Bash, short for "Bourne Again SHell," is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell (sh). It is widely available on various operating systems, including Linux, macOS, and Windows (via WSL - Windows Subsystem for Linux). Bash is both a command interpreter and a scripting language, making it a powerful tool for system administrators, developers, and power users.

• Definition: A shell is a user interface for accessing an operating system's services. In the context of Unix-like systems, it is a command-line interpreter that provides a command-line user interface.
• Types of Shells: There are several types of shells, including:
  • Bourne Shell (sh)
  • C Shell (csh)
  • Korn Shell (ksh)
  • Bash (Bourne Again Shell)

• Definition: A CLI is a text-based interface used to interact with software and operating systems by typing commands into a console or terminal.
• Advantages:
  • Efficient for repetitive tasks
  • Powerful scripting capabilities
  • Greater control over the operating system

• Definition: A scripting language is a programming language designed for integrating and communicating with other programming languages. Bash scripts are used to automate tasks in Unix-like operating systems.
• Features:
  • Variables and control structures (if-else, loops)
  • Functions and modularity
  • Text processing and file manipulation

Let's start with a simple example to illustrate how Bash works. We'll create a basic script that prints "Hello, World!" to the terminal.

1. Open a Terminal: Open your terminal application. On Linux and macOS, you can use the default terminal. On Windows, you can use Git Bash or WSL.

2. Create a Script File:

   • Use a text editor to create a new file named hello.sh.
   • Add the following content to the file:

   #!/bin/bash
   echo "Hello, World!"
   

3. Save and Close the File.

4. Make the Script Executable:

   • Run the following command to make the script executable:

     chmod +x hello.sh
     

5. Run the Script:

   • Execute the script by running:

     ./hello.sh
     

• #!/bin/bash: This is called a shebang. It tells the system that the script should be executed using the Bash shell.
• echo "Hello, World!": The echo command is used to print text to the terminal.

1. Create a new script file named greet.sh.
2. Write a script that prints "Welcome to Bash Programming!".
3. Make the script executable and run it.

Solution:

1. Modify the greet.sh script to include comments explaining each line of the script.

Solution:

• Forgetting the Shebang: Always include #!/bin/bash at the top of your script to ensure it runs with the correct shell.
• File Permissions: Remember to use chmod +x to make your script executable.
• Path Issues: Ensure you are in the correct directory when running your script, or provide the full path to the script.

In this lesson, we introduced Bash, a powerful Unix shell and scripting language. We covered the basics of what a shell is, the advantages of using a command-line interface, and the fundamentals of Bash scripting. We also walked through a simple example and provided exercises to reinforce the concepts. In the next lesson, we will set up your environment to start using Bash effectively.