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UNIX in a Nutshell: System V Edition

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The Bourne Shell and Korn Shell
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4.4 Arithmetic Expressions

The Korn shell's let command performs integer arithmetic. The Korn shell provides a way to substitute integer values (for use as command arguments or in variables); base conversion is also possible:

$(( expr ))

Use the value of the enclosed arithmetic expression.


Interpret integer n in numeric base B. For example, 8#100 specifies the octal equivalent of decimal 64.

4.4.1 Operators

The Korn shell uses arithmetic operators from the C programming language; they are listed below in decreasing order of precedence:


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.

*= /= %=


= += -=

<<= >>=

&= ^= |=

4.4.2 Examples

See the let command for more information and examples.

let "count=0" "i = i + 1"	Assign i and count.
let "num % 2"	Test for an even number.
(( percent >= 0 && percent <= 100 ))	Test the range of a value.

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