Chapter #1: What Is a Shell Script and Why Use It?

Bash stands for "Bourne Again Shell", which is an improved version of the original Unix shell developed back in the 1970s. Bash was introduced in 1989 and quickly became the default shell for most Linux systems.

Bash is how we interact with the Linux system. In simple terms, a shell script or Bash script is a way to tell Linux what to do. Whether you're creating files, adding users, or configuring networks, shell scripts make it all faster and easier.

While you can type individual commands in the terminal, a Bash script is a collection of commands written in a file to automate tasks. It’s like writing a mini program that takes care of the work for you, saving time and effort.

What’s the Difference Between Shell, Bash, and Bash Script?

This may be confusing at first, and many beginners don't clearly understand how this works or the difference between the terms Bash, Shell, and Bash Script.

What Is Shell?

A Shell is a command-line interface that acts as a bridge between you (the user) and the Linux system. It takes your commands, passes them to the system, and returns the output.

Here’s how it works:

You open the terminal, which is an application used to write commands. When you type a command, the shell reads it, parses it, and translates it into something the kernel (the core of the Linux system) can understand. This process is called a system call. The kernel then executes the command and returns the result to your screen.

What is Bash?

Bash is just one type of shell. In fact, there are several types - like sh (Bourne Shell), csh (C Shell), zsh (Z Shell), and others. Each has its own features and syntax.

But among them, Bash is the most popular and widely used, especially in Linux environments. That’s why when we talk about writing scripts, we often say Bash Script.

What Is Shell Scripting or Bash Scripting?

Now that we understand what Bash is, the next question is: what is Shell Scripting or Bash Scripting?

Simply put, instead of typing and running individual commands one by one, you can group a series of commands in a file - this file is called a script.

When you run the script, it executes all the commands in sequence, performing a complete task automatically.

In short:

A shell script is a set of commands saved in a file that tells the Linux system what to do - step by step.

What Can We Do with Bash Scripts?

As we mentioned earlier, a Bash script is a powerful way to interact with your Linux system, which allows you to do everything from creating files to monitoring the system - all in an automated and efficient way.

Bash scripting is a vital skill for any Linux system administrator, as it simplifies daily tasks and reduces manual effort.

One of the best ways to understand the value of Bash scripting is by looking at repetitive tasks. Let’s say you have a set of commands you need to run regularly. Doing this manually each time is time-consuming and error-prone.

This is where shell scripting makes life easier; you just write those commands once inside a script, and then run the script whenever needed. It performs the entire task for you, without needing to repeat the steps manually. This process is called automation.

For example, let's say you need to create a user in the system with a certain default password, which would take some time executing commands specific to user creation in Linux.

Instead, you can put these commands into a script, and whenever you need to create a new user, you simply run the script! A new user is added.

#!/bin/bash
echo "Creating new user..."
useradd newuser
echo "User created!"

And that’s just one example. You can use Bash scripts to automate all sorts of tasks, such as backups, updates, log rotation, software installations, system cleanups, and much more.

What Is the Role of a Bash Script?

Linux itself is a command-line system, but you can use Linux without the need for a graphical user interface (GUI) application. All you need is the terminal, and you're good to go - you can install packages, create or delete files, add and remove users, all within the terminal prompt.

That is the magic of the shell: every command you run on the command line is a shell command, meaning it's the way to communicate with your system - the language that Linux understands.

Whether you are a system administrator or a developer working on Linux, you need to know shell scripting to have a way to interact with your system. Otherwise, you will struggle to use Linux, as most operations require some interaction with the shell and commands.

Bash vs. Other Programming Languages

As mentioned earlier, Bash is a system scripting language designed for tasks related to automation, file manipulation, and system administration.

In contrast, programming languages like Python, C, and Java are built for more complex applications and serve different purposes. While they can be used to write scripts that interact with the system, their primary focus is not system-level automation.

For example, you can write a Python script that interacts with the operating system just like Bash does, but Python requires additional libraries to achieve this. On the other hand, Bash communicates directly with the system without the need for third-party dependencies.

This brings us to another key point: performance. Bash is fast and lightweight because it is built into the Linux system and doesn't rely on external libraries. In contrast, other programming languages often require additional setup and dependencies to perform the same tasks.

For quick, efficient, and direct system automation, Bash is the better choice. However, for more complex application development, languages like Python or C are more suitable.

What You Will Learn in This Series

Bash is a powerful and fun scripting language to learn, but it needs the right explanation and guidance to make it simple and easy to understand.

In this series, we’ll start learning Bash from the ground up, using simple examples that gradually build toward more advanced topics like automating real-world tasks with Bash scripts.

Just follow along from start to finish, and you’ll gain the knowledge and skills needed for your Linux sysadmin journey. Every chapter is designed to build on the last, so you’ll learn everything in a logical and practical way.

No prior experience is needed. You don’t need to know Linux or shell scripting to get started. We’ll assume you’re a total beginner and guide you step by step into the world of Linux and Bash scripting.