Operation expression under the shell

Commonly used arithmetic operators, assuming that variable A is 10 and variable B is 20:

Operator Description Example

+ addition ' expr $a + $b ' result is 30.

- subtraction ' expr $a-$b ' result is 10.

* multiply ' expr $a \* $b ' result is 200.

/ Division ' expr $b/$a ' result is 2.

% "expr $b% $a ' result is 0.

= Assignment a= $b assigns the value of variable B to a.

= = equal. Used to compare two numbers, the same returns true. [$a = = $b] returns FALSE.

! = is not equal. Used to compare two numbers, and returns true if they are different. [$a! = $b] Returns TRUE.

NOTE: Conditional expressions are placed between square brackets and have spaces, for example: [$a = = $b] is wrong and must be written as [$a = = $b].

Operation expression under the shell