1.\" $OpenBSD: expr.1,v 1.10 2000/10/18 06:55:08 aaron Exp $ 2.\" $NetBSD: expr.1,v 1.9 1995/04/28 23:27:13 jtc Exp $ 3.\" 4.\" Written by J.T. Conklin <jtc@netbsd.org>. 5.\" Public domain. 6.\" 7.Dd July 3, 1993 8.Dt EXPR 1 9.Os 10.Sh NAME 11.Nm expr 12.Nd evaluate expression 13.Sh SYNOPSIS 14.Nm expr 15.Ar expression 16.Sh DESCRIPTION 17The 18.Nm 19utility evaluates 20.Ar expression 21and writes the result on standard output. 22All operators are separate arguments to the 23.Nm 24utility. 25Characters special to the command interpreter must be escaped. 26.Pp 27Operators are listed below in order of increasing precedence. 28Operators with equal precedence are grouped within { } symbols. 29.Bl -tag -width indent 30.It Ar expr1 Li | Ar expr2 31Returns the evaluation of 32.Ar expr1 33if it is neither an empty string nor zero; 34otherwise, returns the evaluation of 35.Ar expr2 . 36.It Ar expr1 Li & Ar expr2 37Returns the evaluation of 38.Ar expr1 39if neither expression evaluates to an empty string or zero; 40otherwise, returns zero. 41.It Ar expr1 Li "{=, >, >=, <, <=, !=}" Ar expr2 42Returns the results of integer comparison if both arguments are integers; 43otherwise, returns the results of string comparison using the locale-specific 44collation sequence. 45The result of each comparison is 1 if the specified relation is true, 46or 0 if the relation is false. 47.It Ar expr1 Li "{+, -}" Ar expr2 48Returns the results of addition or subtraction of integer-valued arguments. 49.It Ar expr1 Li "{*, /, %}" Ar expr2 50Returns the results of multiplication, integer division, or remainder of integer-valued arguments. 51.It Ar expr1 Li : Ar expr2 52The 53.Ql \&: 54operator matches 55.Ar expr1 56against 57.Ar expr2 , 58which must be a regular expression. 59The regular expression is anchored 60to the beginning of the string with an implicit 61.Ql ^ . 62.Pp 63If the match succeeds and the pattern contains at least one regular 64expression subexpression 65.Dq "\e(...\e)" , 66the string corresponding to 67.Dq "\e1" 68is returned; 69otherwise, the matching operator returns the number of characters matched. 70If the match fails and the pattern contains a regular expression subexpression 71the null string is returned; 72otherwise, returns 0. 73.El 74.Pp 75Parentheses are used for grouping in the usual manner. 76.Sh EXAMPLES 77.Cm a=`expr $a + 1` 78.Pp 79Add 1 to the variable 80.Va a . 81.Pp 82.Cm expr "//$a" \&: '.*/\e(.*\e)' 83.Pp 84Return the filename portion of a pathname stored 85in variable 86.Va a . 87The 88.Ql // 89characters act to eliminate ambiguity with the division operator. 90.Pp 91.Cm expr $a \&: '.*' 92.Pp 93Return the number of characters in variable 94.Va a . 95.Sh DIAGNOSTICS 96The 97.Nm 98utility exits with one of the following values: 99.Pp 100.Bl -tag -width Ds -compact 101.It 0 102The expression is neither an empty string nor 0. 103.It 1 104The expression is an empty string or 0. 105.It 2 106The expression is invalid. 107.It >2 108An error occurred (such as memory allocation failure). 109.El 110.Sh SEE ALSO 111.Xr test 1 112.Sh STANDARDS 113The 114.Nm 115utility conforms to 116.St -p1003.2 . 117