Macintosh Terminal Pocket Guide

Name

expr — stdin  stdout  - file  -- opt  --help  --version

Synopsis

expr expression

The expr command does simple math (and other expression evaluation) on the command line:

➜ expr 7 + 3
10
➜ expr '(' 7 + 3 ')' '*' 14   We quote special shell characters
140
➜ expr length ABCDEFG
7
➜ expr 15 '>' 16
0                           Meaning false

Each argument must be separated by whitespace. Notice that we had to quote or escape any characters that have special meaning to the shell. Parentheses (escaped) may be used for grouping. Operators for expr include:

Operator	Numeric operation	String operation
+	Addition
-	Subtraction
*	Multiplication
/	Integer division
%	Remainder (modulo)
<	Less than	Earlier in dictionary.
<=	Less than or equal	Earlier in dictionary, or equal.
>	Greater than	Later in dictionary.
>=	Greater than or equal	Later in dictionary, or equal.
=	Equality	Equality.
!=	Inequality	Inequality.
|	Boolean “or”	Boolean “or”.
&	Boolean “and”	Boolean “and”.
s : regexp		Does the regular expression regexp match string s?

In Boolean expressions, expr treats the number 0 and the empty string as false; any other value is true. When returning Boolean results, expr returns 0 for false and 1 for true.

expr is not very efficient, but it’s highly useful in shell scripts, described in Programming with Shell Scripts. For more complex needs, consider using a language like Perl instead.