). @@ -24294,10 +24287,10 @@ is stored in the shell variable @code{expand_prog}. Doing this keeps the shell script readable. The @command{awk} program reads through the user's program, one line at a time, using @code{getline} (@pxref{Getline}). The input -@value{FN}s and @samp{@@include} statements are managed using a stack. -As each @samp{@@include} is encountered, the current @value{FN} is +file names and @samp{@@include} statements are managed using a stack. +As each @samp{@@include} is encountered, the current file name is ``pushed'' onto the stack and the file named in the @samp{@@include} -directive becomes the current @value{FN}. As each file is finished, +directive becomes the current file name. As each file is finished, the stack is ``popped,'' and the previous input file becomes the current input file again. The process is started by making the original file the first one on the stack. @@ -24306,16 +24299,16 @@ The @code{pathto()} function does the work of finding the full path to a file. It simulates @command{gawk}'s behavior when searching the @env{AWKPATH} environment variable (@pxref{AWKPATH Variable}). -If a @value{FN} has a @samp{/} in it, no path search is done. -Similarly, if the @value{FN} is @code{"-"}, then that string is +If a file name has a @samp{/} in it, no path search is done. +Similarly, if the file name is @code{"-"}, then that string is used as-is. Otherwise, -the @value{FN} is concatenated with the name of each directory in -the path, and an attempt is made to open the generated @value{FN}. +the file name is concatenated with the name of each directory in +the path, and an attempt is made to open the generated file name. The only way to test if a file can be read in @command{awk} is to go ahead and try to read it with @code{getline}; this is what @code{pathto()} does.@footnote{On some very old versions of @command{awk}, the test @samp{getline junk < t} can loop forever if the file exists but is empty. -Caveat emptor.} If the file can be read, it is closed and the @value{FN} +Caveat emptor.} If the file can be read, it is closed and the file name is returned: @ignore @@ -24373,14 +24366,14 @@ BEGIN @{ The stack is initialized with @code{ARGV[1]}, which will be @file{/dev/stdin}. The main loop comes next. Input lines are read in succession. Lines that do not start with @samp{@@include} are printed verbatim. -If the line does start with @samp{@@include}, the @value{FN} is in @code{$2}. +If the line does start with @samp{@@include}, the file name is in @code{$2}. @code{pathto()} is called to generate the full path. If it cannot, then the program prints an error message and continues. The next thing to check is if the file is included already. The -@code{processed} array is indexed by the full @value{FN} of each included +@code{processed} array is indexed by the full file name of each included file and it tracks this information for us. If the file is -seen again, a warning message is printed. Otherwise, the new @value{FN} is +seen again, a warning message is printed. Otherwise, the new file name is pushed onto the stack and processing continues. Finally, when @code{getline} encounters the end of the input file, the file @@ -24458,10 +24451,10 @@ options and command-line arguments that the user supplied. @c this causes more problems than it solves, so leave it out. @ignore -The special file @file{/dev/null} is passed as a @value{DF} to @command{gawk} +The special file @file{/dev/null} is passed as a data file to @command{gawk} to handle an interesting case. Suppose that the user's program only has -a @code{BEGIN} rule and there are no @value{DF}s to read. -The program should exit without reading any @value{DF}s. +a @code{BEGIN} rule and there are no data files to read. +The program should exit without reading any data files. However, suppose that an included library file defines an @code{END} rule of its own. In this case, @command{gawk} will hang, reading standard input. In order to avoid this, @file{/dev/null} is explicitly added to the @@ -25555,10 +25548,10 @@ another process on another system across an IP network connection. You can think of this as just a @emph{very long} two-way pipeline to a coprocess. The way @command{gawk} decides that you want to use TCP/IP networking is -by recognizing special @value{FN}s that begin with one of @samp{/inet/}, +by recognizing special file names that begin with one of @samp{/inet/}, @samp{/inet4/} or @samp{/inet6}. -The full syntax of the special @value{FN} is +The full syntax of the special file name is @file{/@var{net-type}/@var{protocol}/@var{local-port}/@var{remote-host}/@var{remote-port}}. The components are: @@ -25927,8 +25920,8 @@ the case of the @code{INT} signal, @command{gawk} exits. This is because these systems don't support the @command{kill} command, so the only signals you can deliver to a program are those generated by the keyboard. The @code{INT} signal is generated by the -@kbd{@value{CTL}-@key{C}} or @kbd{@value{CTL}-@key{BREAK}} key, while the -@code{QUIT} signal is generated by the @kbd{@value{CTL}-@key{\}} key. +@kbd{Ctrl-@key{C}} or @kbd{Ctrl-@key{BREAK}} key, while the +@code{QUIT} signal is generated by the @kbd{Ctrl-@key{\}} key. Finally, @command{gawk} also accepts another option, @option{--pretty-print}. When called this way, @command{gawk} ``pretty prints'' the program into @@ -26720,7 +26713,7 @@ complete detail in @cite{GNU gettext tools}.) @end ifnotinfo As of this writing, the latest version of GNU @code{gettext} is -@uref{ftp://ftp.gnu.org/gnu/gettext/gettext-0.18.2.1.tar.gz, @value{PVERSION} 0.18.2.1}. +@uref{ftp://ftp.gnu.org/gnu/gettext/gettext-0.18.2.1.tar.gz, version 0.18.2.1}. If a translation of @command{gawk}'s messages exists, then @command{gawk} produces usage messages, warnings, @@ -27600,7 +27593,7 @@ functions which called the one you are in. The commands for doing this are: Print a backtrace of all function calls (stack frames), or innermost @var{count} frames if @var{count} > 0. Print the outermost @var{count} frames if @var{count} < 0. The backtrace displays the name and arguments to each -function, the source @value{FN}, and the line number. +function, the source file name, and the line number. @cindex debugger commands, @code{down} @cindex @code{down} debugger command @@ -27733,7 +27726,7 @@ Turn instruction tracing on or off. The default is @code{off}. @end table @item @code{save} @var{filename} -Save the commands from the current session to the given @value{FN}, +Save the commands from the current session to the given file name, so that they can be replayed using the @command{source} command. @item @code{source} @var{filename} @@ -27901,8 +27894,8 @@ features. The following types of completion are available: @item Command completion Command names. -@item Source @value{FN} completion -Source @value{FN}s. Relevant commands are +@item Source file name completion +Source file names. Relevant commands are @code{break}, @code{clear}, @code{list}, @@ -28161,7 +28154,7 @@ $ @kbd{awk '@{ printf("%010d\n", $1 * 100) @}'} @print{} 0000051580 515.82 @print{} 0000051582 -@kbd{@value{CTL}-d} +@kbd{Ctrl-d} @end example @noindent @@ -33231,7 +33224,7 @@ Special files in I/O redirections: @itemize @minus{} @item The @file{/dev/stdin}, @file{/dev/stdout}, @file{/dev/stderr} and -@file{/dev/fd/@var{N}} special @value{FN}s +@file{/dev/fd/@var{N}} special file names (@pxref{Special Files}). @item @@ -33455,7 +33448,7 @@ long options @item Support for the following obsolete systems was removed from the code -and the documentation for @command{gawk} @value{PVERSION} 4.0: +and the documentation for @command{gawk} version 4.0: @c nested table @itemize @minus @@ -33969,7 +33962,7 @@ Extracting the archive creates a directory named @file{gawk-@value{VERSION}.@value{PATCHLEVEL}} in the current directory. -The distribution @value{FN} is of the form +The distribution file name is of the form @file{gawk-@var{V}.@var{R}.@var{P}.tar.gz}. The @var{V} represents the major version of @command{gawk}, the @var{R} represents the current release of version @var{V}, and @@ -34821,7 +34814,7 @@ provides information about both the @command{gawk} implementation and the The logical name @samp{AWK_LIBRARY} can designate a default location for @command{awk} program files. For the @option{-f} option, if the specified -@value{FN} has no device or directory path information in it, @command{gawk} +file name has no device or directory path information in it, @command{gawk} looks in the current directory first, then in the directory specified by the translation of @samp{AWK_LIBRARY} if the file is not found. If, after searching in both directories, the file still is not found, @@ -34854,7 +34847,7 @@ One side effect of dual command-line parsing is that if there is only a single parameter (as in the quoted string program above), the command becomes ambiguous. To work around this, the normally optional @option{--} flag is required to force Unix-style parsing rather than @code{DCL} parsing. If any -other dash-type options (or multiple parameters such as @value{DF}s to +other dash-type options (or multiple parameters such as data files to process) are present, there is no ambiguity and @option{--} can be omitted. @c @cindex directory search @@ -34915,7 +34908,7 @@ define a symbol, as follows: $ @kbd{gawk :== $sys$common:[syshlp.examples.tcpip.snmp]gawk.exe} @end example -This is apparently @value{PVERSION} 2.15.6, which is extremely old. We +This is apparently version 2.15.6, which is extremely old. We recommend compiling and using the current version. @c ENDOFRANGE opgawx @@ -34944,8 +34937,8 @@ what you're trying to do. If it's not clear whether you should be able to do something or not, report that too; it's a bug in the documentation! Before reporting a bug or trying to fix it yourself, try to isolate it -to the smallest possible @command{awk} program and input @value{DF} that -reproduces the problem. Then send us the program and @value{DF}, +to the smallest possible @command{awk} program and input data file that +reproduces the problem. Then send us the program and data file, some idea of what kind of Unix system you're using, the compiler you used to compile @command{gawk}, and the exact results @command{gawk} gave you. Also say what you expected to occur; this helps @@ -36097,11 +36090,11 @@ to any of the above. @ref{Dynamic Extensions}, describes the supported API and mechanisms for writing extensions for @command{gawk}. This API was introduced -in @value{PVERSION} 4.1. However, for many years @command{gawk} +in version 4.1. However, for many years @command{gawk} provided an extension mechanism that required knowledge of @command{gawk} internals and that was not as well designed. -In order to provide a transition period, @command{gawk} @value{PVERSION} +In order to provide a transition period, @command{gawk} version 4.1 continues to support the original extension mechanism. This will be true for the life of exactly one major release. This support will be withdrawn, and removed from the source code, at the next major @@ -37069,7 +37062,7 @@ numeric values. It is the C type @code{float}. The character generated by hitting the space bar on the keyboard. @item Special File -A @value{FN} interpreted internally by @command{gawk}, instead of being handed +A file name interpreted internally by @command{gawk}, instead of being handed directly to the underlying operating system---for example, @file{/dev/stderr}. (@xref{Special Files}.) |