let`or`

expressions

((

expressions

))

Korn shell only. Perform arithmetic as specified by one or more integer

.
*expressions*

consist of numbers, operators, and
shell variables (which don't need a preceding *expressions*`$`

).
Expressions must be quoted if they contain spaces or other special characters.
The **(( ))** form does the quoting for you.
For more information and examples,
see "Arithmetic Expressions" earlier in this section.
See also **expr** in Section 2.

Each example below adds 1 to variable **i**.

i=`expr $i + 1` let i=i+1 let "i = i + 1" (( i = i + 1 ))