1.\" $NetBSD: expr.1,v 1.8 1995/03/21 09:05:37 cgd Exp $ 2.\" 3.\" -*- nroff -*- 4.\" 5.\" Copyright (c) 1993 Winning Strategies, Inc. 6.\" All rights reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by Winning Strategies, Inc. 19.\" 4. The name of the author may not be used to endorse or promote products 20.\" derived from this software without specific prior written permission 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32.\" 33.Dd July 3, 1993 34.Dt EXPR 1 35.Os 36.Sh NAME 37.Nm expr 38.Nd evaluate expression 39.Sh SYNOPSIS 40.Nm expr 41.Ar expression 42.Sh DESCRIPTION 43The 44.Nm expr 45utility evaluates 46.Ar expression 47and writes the result on standard output. 48.Pp 49All operators are separate arguments to the 50.Nm expr 51utility. 52Characters special to the command interpreter must be escaped. 53.Pp 54Operators are listed below in order of increasing precedence. 55Operators with equal precedence are grouped within { } symbols. 56.Bl -tag -width indent 57.It Ar expr1 Li | Ar expr2 58Returns the evaluation of 59.Ar expr1 60if it is neither an empty string nor zero; 61otherwise, returns the evaluation of 62.Ar expr2 . 63.It Ar expr1 Li & Ar expr2 64Returns the evaluation of 65.Ar expr1 66if neither expression evaluates to an empty string or zero; 67otherwise, returns zero. 68.It Ar expr1 Li "{=, >, >=, <, <=, !=}" Ar expr2 69Returns the results of integer comparison if both arguments are integers; 70otherwise, returns the results of string comparison using the locale-specific 71collation sequence. 72The result of each comparison is 1 if the specified relation is true, 73or 0 if the relation is false. 74.It Ar expr1 Li "{+, -}" Ar expr2 75Returns the results of addition or subtraction of integer-valued arguments. 76.It Ar expr1 Li "{*, /, %}" Ar expr2 77Returns the results of multiplication, integer division, or remainder of integer-valued arguments. 78.It Ar expr1 Li : Ar expr2 79The 80.Dq \: 81operator matches 82.Ar expr1 83against 84.Ar expr2 , 85which must be a regular expression. The regular expression is anchored 86to the beginning of the string with an implicit 87.Dq ^ . 88.Pp 89If the match succeeds and the pattern contains at least one regular 90expression subexpression 91.Dq "\e(...\e)" , 92the string corresponding to 93.Dq "\e1" 94is returned; 95otherwise the matching operator returns the number of characters matched. 96If the match fails and the pattern contains a regular expression subexpression 97the null string is returned; 98otherwise 0. 99.El 100.Pp 101Parentheses are used for grouping in the usual manner. 102.Sh EXAMPLES 103.Bl -enum 104.It 105The following example adds one to the variable a. 106.Dl a=`expr $a + 1` 107.It 108The following example returns the filename portion of a pathname stored 109in variable a. The // characters act to eliminate ambiguity with the 110division operator. 111.Dl expr "//$a" Li : '.*/\e(.*\e)' 112.It 113The following example returns the number of characters in variable a. 114.Dl expr $a Li : '.*' 115.El 116.Sh DIAGNOSTICS 117The 118.Nm expr 119utility exits with one of the following values: 120.Bl -tag -width Ds -compact 121.It 0 122the expression is neither an empty string nor 0. 123.It 1 124the expression is an empty string or 0. 125.It 2 126the expression is invalid. 127.El 128.Sh STANDARDS 129The 130.Nm expr 131utility conforms to 132.St -p1003.2 . 133