Learning Linux Shell Scripting

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 ...