mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-14 10:09:48 +00:00
133 lines
4.4 KiB
Groff
133 lines
4.4 KiB
Groff
.\" -*- nroff -*-
|
|
.\"
|
|
.\" Copyright (c) 1993 Winning Strategies, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by Winning Strategies, Inc.
|
|
.\" 4. The name of the author may not be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $Id: expr.1,v 1.3 1994/04/24 01:18:46 jkh Exp $
|
|
.\"
|
|
.Dd July 3, 1993
|
|
.Dt EXPR 1
|
|
.Os
|
|
.Sh NAME
|
|
.Nm expr
|
|
.Nd evaluate expression
|
|
.Sh SYNOPSIS
|
|
.Nm expr
|
|
.Ar expression
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm expr
|
|
utility evaluates
|
|
.Ar expression
|
|
and writes the result on standard output.
|
|
.Pp
|
|
All operators are separate arguments to the
|
|
.Nm expr
|
|
utility.
|
|
Characters special to the command interpreter must be escaped.
|
|
.Pp
|
|
Operators are listed below in order of increasing precedence.
|
|
Operators with equal precedence are grouped within { } symbols.
|
|
.Bl -tag -width indent
|
|
.It Ar expr1 Li | Ar expr2
|
|
Returns the evaluation of
|
|
.Ar expr1
|
|
if it is neither an empty string nor zero;
|
|
otherwise, returns the evaluation of
|
|
.Ar expr2 .
|
|
.It Ar expr1 Li & Ar expr2
|
|
Returns the evaluation of
|
|
.Ar expr1
|
|
if neither expression evaluates to an empty string or zero;
|
|
otherwise, returns zero.
|
|
.It Ar expr1 Li "{=, >, >=, <, <=, !=}" Ar expr2
|
|
Returns the results of integer comparison if both arguments are integers;
|
|
otherwise, returns the results of string comparison using the locale-specific
|
|
collation sequence.
|
|
The result of each comparison is 1 if the specified relation is true,
|
|
or 0 if the relation is false.
|
|
.It Ar expr1 Li "{+, -}" Ar expr2
|
|
Returns the results of addition or subtraction of integer-valued arguments.
|
|
.It Ar expr1 Li "{*, /, %}" Ar expr2
|
|
Returns the results of multiplication, integer division, or remainder of integer-valued arguments.
|
|
.It Ar expr1 Li : Ar expr2
|
|
The
|
|
.Dq \:
|
|
operator matches
|
|
.Ar expr1
|
|
against
|
|
.Ar expr2 ,
|
|
which must be a regular expression. The regular expression is anchored
|
|
to the beginning of the string with an implicit
|
|
.Dq ^ .
|
|
.Pp
|
|
If the match succeeds and the pattern contains at least one regular
|
|
expression subexpression
|
|
.Dq "\e(...\e)" ,
|
|
the string corresponding to
|
|
.Dq "\e1"
|
|
is returned;
|
|
otherwise the matching operator returns the number of characters matched.
|
|
If the match fails and the pattern contains a regular expression subexpression
|
|
the null string is returned;
|
|
otherwise 0.
|
|
.El
|
|
.Pp
|
|
Parentheses are used for grouping in the usual manner.
|
|
.Sh EXAMPLES
|
|
.Bl -enum
|
|
.It
|
|
The following example adds one to the variable a.
|
|
.Dl a=`expr $a + 1`
|
|
.It
|
|
The following example returns the filename portion of a pathname stored
|
|
in variable a. The // characters act to eliminate ambiguity with the
|
|
division operator.
|
|
.Dl expr "//$a" Li : '.*/\e(.*\e)'
|
|
.It
|
|
The following example returns the number of characters in variable a.
|
|
.Dl expr $a Li : '.*'
|
|
.El
|
|
.Sh DIAGNOSTICS
|
|
The
|
|
.Nm expr
|
|
utility exits with one of the following values:
|
|
.Bl -tag -width Ds -compact
|
|
.It 0
|
|
the expression is neither an empty string nor 0.
|
|
.It 1
|
|
the expression is an empty string or 0.
|
|
.It 2
|
|
the expression is invalid.
|
|
.El
|
|
.Sh STANDARDS
|
|
The
|
|
.Nm expr
|
|
utility conforms to
|
|
.St -p1003.2 .
|