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136 lines
4.4 KiB
Groff
136 lines
4.4 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1993 Winning Strategies, Inc.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Winning Strategies, Inc.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $Id: expr.1,v 1.7 1998/05/13 07:43:56 charnier Exp $
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.\"
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.Dd July 3, 1993
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.Dt EXPR 1
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.Os
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.Sh NAME
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.Nm expr
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.Nd evaluate expression
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.Sh SYNOPSIS
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.Nm expr
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.Ar expression
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.Sh DESCRIPTION
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The
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.Nm
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utility evaluates
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.Ar expression
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and writes the result on standard output.
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.Pp
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All operators are separate arguments to the
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.Nm
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utility.
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Characters special to the command interpreter must be escaped.
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.Pp
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Operators are listed below in order of increasing precedence.
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Operators with equal precedence are grouped within { } symbols.
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.Bl -tag -width indent
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.It Ar expr1 Li | Ar expr2
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Return the evaluation of
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.Ar expr1
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if it is neither an empty string nor zero;
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otherwise, returns the evaluation of
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.Ar expr2 .
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.It Ar expr1 Li & Ar expr2
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Return the evaluation of
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.Ar expr1
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if neither expression evaluates to an empty string or zero;
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otherwise, returns zero.
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.It Ar expr1 Li "{=, >, >=, <, <=, !=}" Ar expr2
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Return the results of integer comparison if both arguments are integers;
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otherwise, returns the results of string comparison using the locale-specific
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collation sequence.
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The result of each comparison is 1 if the specified relation is true,
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or 0 if the relation is false.
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.It Ar expr1 Li "{+, -}" Ar expr2
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Return the results of addition or subtraction of integer-valued arguments.
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.It Ar expr1 Li "{*, /, %}" Ar expr2
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Return the results of multiplication, integer division, or remainder of integer-valued arguments.
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.It Ar expr1 Li : Ar expr2
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The
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.Dq \:
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operator matches
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.Ar expr1
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against
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.Ar expr2 ,
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which must be a regular expression. The regular expression is anchored
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to the beginning of the string with an implicit
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.Dq ^ .
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.Pp
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If the match succeeds and the pattern contains at least one regular
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expression subexpression
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.Dq "\e(...\e)" ,
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the string corresponding to
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.Dq "\e1"
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is returned;
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otherwise the matching operator returns the number of characters matched.
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If the match fails and the pattern contains a regular expression subexpression
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the null string is returned;
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otherwise 0.
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.El
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.Pp
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Parentheses are used for grouping in the usual manner.
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.Sh EXAMPLES
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.Bl -enum
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.It
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The following example adds one to the variable a.
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.Dl a=`expr $a + 1`
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.It
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The following example returns the filename portion of a pathname stored
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in variable a. The // characters act to eliminate ambiguity with the
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division operator.
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.Dl expr "//$a" Li : '.*/\e(.*\e)'
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.It
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The following example returns the number of characters in variable a.
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.Dl expr $a Li : '.*'
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.El
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.Sh DIAGNOSTICS
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The
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.Nm
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utility exits with one of the following values:
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.Bl -tag -width indent -compact
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.It 0
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the expression is neither an empty string nor 0.
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.It 1
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the expression is an empty string or 0.
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.It 2
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the expression is invalid.
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.El
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.Sh SEE ALSO
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.Xr sh 1 ,
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.Xr test 1
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.Sh STANDARDS
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The
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.Nm
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utility conforms to
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.St -p1003.2 .
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