Math in bash itself

Bash itself is able to do simple integer arithmetic. There are at least three different ways to accomplish this in bash.

Using let

You can use the let command to do simple bash arithmetic:

$ let x=1
 $ echo $x
 1
 $ let x=$x+1
 $ echo $x
2

Basic arithmetic

You can do addition, subtraction, multiplication (be sure to escape the * operator with \*) and integer division:

expr 1 + 2
3
expr 3 \* 10
30

The numbers must be separated by spaces.

Double-parentheses

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