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+.\" 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 withough 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.
+.\"
+.\" $Header: /b/source/CVS/src/bin/expr/expr.1,v 1.1 1993/07/20 20:16:26 jtc 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 precidence.
+Operators with equal precidence 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 comparision if both arguments are integers;
+otherwise, returns the results of lexical comparison.
+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 begining of the string with an invisible
+.Dq ^ ,
+therefore
+.Dq ^
+is not a special character.
+.Pp
+If the pattern contains at lest 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.
+.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
+.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
+is expected to be
+.St -p1003.2
+compatible.