.TH EXPR 1 .SH NAME expr \- evaluate arguments as an expression .SH SYNOPSIS .B expr arg .B .\|.\|. .SH DESCRIPTION The arguments are taken as an expression. After evaluation, the result is written on the standard output. Each token of the expression is a separate argument. .PP The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence operators grouped. .TP .I expr | expr yields the first .I expr if it is neither null nor `0', otherwise yields the second .I expr. .TP .I expr & expr yields the first .I expr if neither .I expr is null or `0', otherwise yields `0'. .TP .I expr relop expr where .I relop is one of < = >, yields `1' if the indicated comparison is true, `0' if false. The comparison is numeric if both .I expr are integers, otherwise lexicographic. .TP .IR expr " + " expr .br .IR expr " - " expr .br addition or subtraction of the arguments. .TP .IR expr " * " expr .br .IR expr " / " expr .br .IR expr " % " expr .br multiplication, division, or remainder of the arguments. .TP .IR expr " : " expr The matching operator compares the string first argument with the regular expression second argument; regular expression syntax is the same as that of .IR ed (1). The \fB\\(\|.\|.\|.\|\\)\fP pattern symbols can be used to select a portion of the first argument. Otherwise, the matching operator yields the number of characters matched (`0' on failure). .TP .RI ( " expr " ) parentheses for grouping. .PP Examples: .PP To add 1 to the Shell variable .IR a : .IP a=\`expr $a + 1\` .PP To find the filename part (least significant part) of the pathname stored in variable .I a, which may or may not contain `/': .IP expr $a : \'.*/\e(\^.*\e)\' \'\^|\' $a .LP Note the quoted Shell metacharacters. .SH "SEE ALSO" ed(1), sh(1), test(1) .SH DIAGNOSTICS .I Expr returns the following exit codes: .PP 0 if the expression is neither null nor `0', .br 1 if the expression is null or `0', .br 2 for invalid expressions.
