Calculating the sum of two integers (numbers) in a shell script is pretty simple as in other programming languages. Bash shell provides a command-line utility called `expr`

to evaluate expressions. The latest version of the Bash shell also includes the functionality to evaluate expressions directly with the shell.

In this tutorial, we will discuss a few methods to calculate the sum of the two numbers in a bash script.

## 1. Bash – Adding Two Numbers

The `expr`

is the command-line utility used for evaluating mathematical expressions. Bash shell also supports evaluating the mathematical expressions directly.

Use the following syntax to calculate the sum of two integers in a shell script:

- Using
`expr`

command with backquotes (` `):`sum=`expr $num1 + $num2``

- Use
`expr`

command enclosed with brackets and start with dollar symbol:`sum=$(expr $num1 + $num2)`

- This is
**my preferred way**to directly with the shell:`sum=$(($num1 + $num2))`

In the next few examples, we will discuss calculating the sum of numbers directly with a shell. You can also choose **expr** command to give the syntax above.

## 2. Calculate Sum in Shell Script

Bash shell also evaluates the mathematical expressions directly. You just need to write the expressions enclosed in double brackets with a dollar like `$((...))`

.

Write an example shell script to initialize two numeric variables. Then perform an addition operation on both values and store results in the third variable.

```
#!/bin/bash
# Calculate the sum of two integers with pre initialize values
# in a shell script
# Initialize two variables with number
a=10
b=20
# Calculate sum
sum=$(( $a + $b ))
# Display the result
echo "Sum is: $sum"
```

Output:

Sum is: 30

## 3. Calculate Sum with Command Line Arguments

In this second example, the shell script reads two numbers as command line parameters and performs the addition operation.

```
#!/bin/bash
# Calculate the sum via command-line arguments
# $1 and $2 refers to the first and second argument passed as command-line arguments
# Calculate sum
sum=$(( $1 + $2 ))
# Display the result
echo "Sum is: $sum"
```

Let’s execute this script is a shell

`./sum.sh 12 14`

# Executing script Sum is: 26

## 4. Calculate Sum with Run Time Input

Here is another example of a shell script, which takes input from the user at run time. Then calculate the sum of given numbers and store to a variable and show the results.

```
#!/bin/bash
# Take input from user and calculate sum.
read -p "Enter first number: " num1
read -p "Enter second number: " num2
# Calculate sum
sum=$(( $num1 + $num2 ))
# Display the result
echo "Sum is: $sum"
```

Output:

Enter first number: 12 Enter second number: 15 Sum is: 27

## Conclusion

In conclusion, we have explored different methodologies to handle a fundamental yet crucial aspect of programming—calculating the sum of two integers—in the context of Bash shell scripting. This knowledge is fundamental in the realm of shell scripting, which offers a powerful way to automate tasks, and the techniques covered here form the building blocks for more complex script-based operations.

## 4 Comments

How to add two float value using shell script

Bro use this header file at the top of your code

#!/bin/bash

code :

echo -n “enter the num1 ==> ”

read num1

echo -n “enter the num2 ==> ”

read num2

sum =$(( $num1 + $num2 ))

echo “the sum of $num1 and $num2 is ==> $sum”

i have written this code but it shows me some errors so can you help me ?

error :

enter the num1 ==> 10

enter the num2 ==> 20

sum: ‘=30’: No such file or directory

the sum of 10 and 20 is ==>

Hi Dixit,

Remove space after “sum variable”

The full script should be