Section 5.4. Arithmetic Expressions


5.4. 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.

Table 5-30. Syntax for arithmetic expressions

Expression

Meaning

(( expr ))

Use the value of the enclosed arithmetic expression.


5.4.1. Operators

bash uses arithmetic operators from the C programming language; the following list is in decreasing order of precedence. Use parentheses to override precedence.

Table 5-31. Arithmetic operators

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


5.4.2. 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  



MAC OS X Tiger in a Nutshell
Mac OS X Tiger in a Nutshell: A Desktop Quick Reference (In a Nutshell (OReilly))
ISBN: 0596009437
EAN: 2147483647
Year: 2003
Pages: 130

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