What does expr mean in Unix Commands?
This page is about the meanings of the acronym/abbreviation/shorthand expr in the Computing field in general and in the Unix Commands terminology in particular.
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What does expr mean?
- expr is a command line Unix utility which evaluates an expression and outputs the corresponding value. It first appeared in Unix v7 as a standalone program, and was later incorporated into the shell as a built-in command. Syntax: expr expr evaluates integer or string expressions, including pattern matching regular expressions. Most of the challenge posed in writing expressions is preventing the invoking 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 regular expression, find a set of characters in a string; in some versions: find substring, length of string for either: comparison The following is an example involving boolean expressions: This example outputs "1". This is because length "abcdef" is 6, which is not less than 5. 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. For pure arithmetic, it is often more convenient to use bc. For example: