expr
exprarg1 operator arg2
[operator arg3
...
]
Evaluates arguments as expressions and prints the result. Strings can be compared and searched. Arguments and operators must be separated by spaces. In most cases, an argument is an integer, typed literally or represented by a shell variable. There are three types of operators: arithmetic, relational, and logical. Exit status for expr is 0 (expression is nonzero and nonnull), 1 (expression is 0 or null), or 2 (expression is invalid).
expr is typically used in shell scripts to perform simple mathematics, such as addition or subtraction. It is made obsolete in the Korn shell by that program's builtin arithmetic capabilities.
Use the following operators to produce mathematical expressions whose results are printed:
+
Add arg2
to arg1
.

Subtract arg2
from arg1
.
*
Multiply the arguments.
/
Divide arg1
by arg2
.
%
Take the remainder when arg1
is divided by arg2
.
Addition and subtraction are evaluated last, unless they are grouped inside parentheses. The symbols *
, (
, and )
have meaning to the shell, so they must be escaped (preceded by a backslash or enclosed in single or double quotes).
Use relational operators
to compare two arguments. Arguments can also be words, in which case comparisons assume a < z
and A < Z
. If the comparison statement is true, the result is 1; if false, the result is 0. Symbols <
and >
must be escaped.
=
Are the arguments equal?
!=
Are the arguments different?
>
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