761 lines
16 KiB
Groff
761 lines
16 KiB
Groff
.\" $NetBSD: awk.1,v 1.17 2008/05/26 02:07:25 dholland 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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.\"
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.Dd May 25, 2008
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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
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.Op Fl F Ar fs
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.Op Fl v Ar var=value
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.Op Fl safe
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.Op Fl d Ns Op Ar N
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.Op Ar prog | Fl f Ar filename
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.Ar
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.Nm
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.Fl V
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.Sh DESCRIPTION
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.Nm
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is the Bell Labs' implementation of the AWK programming language as
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described in the
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.Em The AWK Programming Language
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by
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A. V. Aho, B. W. Kernighan, and P. J. Weinberger.
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.Pp
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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
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specified as
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.Fl f Ar filename .
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With each pattern
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there can be an associated action that will be performed
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when a line of a
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.I 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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.Ar -
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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=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 indent
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.It Fl d Ns Op Ar N
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Set debug level to specified number
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.Ar N .
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If the number is omitted, debug level is set to 1.
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.It Fl f Ar filename
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Read the AWK program source from specified file
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.Ar filename ,
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instead of the first command line argument.
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Multiple
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.Fl f
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options may be specified.
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.It Fl F Ar fs
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Set the input field separator
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.Va FS
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to the regular expression
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.Ar fs .
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.It Fl mr Ar NNN , Fl mf Ar NNN
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Obsolete, no longer needed options.
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Set limit on maximum record or
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fields number.
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.It Fl safe
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Potentially unsafe functions such as
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.Fn system
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make the program abort (with a warning message).
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.It Fl v Ar var Ns = Ns Ar value
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Assign the value
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.Ar value
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to the variable
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.Va 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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.It Fl V
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Print
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.Nm
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version on standard output and exit.
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.El
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.Pp
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An input line is normally made up of fields separated by white space,
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or by regular expression
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.Va FS .
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The fields are denoted
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.Va $1 ,
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.Va $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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.Pp
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A pattern-action statement has the form
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.sp
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.Dl pattern \&{ action \&}
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.sp
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A missing \&{ action \&}
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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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An action is a sequence of statements.
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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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.Va $0 .
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String constants are quoted \&\f(CW"\ "\fR,
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with the usual C escapes recognized within.
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Expressions take on string or numeric values as appropriate,
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and are built using the
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.Sx Operators
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(see next subsection).
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Variables may be scalars, array elements
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(denoted
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.Va 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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.Va [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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.Ss Operators
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.Nm
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operators, in order of decreasing precedence, are:
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.Pp
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.Bl -tag -width ident -compact
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.It Ic (...)
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Grouping
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.It Ic $
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Field reference
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.It Ic ++ --
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Increment and decrement, can be used either as postfix or prefix.
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.It Ic ^
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Exponentiation (the
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.Ic **
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form is also supported, and
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.Ic **=
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for the assignment operator).
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.It + - \&!
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Unary plus, unary minus and logical negation.
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.It * / %
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Multiplication, division and modulus.
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.It + -
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Addition and subtraction.
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.It Ar space
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String concatenation.
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.It Ic \*[Lt] \*[Gt]
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.It Ic \*[Le] \*[Ge]
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.It Ic != ==
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Regular relational operators
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.It Ic ~ !~
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Regular expression match and not match
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.It Ic in
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Array membership
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.It Ic "\*[Am]\*[Am]"
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Logical AND
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.It Ic "||"
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Logical OR
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.It Ic ?:
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C conditional expression.
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This is used as
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.Ar expr1 Ic ? Ar expr2 Ic : Ar expr3 No .
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If
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.Ar expr1
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is true, the result value is
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.Ar expr2 ,
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otherwise it is
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.Ar expr3 .
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Only one of
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.Ar expr2
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and
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.Ar expr3
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is evaluated.
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.It Ic = += -=
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.It Ic *= /= %= ^=
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Assignment and Operator-Assignment
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.El
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.Ss Control Statements
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The control statements are as follows:
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.Pp
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.Bl -hang -offset indent -width indent -compact
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.It Xo
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.Ic if \&( Ar expression Ic \&) Ar statement
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.Bq Ic else Ar statement
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.Xc
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.It Ic while( Ar expression Ic \&) Ar statement
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.It Xo
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.Ic for( Ar expression Ic \&; Ar expression Ic \&;
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.Ar expression Ic \&)
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.Ar statement
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.Xc
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.It Xo
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.Ic for( Va var Ic in Ar array
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.Ic \&)
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.Ar statement
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.Xc
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.It Xo
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.Ic do Ar statement
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.Ic while( Ar expression Ic \&)
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.Xc
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.It Ic break
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.It Ic continue
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.It Ic delete Va array Bq Ar expression
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.It Ic delete Va array
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.It Ic exit Bq Ar expression
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.Ar expression
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.It Ic return Bq Ar expression
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.It Ic { Ar [ statement ... ] Ic }
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.El
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.Ss I/O Statements
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The input/output statements are as follows:
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.Pp
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.Bl -tag -width indent
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.It Fn close expr
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Closes the file or pipe
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.Ar expr .
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Returns zero on success; otherwise nonzero.
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.It Fn fflush expr
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Flushes any buffered output for the file or pipe
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.Ar expr .
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Returns zero on success; otherwise nonzero.
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.It Ic getline Bq Va var
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Set
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.Va var
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(or
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.Va $0 if
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.Va var
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is not specified)
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to the next input record from the current input file.
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.Ic getline
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returns 1 for a successful input,
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0 for end of file, and \-1 for an error.
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.It Xo
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.Ic getline
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.Bq Va var
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.Ic \*[Lt]
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.Ar file
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.Xc
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Set
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.Va var
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(or
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.Va $0 if
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.Va var
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is not specified)
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to the next input record from the specified file
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.Ar file .
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.It Ar expr Ic \&| getline
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Pipes the output of
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.Ar expr
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into
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.Ic getline ;
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each call of
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.Ic getline
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returns the next line of output from
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.Ar expr .
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.It Ic next
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Skip remaining patterns on this input line.
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.It Ic nextfile
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Skip rest of this file, open next, start at top.
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.It Xo
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.Ic print
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.Bq Ar expr-list
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.Bq Ic \*[Gt] Ar file
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.Xc
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The
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.Ic print
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statement prints its arguments on the standard output (or to a file
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if
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.Ic \*[Gt] file
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or to a pipe if
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.Ic | Ar expr
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is present),
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separated by the current output field separator
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.Va OFS ,
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and terminated by the
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output record separator
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.Va ORS .
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Both
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.Ar file
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and
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.Ar expr
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may be literal names or parenthesized expressions; identical string values in
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different statements denote the same open file.
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.It Xo
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.Ic printf
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.Ar format
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.Bq Ic , Ar expr-list
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.Bq Ic \*[Gt] Ar file
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.Xc
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Format and print its expression list according to
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.Ar format .
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See
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.Xr printf 3
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for list of supported formats and their meaning.
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.El
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.Ss Mathematical and Numeric Functions
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AWK has the following mathematical and numerical functions built-in:
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.Pp
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.Bl -tag -width indent
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.It Fn atan2 x y
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Returns the arctangent of
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.Ar x Ic / Ar y
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in radians.
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See also
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.Xr atan2 3 .
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.It Fn cos expr
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Computes the cosine of
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.Ar expr ,
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measured in radians.
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See also
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.Xr cos 3 .
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.It Fn exp expr
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Computes the exponential value of the given argument
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.Ar expr .
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See also
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.Xr exp 3 .
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.It Fn int expr
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Truncates
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.Ar expr
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to integer.
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.It Fn log expr
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Computes the value of the natural logarithm of argument
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.Ar expr .
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See also
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.Xr log 3 .
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.It Fn rand
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Returns random number between 0 and 1.
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.It Fn sin expr
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Computes the sine of
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.Ar expr ,
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measured in radians.
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See also
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.Xr sin 3 .
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.It Fn sqrt expr
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Computes the non-negative square root of
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.Ar expr .
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See also
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.Xr sqrt 3 .
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.It Fn srand [expr]
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Sets seed for random number generator (
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.Fn rand )
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and returns the previous seed.
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.El
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.Ss String Functions
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AWK has the following string functions built-in:
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.Pp
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.Bl -tag -width indent
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.It Fn gensub r s h [t]
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Search the target string
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.Ar t
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for matches of the regular expression
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.Ar r .
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If
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.Ar h
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is a string beginning with
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.Ic g
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or
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.Ic G ,
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then replace all matches of
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.Ar r
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with
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.Ar s .
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Otherwise,
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.Ar h
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is a number indicating which match of
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.Ar r
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to replace.
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If no
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.Ar t
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is supplied,
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.Va $0
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is used instead.
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.\"Within the replacement text
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.\".Ar s ,
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.\"the sequence
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.\".Ar \en ,
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.\"where
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.\".Ar n
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.\"is a digit from 1 to 9, may be used to indicate just the text that
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.\"matched the
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.\".Ar n Ap th
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.\"parenthesized subexpression.
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.\"The sequence
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.\".Ic \e0
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.\"represents the entire text, as does the character
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.\".Ic & .
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Unlike
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.Fn sub
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and
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.Fn gsub ,
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the modified string is returned as the result of the function,
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and the original target is
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.Em not
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changed.
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Note that the
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.Ar \en
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sequences within replacement string
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.Ar s
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supported by GNU
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.Nm
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are
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.Em not
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supported at this moment.
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.It Fn gsub r t "[s]"
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same as
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.Fn sub
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except that all occurrences of the regular expression
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are replaced;
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.Fn sub
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and
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.Fn gsub
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return the number of replacements.
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.It Fn index s t
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the position in
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.Ar s
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where the string
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.Ar t
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occurs, or 0 if it does not.
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.It Fn length "[string]"
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the length of its argument
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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.
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.It Fn match s r
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the position in
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.Ar s
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where the regular expression
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.Ar r
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occurs, or 0 if it does not.
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The variables
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.Va RSTART
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and
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.Va RLENGTH
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are set to the position and length of the matched string.
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.It Fn split s a "[fs]"
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splits the string
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.Ar s
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into array elements
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.Va a[1] ,
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.Va a[2] ,
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\&...,
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.Va 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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Returns the string resulting from formatting
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.Ar expr
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according to the
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.Xr printf 3
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format
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.Ar fmt .
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.It Fn sub r t "[s]"
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substitutes
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.Ar t
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for the first occurrence of the regular expression
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.Ar r
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in the string
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.Ar s .
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If
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.Ar s
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is not given,
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.Va $0
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is used.
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.It Fn substr s m [n]
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Returns the at most
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.Ar n Ns No -character
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substring of
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.Ar s
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starting at position
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.Ar m ,
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counted from 1.
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If
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.Ar n
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is omitted, the rest of
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.Ar s
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is returned.
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.It Fn tolower str
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returns a copy of
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.Ar str
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with all upper-case characters translated to their
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corresponding lower-case equivalents.
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.It Fn toupper str
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returns a copy of
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.Ar str
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with all lower-case characters translated to their
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corresponding upper-case equivalents.
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.El
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.Ss Time Functions
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This
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.Nm
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provides the following two functions for obtaining time
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stamps and formatting them:
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.Bl -tag -width indent
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.It Fn systime
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Returns the value of time in seconds since the start of
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.Tn Unix
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Epoch (Midnight, January 1, 1970, Coordinated Universal Time).
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See also
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.Xr time 3 .
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.It Fn strftime "[format [, timestamp]]"
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Formats the time
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.Ar timestamp
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according to the string
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.Ar format .
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.Ar timestamp
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should be in same form as value returned by
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.Fn systime .
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If
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.Ar timestamp
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is missing, current time is used.
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If
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.Ar format
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is missing, a default format equivalent to the output of
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.Xr date 1
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would be used.
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See the specification of ANSI C
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.Xr strftime 3
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for the format conversions which are supported.
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.El
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.Ss Other built-in functions
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.Bl -tag -width indent
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.It Fn system cmd
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executes
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.Ar cmd
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and returns its exit status
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.El
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.Ss Patterns
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|
Patterns are arbitrary Boolean combinations
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|
(with
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.Ic "! || \*[Am]\*[Am]" )
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|
of regular expressions and
|
|
relational expressions.
|
|
Regular expressions are as in
|
|
.Xr egrep 1 .
|
|
Isolated regular expressions
|
|
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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|
.Ic / re /
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|
is a constant regular expression;
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|
any string (constant or variable) may be used
|
|
as a regular expression, except in the position of an isolated regular expression
|
|
in a pattern.
|
|
.Pp
|
|
A pattern may consist of two patterns separated by a comma;
|
|
in this case, the action is performed for all lines
|
|
from an occurrence of the first pattern
|
|
though an occurrence of the second.
|
|
.Pp
|
|
A relational expression is one of the following:
|
|
.Bl -tag -offset indent -width indent -compact
|
|
.It Ar expression matchop regular-expression
|
|
.It Ar expression relop expression
|
|
.It Ar expression Ic in Ar array-name
|
|
.It ( Ar expr , expr,\&... Ic ") in" Ar array-name
|
|
.El
|
|
.Pp
|
|
where a
|
|
.Ar relop
|
|
is any of the six relational operators in C,
|
|
and a
|
|
.Ar matchop
|
|
is either
|
|
.Ic ~
|
|
(matches)
|
|
or
|
|
.Ic !~
|
|
(does not match).
|
|
A conditional is an arithmetic expression,
|
|
a relational expression,
|
|
or a Boolean combination
|
|
of these.
|
|
.Pp
|
|
The special patterns
|
|
.Ic BEGIN
|
|
and
|
|
.Ic END
|
|
may be used to capture control before the first input line is read
|
|
and after the last.
|
|
.Ic BEGIN
|
|
and
|
|
.Ic END
|
|
do not combine with other patterns.
|
|
.Ss Built-in Variables
|
|
Variable names with special meanings:
|
|
.Bl -hang -width FILENAMES
|
|
.It Va ARGC
|
|
argument count, assignable
|
|
.It Va ARGV
|
|
argument array, assignable;
|
|
non-null members are taken as filenames
|
|
.It Va CONVFMT
|
|
conversion format used when converting numbers
|
|
(default
|
|
.Qq %.6g )
|
|
.It Va ENVIRON
|
|
array of environment variables; subscripts are names.
|
|
.It Va FILENAME
|
|
the name of the current input file
|
|
.It Va FNR
|
|
ordinal number of the current record in the current file
|
|
.It Va FS
|
|
regular expression used to separate fields; also settable
|
|
by option
|
|
.Fl F Ar fs .
|
|
.It Va NF
|
|
number of fields in the current record
|
|
.It Va NR
|
|
ordinal number of the current record
|
|
.It Va OFMT
|
|
output format for numbers (default
|
|
.Qq "%.6g"
|
|
)
|
|
.It Va OFS
|
|
output field separator (default blank)
|
|
.It Va ORS
|
|
output record separator (default newline)
|
|
.It Va RS
|
|
input record separator (default newline)
|
|
.It Va RSTART
|
|
Position of the first character matched by
|
|
.Fn match ;
|
|
0 if not match.
|
|
.It Va RLENGTH
|
|
Length of the string matched by
|
|
.Fn match ;
|
|
-1 if no match.
|
|
.It Va SUBSEP
|
|
separates multiple subscripts (default 034)
|
|
.El
|
|
.Ss Functions
|
|
Functions may be defined (at the position of a pattern-action statement) thus:
|
|
.Bd -filled -offset indent
|
|
.Ic function foo(a, b, c) { ...; return x }
|
|
.Ed
|
|
.Pp
|
|
Parameters are passed by value if scalar and by reference if array name;
|
|
functions may be called recursively.
|
|
Parameters are local to the function; all other variables are global.
|
|
Thus local variables may be created by providing excess parameters in
|
|
the function definition.
|
|
.Sh EXAMPLES
|
|
.Bl -tag -width indent -compact
|
|
.It Ic length($0) \*[Gt] 72
|
|
Print lines longer than 72 characters.
|
|
.Pp
|
|
.It Ic { print $2, $1 }
|
|
Print first two fields in opposite order.
|
|
.Pp
|
|
.It Ic BEGIN { FS = \&",[ \et]*|[ \et]+\&" }
|
|
.It Ic "\ \ \ \ \ \ {" print \&$2, \&$1 }
|
|
Same, with input fields separated by comma and/or blanks and tabs.
|
|
.Pp
|
|
.It Ic "\ \ \ \ {" s += $1 }
|
|
.It Xo
|
|
.Ic END { print \&"sum is\&", s, \&" average is\ \&",\ s/NR\ }
|
|
.Xc
|
|
Add up first column, print sum and average.
|
|
.Pp
|
|
.It Ic /start/, /stop/
|
|
Print all lines between start/stop pairs.
|
|
.Pp
|
|
.It Ic BEGIN { # Simulate echo(1)
|
|
.It Ic "\ \ \ \ " for (i = 1; i \*[Lt] ARGC;\ i++)\ printf\ \&"%s\ \&",\ ARGV[i]
|
|
.It Ic "\ \ \ \ " printf \&"\en\&"
|
|
.It Ic "\ \ \ \ " exit }
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr egrep 1 ,
|
|
.Xr lex 1 ,
|
|
.Xr sed 1 ,
|
|
.Xr atan2 3 ,
|
|
.Xr cos 3 ,
|
|
.Xr exp 3 ,
|
|
.Xr log 3 ,
|
|
.Xr sin 3 ,
|
|
.Xr sqrt 3 ,
|
|
.Xr strftime 3 ,
|
|
.Xr time 3
|
|
.Pp
|
|
A. V. Aho, B. W. Kernighan, P. J. Weinberger,
|
|
.Em The AWK Programming Language ,
|
|
Addison-Wesley, 1988.
|
|
ISBN 0-201-07981-X
|
|
.Pp
|
|
.Em AWK Language Programming ,
|
|
Edition 1.0, published by the Free Software Foundation, 1995
|
|
.Sh HISTORY
|
|
.Nm nawk
|
|
has been the default system
|
|
.Nm
|
|
since
|
|
.Nx 2.0 ,
|
|
replacing the previously used GNU
|
|
.Nm .
|
|
.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
|
|
\&"\&" to it.
|
|
.br
|
|
The scope rules for variables in functions are a botch;
|
|
the syntax is worse.
|