Learning Linux Shell Scripting

Using the expr command for arithmetic

We can use the expr command for arithmetic operations. The expr command is an external command; the binary of the expr command is stored in the folder called /usr/bin/expr.

Perform an addition operation as follows:

$ expr 40 + 2
42

Perform a subtraction operation as follows:

$ expr 42 - 2
40

Perform a division operation as follows:

$ expr 40 / 10
4

Perform a modulus (getting remainder) operation as follows:

$ expr 42 % 10
2
$ expr 4 * 10
expr: syntax error

With the expr command, we cannot use * for multiplication. We need to use \* for multiplication:

$ expr "4 * 10"
4 * 10
$ expr 4 \* 10
40

We will write a simple script to add two numbers. Write the Shell script called arithmetic_01.sh as follows:

#!/bin/bash ...