Shell aritmetic operations on the command line

You can perform simple aritmetic operations on the Linux shell command line, without using any external program.
use the command expr
These are the aritmetic operations.

• Add
expr 1 + 2
• Substract
expr 2 - 1
• Multiply
expr 2 \* 1
• Divide
expr 2 / 1
• Reminder of a divition
expr 20 % 3

Note that for multiplication we escape the * character, with the back slash, and that the % operand gives as the reminder of a divition, also the divition is only giving as the Integer