Name
expr
Synopsis
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
built-in arithmetic capabilities.
Arithmetic Operators
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).
Relational operators
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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