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EXPR(1) General Commands Manual EXPR(1) NAME expr - integer and string-match expression evaluator for shell scripts 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 in order of increasing precedence, with equal precedence operators grouped. expr1 | expr2 Value is the value of expr1 if that is neither empty nor 0, otherwise the value of expr2. expr1 & expr2 Value is the value of expr1 if neither expr1 nor expr2 is empty or 0, otherwise 0. expr1 relop expr2 Relop is one of Value is 1 if the indicated comparison is true, 0 if false. The comparison is numeric if both expr are integers, otherwise lexicographic. expr1 + expr2 expr1 - expr2 Value is the sum or difference of the (integer) values of expr1 and expr2. expr1 * expr2 expr1 / expr2 expr1 % expr2 Value is the product, quotient, or remainder of the (integer) values of expr1 and expr2. expr : regexp Match the string value of expr with the regular expression regexp; regular expression syntax is the same as in ed(1), but matches are anchored at the left. On success a subexpression \(...\), if present in regexp, picks out a return value from the matched string. Otherwise, the matching operator yields the number of characters matched (0 on failure). ( expr ) Parentheses for grouping. arg Value is the string arg. EXAMPLES a=`expr $a + 1` Add 1 to shell variable a. expr $a : '.*/\(.*\)' '|' $a Same as SEE ALSO sh(1), test(1) DIAGNOSTICS Expr returns exit code 0 if the expression is neither null nor 0, 1 if the expression is null or 0, 2 for invalid expressions. EXPR(1)