7.4. Arithmetic Expressions
The let command performs integer arithmetic.
bash provides a way to substitute
integer values (for use as command arguments or in variables); base
conversion is also possible.
Expression
|
Meaning
|
((
expr))
|
Use the value of the enclosed arithmetic expression.
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7.4.1. Operators
bash uses arithmetic operators from
the C programming language; the following list is in decreasing order
of precedence. Use parentheses to override precedence.
Operator
|
Meaning
|
-
|
Unary minus
|
! ~
|
Logical negation; binary inversion (one's
complement)
|
* / %
|
Multiplication; division; modulus (remainder)
|
+ -
|
Addition; subtraction
|
<< >>
|
Bitwise left shift; bitwise right shift
|
<= >=
|
Less than or equal to; greater than or equal to
|
< >
|
Less than; greater than
|
= = !=
|
Equality; inequality (both evaluated left to right)
|
&
|
Bitwise AND
|
^
|
Bitwise exclusive OR
|
|
|
Bitwise OR
|
&&
|
Logical AND
|
||
|
Logical OR
|
=
|
Assign value
|
+= -=
|
Reassign after addition/subtraction
|
*= /= %=
|
Reassign after multiplication/division/remainder
|
&= ^= |=
|
Reassign after bitwise AND/XOR/OR
|
<<= >>=
|
Reassign after bitwise shift left/right
|
7.4.2. Examples
See the let built-in command for
more information and examples.
let "count=0" "i = i + 1" Assign i and count
let "num % 2"; echo $? Test for an even number
| | | 7.3. Variables | | 7.5. Command History |
Copyright © 2003 O'Reilly & Associates. All rights reserved.
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