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 + 242

Perform a subtraction operation as follows:

$ expr 42 - 240

Perform a division operation as follows:

$ expr 40 / 104

Perform a modulus (getting remainder) operation as follows:

$ expr 42 % 102$ expr 4 * 10expr: syntax error

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

$ expr "4 * 10"4 * 10$ expr 4 * 1040

We will write a simple script to add two numbers. Write the shell script, 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

This is the output:

7

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

#!/bin/bash ...