856 lines
19 KiB
Groff
856 lines
19 KiB
Groff
.\" $OpenBSD: awk.1,v 1.44 2015/09/14 20:06:58 schwarze Exp $
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.\"
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.\" Copyright (C) Lucent Technologies 1997
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.\" All Rights Reserved
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.\"
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.\" Permission to use, copy, modify, and distribute this software and
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.\" its documentation for any purpose and without fee is hereby
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.\" granted, provided that the above copyright notice appear in all
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.\" copies and that both that the copyright notice and this
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.\" permission notice and warranty disclaimer appear in supporting
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.\" documentation, and that the name Lucent Technologies or any of
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.\" its entities not be used in advertising or publicity pertaining
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.\" to distribution of the software without specific, written prior
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.\" permission.
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.\"
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.\" LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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.\" INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
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.\" IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
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.\" SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
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.\" IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
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.\" ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
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.\" THIS SOFTWARE.
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.Dd July 30, 2021
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.Dt AWK 1
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.Os
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.Sh NAME
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.Nm awk
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.Nd pattern-directed scanning and processing language
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.Sh SYNOPSIS
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.Nm awk
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.Op Fl safe
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.Op Fl version
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.Op Fl d Ns Op Ar n
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.Op Fl F Ar fs
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.Op Fl v Ar var Ns = Ns Ar value
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.Op Ar prog | Fl f Ar progfile
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.Ar
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.Sh DESCRIPTION
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.Nm
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scans each input
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.Ar file
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for lines that match any of a set of patterns specified literally in
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.Ar prog
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or in one or more files specified as
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.Fl f Ar progfile .
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With each pattern there can be an associated action that will be performed
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when a line of a
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.Ar file
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matches the pattern.
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Each line is matched against the
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pattern portion of every pattern-action statement;
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the associated action is performed for each matched pattern.
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The file name
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.Sq -
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means the standard input.
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Any
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.Ar file
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of the form
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.Ar var Ns = Ns Ar value
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is treated as an assignment, not a filename,
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and is executed at the time it would have been opened if it were a filename.
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.Pp
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|
The options are as follows:
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.Bl -tag -width "-safe "
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.It Fl d Ns Op Ar n
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Debug mode.
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|
Set debug level to
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.Ar n ,
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or 1 if
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.Ar n
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is not specified.
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A value greater than 1 causes
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.Nm
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to dump core on fatal errors.
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.It Fl F Ar fs
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Define the input field separator to be the regular expression
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.Ar fs .
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.It Fl f Ar progfile
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Read program code from the specified file
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.Ar progfile
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instead of from the command line.
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.It Fl safe
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Disable file output
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.Pf ( Ic print No > ,
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.Ic print No >> ) ,
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process creation
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.Po
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.Ar cmd | Ic getline ,
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.Ic print | ,
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.Ic system
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.Pc
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and access to the environment
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.Pf ( Va ENVIRON ;
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see the section on variables below).
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This is a first
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.Pq and not very reliable
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approximation to a
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.Dq safe
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version of
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.Nm .
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.It Fl version
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Print the version number of
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.Nm
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to standard output and exit.
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.It Fl v Ar var Ns = Ns Ar value
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Assign
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.Ar value
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to variable
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.Ar var
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before
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.Ar prog
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is executed;
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any number of
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.Fl v
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options may be present.
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.El
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.Pp
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The input is normally made up of input lines
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.Pq records
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separated by newlines, or by the value of
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.Va RS .
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If
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.Va RS
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is null, then any number of blank lines are used as the record separator,
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and newlines are used as field separators
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(in addition to the value of
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.Va FS ) .
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This is convenient when working with multi-line records.
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.Pp
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An input line is normally made up of fields separated by whitespace,
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or by the extended regular expression
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.Va FS
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as described below.
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The fields are denoted
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.Va $1 , $2 , ... ,
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while
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.Va $0
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refers to the entire line.
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If
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.Va FS
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is null, the input line is split into one field per character.
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While both gawk and mawk have the same behavior, it is unspecified in the
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.St -p1003.1-2008
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standard.
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If
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.Va FS
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is a single space, then leading and trailing blank and newline characters are
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skipped.
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Fields are delimited by one or more blank or newline characters.
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A blank character is a space or a tab.
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If
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.Va FS
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is a single character, other than space, fields are delimited by each single
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occurrence of that character.
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The
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.Va FS
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variable defaults to a single space.
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.Pp
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Normally, any number of blanks separate fields.
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In order to set the field separator to a single blank, use the
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.Fl F
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option with a value of
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.Sq [\ \&] .
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If a field separator of
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.Sq t
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is specified,
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.Nm
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treats it as if
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.Sq \et
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had been specified and uses
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.Aq TAB
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as the field separator.
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In order to use a literal
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.Sq t
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as the field separator, use the
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.Fl F
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option with a value of
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.Sq [t] .
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.Pp
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A pattern-action statement has the form
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.Pp
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.D1 Ar pattern Ic \&{ Ar action Ic \&}
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.Pp
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A missing
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.Ic \&{ Ar action Ic \&}
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means print the line;
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a missing pattern always matches.
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Pattern-action statements are separated by newlines or semicolons.
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.Pp
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Newlines are permitted after a terminating statement or following a comma
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.Pq Sq ,\& ,
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an open brace
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.Pq Sq { ,
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a logical AND
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.Pq Sq && ,
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a logical OR
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.Pq Sq || ,
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after the
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.Sq do
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or
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.Sq else
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keywords,
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or after the closing parenthesis of an
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.Sq if ,
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.Sq for ,
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or
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.Sq while
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statement.
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Additionally, a backslash
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.Pq Sq \e
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can be used to escape a newline between tokens.
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.Pp
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An action is a sequence of statements.
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A statement can be one of the following:
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.Pp
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.Bl -tag -width Ds -offset indent -compact
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.It Ic if Ar ( expression ) Ar statement Op Ic else Ar statement
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.It Ic while Ar ( expression ) Ar statement
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.It Ic for Ar ( expression ; expression ; expression ) statement
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.It Ic for Ar ( var Ic in Ar array ) statement
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.It Ic do Ar statement Ic while Ar ( expression )
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.It Ic break
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.It Ic continue
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.It Xo Ic {
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.Op Ar statement ...
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.Ic }
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.Xc
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.It Xo Ar expression
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.No # commonly
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.Ar var No = Ar expression
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.Xc
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.It Xo Ic print
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.Op Ar expression-list
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.Op > Ns Ar expression
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.Xc
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.It Xo Ic printf Ar format
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.Op Ar ... , expression-list
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.Op > Ns Ar expression
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.Xc
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.It Ic return Op Ar expression
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.It Xo Ic next
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.No # skip remaining patterns on this input line
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.Xc
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.It Xo Ic nextfile
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.No # skip rest of this file, open next, start at top
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.Xc
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.It Xo Ic delete
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.Sm off
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.Ar array Ic \&[ Ar expression Ic \&]
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.Sm on
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.No # delete an array element
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.Xc
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.It Xo Ic delete Ar array
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.No # delete all elements of array
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.Xc
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.It Xo Ic exit
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.Op Ar expression
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.No # exit immediately; status is Ar expression
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.Xc
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.El
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.Pp
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Statements are terminated by
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semicolons, newlines or right braces.
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An empty
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.Ar expression-list
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stands for
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.Ar $0 .
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String constants are quoted
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.Li \&"" ,
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with the usual C escapes recognized within
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(see
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.Xr printf 1
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for a complete list of these).
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Expressions take on string or numeric values as appropriate,
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and are built using the operators
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.Ic + \- * / % ^
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.Pq exponentiation ,
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and concatenation
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.Pq indicated by whitespace .
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The operators
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.Ic \&! ++ \-\- += \-= *= /= %= ^=
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.Ic > >= < <= == != ?\&:
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are also available in expressions.
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Variables may be scalars, array elements
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(denoted
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.Li x[i] )
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or fields.
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Variables are initialized to the null string.
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Array subscripts may be any string,
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not necessarily numeric;
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this allows for a form of associative memory.
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Multiple subscripts such as
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.Li [i,j,k]
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are permitted; the constituents are concatenated,
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separated by the value of
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.Va SUBSEP
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.Pq see the section on variables below .
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.Pp
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The
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.Ic print
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statement prints its arguments on the standard output
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(or on a file if
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.Pf > Ar file
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or
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.Pf >> Ar file
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is present or on a pipe if
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.Pf |\ \& Ar cmd
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is present), separated by the current output field separator,
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and terminated by the output record separator.
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.Ar file
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and
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.Ar cmd
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may be literal names or parenthesized expressions;
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identical string values in different statements denote
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the same open file.
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The
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.Ic printf
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statement formats its expression list according to the format
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(see
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.Xr printf 1 ) .
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.Pp
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Patterns are arbitrary Boolean combinations
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(with
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.Ic "\&! || &&" )
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of regular expressions and
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relational expressions.
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.Nm
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supports extended regular expressions
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.Pq EREs .
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See
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.Xr re_format 7
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for more information on regular expressions.
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|
Isolated regular expressions
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in a pattern apply to the entire line.
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Regular expressions may also occur in
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relational expressions, using the operators
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.Ic ~
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and
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.Ic !~ .
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.Pf / Ar re Ns /
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is a constant regular expression;
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any string (constant or variable) may be used
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as a regular expression, except in the position of an isolated regular expression
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in a pattern.
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.Pp
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A pattern may consist of two patterns separated by a comma;
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in this case, the action is performed for all lines
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from an occurrence of the first pattern
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through an occurrence of the second.
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.Pp
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A relational expression is one of the following:
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.Pp
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.Bl -tag -width Ds -offset indent -compact
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.It Ar expression matchop regular-expression
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.It Ar expression relop expression
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.It Ar expression Ic in Ar array-name
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.It Xo Ic \&( Ns
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.Ar expr , expr , \&... Ns Ic \&) in
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.Ar array-name
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.Xc
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.El
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.Pp
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where a
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.Ar relop
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is any of the six relational operators in C, and a
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.Ar matchop
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is either
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.Ic ~
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(matches)
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or
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.Ic !~
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(does not match).
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A conditional is an arithmetic expression,
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a relational expression,
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or a Boolean combination
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of these.
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.Pp
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The special patterns
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.Ic BEGIN
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and
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.Ic END
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may be used to capture control before the first input line is read
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and after the last.
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.Ic BEGIN
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and
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.Ic END
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do not combine with other patterns.
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.Pp
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Variable names with special meanings:
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.Pp
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.Bl -tag -width "FILENAME " -compact
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.It Va ARGC
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Argument count, assignable.
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.It Va ARGV
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Argument array, assignable;
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non-null members are taken as filenames.
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.It Va CONVFMT
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Conversion format when converting numbers
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(default
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.Qq Li %.6g ) .
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.It Va ENVIRON
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Array of environment variables; subscripts are names.
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.It Va FILENAME
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The name of the current input file.
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.It Va FNR
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Ordinal number of the current record in the current file.
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.It Va FS
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Regular expression used to separate fields; also settable
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by option
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.Fl F Ar fs .
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.It Va NF
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Number of fields in the current record.
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.Va $NF
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can be used to obtain the value of the last field in the current record.
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.It Va NR
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Ordinal number of the current record.
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.It Va OFMT
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Output format for numbers (default
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.Qq Li %.6g ) .
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.It Va OFS
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Output field separator (default blank).
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.It Va ORS
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Output record separator (default newline).
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.It Va RLENGTH
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The length of the string matched by the
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.Fn match
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function.
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.It Va RS
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Input record separator (default newline).
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.It Va RSTART
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The starting position of the string matched by the
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.Fn match
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function.
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.It Va SUBSEP
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Separates multiple subscripts (default 034).
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.El
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.Sh FUNCTIONS
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The awk language has a variety of built-in functions:
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arithmetic, string, input/output, general, and bit-operation.
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.Pp
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Functions may be defined (at the position of a pattern-action statement)
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|
thusly:
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.Pp
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|
.Dl function foo(a, b, c) { ...; return x }
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.Pp
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Parameters are passed by value if scalar, and by reference if array name;
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functions may be called recursively.
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Parameters are local to the function; all other variables are global.
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Thus local variables may be created by providing excess parameters in
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the function definition.
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.Ss Arithmetic Functions
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.Bl -tag -width "atan2(y, x)"
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.It Fn atan2 y x
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Return the arctangent of
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.Fa y Ns / Ns Fa x
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in radians.
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.It Fn cos x
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Return the cosine of
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.Fa x ,
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where
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.Fa x
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is in radians.
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.It Fn exp x
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Return the exponential of
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.Fa x .
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.It Fn int x
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Return
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.Fa x
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truncated to an integer value.
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.It Fn log x
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|
Return the natural logarithm of
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.Fa x .
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|
.It Fn rand
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Return a random number,
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.Fa n ,
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such that
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.Sm off
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|
.Pf 0 \*(Le Fa n No \*(Lt 1 .
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.Sm on
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.It Fn sin x
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|
Return the sine of
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.Fa x ,
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where
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.Fa x
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is in radians.
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.It Fn sqrt x
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Return the square root of
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.Fa x .
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.It Fn srand expr
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Sets seed for
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.Fn rand
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to
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.Fa expr
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and returns the previous seed.
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|
If
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.Fa expr
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is omitted, the time of day is used instead.
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.El
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.Ss String Functions
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.Bl -tag -width "split(s, a, fs)"
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.It Fn gsub r t s
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|
The same as
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.Fn sub
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|
except that all occurrences of the regular expression are replaced.
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|
.Fn gsub
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returns the number of replacements.
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.It Fn index s t
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|
The position in
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.Fa s
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where the string
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.Fa t
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occurs, or 0 if it does not.
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.It Fn length s
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|
The length of
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.Fa s
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taken as a string,
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or of
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.Va $0
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|
if no argument is given.
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|
.It Fn match s r
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The position in
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.Fa s
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where the regular expression
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.Fa r
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occurs, or 0 if it does not.
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|
The variable
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.Va RSTART
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|
is set to the starting position of the matched string
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|
.Pq which is the same as the returned value
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or zero if no match is found.
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|
The variable
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|
.Va RLENGTH
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|
is set to the length of the matched string,
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or \-1 if no match is found.
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.It Fn split s a fs
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Splits the string
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.Fa s
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into array elements
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.Va a[1] , a[2] , ... , a[n]
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and returns
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.Va n .
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|
The separation is done with the regular expression
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.Ar fs
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or with the field separator
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.Va FS
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if
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.Ar fs
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is not given.
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|
An empty string as field separator splits the string
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into one array element per character.
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|
.It Fn sprintf fmt expr ...
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|
The string resulting from formatting
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.Fa expr , ...
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|
according to the
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.Xr printf 1
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format
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.Fa fmt .
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|
.It Fn sub r t s
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|
Substitutes
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.Fa t
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|
for the first occurrence of the regular expression
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.Fa r
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in the string
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.Fa s .
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|
If
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.Fa s
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is not given,
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|
.Va $0
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is used.
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|
An ampersand
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|
.Pq Sq &
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in
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.Fa t
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|
is replaced in string
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.Fa s
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with regular expression
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.Fa r .
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|
A literal ampersand can be specified by preceding it with two backslashes
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|
.Pq Sq \e\e .
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|
A literal backslash can be specified by preceding it with another backslash
|
|
.Pq Sq \e\e .
|
|
.Fn sub
|
|
returns the number of replacements.
|
|
.It Fn substr s m n
|
|
Return at most the
|
|
.Fa n Ns -character
|
|
substring of
|
|
.Fa s
|
|
that begins at position
|
|
.Fa m
|
|
counted from 1.
|
|
If
|
|
.Fa n
|
|
is omitted, or if
|
|
.Fa n
|
|
specifies more characters than are left in the string,
|
|
the length of the substring is limited by the length of
|
|
.Fa s .
|
|
.It Fn tolower str
|
|
Returns a copy of
|
|
.Fa str
|
|
with all upper-case characters translated to their
|
|
corresponding lower-case equivalents.
|
|
.It Fn toupper str
|
|
Returns a copy of
|
|
.Fa str
|
|
with all lower-case characters translated to their
|
|
corresponding upper-case equivalents.
|
|
.El
|
|
.Ss Input/Output and General Functions
|
|
.Bl -tag -width "getline [var] < file"
|
|
.It Fn close expr
|
|
Closes the file or pipe
|
|
.Fa expr .
|
|
.Fa expr
|
|
should match the string that was used to open the file or pipe.
|
|
.It Ar cmd | Ic getline Op Va var
|
|
Read a record of input from a stream piped from the output of
|
|
.Ar cmd .
|
|
If
|
|
.Va var
|
|
is omitted, the variables
|
|
.Va $0
|
|
and
|
|
.Va NF
|
|
are set.
|
|
Otherwise
|
|
.Va var
|
|
is set.
|
|
If the stream is not open, it is opened.
|
|
As long as the stream remains open, subsequent calls
|
|
will read subsequent records from the stream.
|
|
The stream remains open until explicitly closed with a call to
|
|
.Fn close .
|
|
.Ic getline
|
|
returns 1 for a successful input, 0 for end of file, and \-1 for an error.
|
|
.It Fn fflush [expr]
|
|
Flushes any buffered output for the file or pipe
|
|
.Fa expr ,
|
|
or all open files or pipes if
|
|
.Fa expr
|
|
is omitted.
|
|
.Fa expr
|
|
should match the string that was used to open the file or pipe.
|
|
.It Ic getline
|
|
Sets
|
|
.Va $0
|
|
to the next input record from the current input file.
|
|
This form of
|
|
.Ic getline
|
|
sets the variables
|
|
.Va NF ,
|
|
.Va NR ,
|
|
and
|
|
.Va FNR .
|
|
.Ic getline
|
|
returns 1 for a successful input, 0 for end of file, and \-1 for an error.
|
|
.It Ic getline Va var
|
|
Sets
|
|
.Va $0
|
|
to variable
|
|
.Va var .
|
|
This form of
|
|
.Ic getline
|
|
sets the variables
|
|
.Va NR
|
|
and
|
|
.Va FNR .
|
|
.Ic getline
|
|
returns 1 for a successful input, 0 for end of file, and \-1 for an error.
|
|
.It Xo
|
|
.Ic getline Op Va var
|
|
.Pf \ \&< Ar file
|
|
.Xc
|
|
Sets
|
|
.Va $0
|
|
to the next record from
|
|
.Ar file .
|
|
If
|
|
.Va var
|
|
is omitted, the variables
|
|
.Va $0
|
|
and
|
|
.Va NF
|
|
are set.
|
|
Otherwise
|
|
.Va var
|
|
is set.
|
|
If
|
|
.Ar file
|
|
is not open, it is opened.
|
|
As long as the stream remains open, subsequent calls will read subsequent
|
|
records from
|
|
.Ar file .
|
|
.Ar file
|
|
remains open until explicitly closed with a call to
|
|
.Fn close .
|
|
.It Fn system cmd
|
|
Executes
|
|
.Fa cmd
|
|
and returns its exit status.
|
|
.El
|
|
.Ss Bit-Operation Functions
|
|
.Bl -tag -width "lshift(a, b)"
|
|
.It Fn compl x
|
|
Returns the bitwise complement of integer argument x.
|
|
.It Fn and v1 v2 ...
|
|
Performs a bitwise AND on all arguments provided, as integers.
|
|
There must be at least two values.
|
|
.It Fn or v1 v2 ...
|
|
Performs a bitwise OR on all arguments provided, as integers.
|
|
There must be at least two values.
|
|
.It Fn xor v1 v2 ...
|
|
Performs a bitwise Exclusive-OR on all arguments provided, as integers.
|
|
There must be at least two values.
|
|
.It Fn lshift x n
|
|
Returns integer argument x shifted by n bits to the left.
|
|
.It Fn rshift x n
|
|
Returns integer argument x shifted by n bits to the right.
|
|
.El
|
|
.Sh EXIT STATUS
|
|
.Ex -std awk
|
|
.Pp
|
|
But note that the
|
|
.Ic exit
|
|
expression can modify the exit status.
|
|
.Sh EXAMPLES
|
|
Print lines longer than 72 characters:
|
|
.Pp
|
|
.Dl length($0) > 72
|
|
.Pp
|
|
Print first two fields in opposite order:
|
|
.Pp
|
|
.Dl { print $2, $1 }
|
|
.Pp
|
|
Same, with input fields separated by comma and/or blanks and tabs:
|
|
.Bd -literal -offset indent
|
|
BEGIN { FS = ",[ \et]*|[ \et]+" }
|
|
{ print $2, $1 }
|
|
.Ed
|
|
.Pp
|
|
Add up first column, print sum and average:
|
|
.Bd -literal -offset indent
|
|
{ s += $1 }
|
|
END { print "sum is", s, " average is", s/NR }
|
|
.Ed
|
|
.Pp
|
|
Print all lines between start/stop pairs:
|
|
.Pp
|
|
.Dl /start/, /stop/
|
|
.Pp
|
|
Simulate echo(1):
|
|
.Bd -literal -offset indent
|
|
BEGIN { # Simulate echo(1)
|
|
for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
|
|
printf "\en"
|
|
exit }
|
|
.Ed
|
|
.Pp
|
|
Print an error message to standard error:
|
|
.Bd -literal -offset indent
|
|
{ print "error!" > "/dev/stderr" }
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr cut 1 ,
|
|
.Xr lex 1 ,
|
|
.Xr printf 1 ,
|
|
.Xr sed 1 ,
|
|
.Xr re_format 7
|
|
.Rs
|
|
.%A A. V. Aho
|
|
.%A B. W. Kernighan
|
|
.%A P. J. Weinberger
|
|
.%T The AWK Programming Language
|
|
.%I Addison-Wesley
|
|
.%D 1988
|
|
.%O ISBN 0-201-07981-X
|
|
.Re
|
|
.Sh STANDARDS
|
|
The
|
|
.Nm
|
|
utility is compliant with the
|
|
.St -p1003.1-2008
|
|
specification,
|
|
except
|
|
.Nm
|
|
does not support {n,m} pattern matching.
|
|
.Pp
|
|
The flags
|
|
.Fl d ,
|
|
.Fl safe ,
|
|
and
|
|
.Fl version
|
|
as well as the commands
|
|
.Cm fflush , compl , and , or ,
|
|
.Cm xor , lshift , rshift ,
|
|
are extensions to that specification.
|
|
.Sh HISTORY
|
|
An
|
|
.Nm
|
|
utility appeared in
|
|
.At v7 .
|
|
.Sh BUGS
|
|
There are no explicit conversions between numbers and strings.
|
|
To force an expression to be treated as a number add 0 to it;
|
|
to force it to be treated as a string concatenate
|
|
.Li \&""
|
|
to it.
|
|
.Pp
|
|
The scope rules for variables in functions are a botch;
|
|
the syntax is worse.
|
|
.Sh DEPRECATED BEHAVIOR
|
|
One True Awk has accpeted
|
|
.Fl F Ar t
|
|
to mean the same as
|
|
.Fl F Ar <TAB>
|
|
to make it easier to specify tabs as the separator character.
|
|
Upstream One True Awk has deprecated this wart in the name of better
|
|
compatibility with other awk implementations like gawk and mawk.
|
|
.Pp
|
|
Historically,
|
|
.Nm
|
|
did not accept
|
|
.Dq 0x
|
|
as a hex string.
|
|
However, since One True Awk used strtod to convert strings to floats, and since
|
|
.Dq 0x12
|
|
is a valid hexadecimal representation of a floating point number,
|
|
On
|
|
.Fx ,
|
|
.Nm
|
|
has accepted this notation as an extension since One True Awk was imported in
|
|
.Fx 5.0 .
|
|
Upstream One True Awk has restored the historical behavior for better
|
|
compatibility between the different awk implementations.
|
|
Both gawk and mawk already behave similarly.
|
|
Starting with
|
|
.Fx 14.0
|
|
.Nm
|
|
will no longer accept this extension.
|
|
.Pp
|
|
The
|
|
.Fx
|
|
.Nm
|
|
sets the locale for many years to match the environment it was running in.
|
|
This lead to pattern ranges, like
|
|
.Dq "[A-Z]"
|
|
sometimes matching lower case characters in some locales.
|
|
This misbehavior was never in upstream One True Awk and has been removed as a
|
|
bug in
|
|
.Fx 12.3 ,
|
|
.Fx 13.1 ,
|
|
and
|
|
.Fx 14.0 .
|