Expr 3961110 221539953 2008-06-24T23:26:10Z E dog95 1544984 + link labels {{lowercase|title=expr}} '''expr''' is a [[command line interface|command line]] [[Unix]] utility which evaluates an [[expression (mathematics)|expression]] and outputs the corresponding value. Syntax: expr ''(expression)'' ''expr'' evaluates [[integer]] or [[String (computer science)|string]] expressions, including pattern matching [[regular expression]]s. Most of the challenge posed in writing expressions is preventing the command line shell from acting on characters intended for ''expr'' to process. The operators available * for integers: addition, subtraction, multiplication, division and modulus * for strings: find substring, find regular expression, find a set of characters in a string, length of string * for either: comparison (equal, not equal, less than, etc.) Also, [[boolean]] expressions involving ''and'' and ''or'', such as expr length "abcdef" "<" 5 "|" 15 - 4 ">" 8 outputs "1". This is because length "abcdef" is 6, which is not less than 5 (so the left side of the | returns zero). But 15 minus 4 is 11 and is greater than 8, so the right side is true, which makes the ''or'' true, so 1 is the result. The program exit status is zero for this example. == External links == *[http://www.linuxmanpages.com/man1/expr.1.php The program's manpage] *[http://www.gnu.org/software/coreutils/manual/html_node/expr-invocation.html#expr-invocation expr invocation in GNU coreutils manual] {{Unix commands}} {{unix-stub}} [[Category:Unix software]] [[Category:GNU project software]] [[fr:Expr]] [[pl:Expr (Unix)]] [[ru:Expr]]