Using the let command for arithmetic

We can use the bash built-in command let for performing arithmetic operations. To get more information about let, type the following:

$ help let

Output:

Let's start using the let command:

$ value=6
$ let value=value+1
$ echo $value
7
$ let "value=value+4"
$ echo $value
11
$ let "value+=1"
#above expression evaluates as value=value+1
$ echo $value
12

A summary of operators available with the let command follows:

• Operation: Operator

• Unary minus: –

• Unary plus: +

• Logical NOT:!

• Bitwise NOT (negation):~

• Multiply: *

• Divide: /

• Remainder: %

• Subtract: –

• Add:+

Prior to bash 2.x, the following operators were not available:

• Bitwise left shift: <<

• Bitwise right shift: >>

• Equal to and not equal to: ==, !=

• Comparison operators: <=,>=,<,>

• Bitwise AND: &

• Bitwise: |

• Bitwise exclusive OR: ^

• Logical AND: &&

• Logical OR: ||

• Assignment and shortcut assignment: = *=/= %= –= += >>= <<= &= |= ^=