The (( Operator

Bash performs integer arithmetic in math context.

The syntax of math context resembles the C language. The idea behind it is to make Bash easier to learn for programmers who have experience with the C language. Most users of the first Unix versions knew C.

Let’s suppose we want to store a result of adding two numbers in a variable. We need to declare it using the -i attribute and assign a value in the declaration. Here is an example:

declare -i var=12+7

Run the commands discussed in this lesson in the terminal below.