Expr

expr is a shell command that evaluates an expression and outputs the result. It evaluates integer or string expressions, including pattern matching regular expressions. Comparison operators (equal, not equal, less than, etc.) apply to both integer and string values. Integer-specific operations include addition, subtraction, multiplication, division and modulus. String-specific operators include: matching a regular expression (, or the colon syntax for an arbitrary string "str" and regular expression "reg") finding a set of characters in a string () finding a substring () finding the length