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
x=5
y=2
z=`expr $x + $y`
echo $z
Test the script as follows:
$ chmod +x arithmetic_01.sh
$ ./arithmetic_01.sh

The output is here:

7

Let's write a script to perform all the basic arithmetic operations. Write the Shell script called arithmetic_02.sh...