EXPR(1) EXPR(1) NAME expr - evaluate arguments as an expression SYNOPSIS expr arg ... 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. The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence opera- tors grouped. expr | expr yields the first expr if it is neither null nor `0', otherwise yields the second expr. expr & expr yields the first expr if neither expr is null or `0', otherwise yields `0'. expr relop expr where relop is one of < <= = != >= >, yields `1' if the indicated comparison is true, `0' if false. The com- parison is numeric if both expr are integers, otherwise lexicographic. expr expr addition or subtraction of the arguments. expr expr expr multiplication, division, or remainder of the argu- ments. expr The matching operator compares the string first argu- ment with the regular expression second argument; regu- lar expression syntax is the same as that of ed(1). The \(...\) pattern symbols can be used to select a portion of the first argument. Otherwise, the matching opera- tor yields the number of characters matched (`0' on failure). ( expr ) parentheses for grouping. EXPR(1) EXPR(1) EXAMPLES a=`expr $a + 1` Add 1 to shell variable a. expr $a : '.*/(.*)' '|' $a Find the filename part (least significant part) of pathname a, which may or may not contain `/'. Note the quoted shell metacharacters. SEE ALSO sh(1), test(1) DIAGNOSTICS Expr returns the following exit codes: 0 if the expression is neither null nor `0', 1 if the expression is null or `0', 2 for invalid expressions.