How to write a shell script to add two numbers?

Adding Two Numbers in a Shell Script

Writing a shell script to add two numbers is a common task in shell programming. Shell scripts are a powerful tool for automating repetitive tasks and performing simple calculations. In this guide, we'll walk through the steps to create a shell script that adds two numbers.

Understanding Shell Scripts

A shell script is a text file containing a series of commands that the shell (the command-line interface) can execute. Shell scripts are written in a specific shell language, such as Bash (Bourne-Again SHell), which is the most widely used shell on Linux and macOS systems.

Shell scripts are useful for a variety of tasks, including:

• Automating repetitive tasks
• Performing calculations and data processing
• Interacting with the operating system
• Launching other programs or scripts

To create a shell script, you'll need a text editor and a shell installed on your system. The basic structure of a shell script is as follows:

#!/bin/bash
# This is a comment
command1
command2
command3

The first line, #!/bin/bash, is called the "shebang" and tells the system which shell to use to execute the script. The rest of the script contains the commands you want to run.

Adding Two Numbers in a Shell Script

To add two numbers in a shell script, you can use the built-in arithmetic expansion feature of the shell. Here's an example script:

#!/bin/bash

# Prompt the user to enter two numbers
echo "Enter the first number: "
read num1
echo "Enter the second number: "
read num2

# Add the two numbers
result=$((num1 + num2))

# Display the result
echo "The sum of $num1 and $num2 is $result"

Let's break down the script:

1. The script starts with the shebang #!/bin/bash, which tells the system to use the Bash shell to execute the script.
2. The script prompts the user to enter two numbers using the echo command and the read command to store the user input in the variables num1 and num2.
3. The script then performs the addition using the arithmetic expansion $((num1 + num2)) and stores the result in the variable result.
4. Finally, the script displays the result using the echo command.

To run the script, save it to a file (e.g., add_numbers.sh) and make it executable with the chmod command:

chmod +x add_numbers.sh

Then, you can run the script with:

./add_numbers.sh

The script will prompt you to enter two numbers, and it will display the sum of those numbers.

Explaining the Concept with a Mermaid Diagram

Here's a Mermaid diagram that explains the flow of the shell script:

This diagram shows the step-by-step process of the shell script, from prompting the user for input to displaying the final result.

Real-World Example: Calculating the Area of a Rectangle

Let's consider a real-world example to make the concept more relatable. Imagine you're a construction worker, and you need to calculate the area of a rectangular room to determine the amount of flooring or paint required. You can use a shell script to automate this task.

#!/bin/bash

# Prompt the user for the length and width of the room
echo "Enter the length of the room (in feet): "
read length
echo "Enter the width of the room (in feet): "
read width

# Calculate the area
area=$((length * width))

# Display the result
echo "The area of the room is $area square feet."

In this example, the script prompts the user to enter the length and width of the room, calculates the area by multiplying the two values, and then displays the result. This can be a useful tool for construction workers, interior designers, or anyone who needs to quickly calculate the area of a rectangular space.

By using a shell script to perform this calculation, you can save time and reduce the risk of errors compared to manually calculating the area. Additionally, you can easily modify the script to handle different units of measurement or perform more complex calculations if needed.

In conclusion, writing a shell script to add two numbers is a straightforward task that demonstrates the power and versatility of shell programming. By understanding the basic structure of shell scripts and the arithmetic expansion feature, you can create scripts to automate a wide range of tasks, from simple calculations to complex data processing workflows.