Introduction to Shell Scripting

Learn the basics of shell scripting, including how to create and run simple scripts.

Introduction

Shell scripting allows you to automate tasks on your Raspberry Pi by writing scripts—collections of commands executed in sequence. This lesson introduces you to the basics of shell scripting, including how to create and run simple scripts.

Learning Objectives

• Understand what a shell script is and its uses.
• Create a simple shell script.
• Run and test your shell script.

What is a Shell Script?

A shell script is a text file containing a sequence of commands that the shell (command interpreter) can execute. Shell scripts can automate repetitive tasks, manage system configurations, and much more.

Creating a Simple Shell Script

echo is a command that prints text to the terminal.

  echo "Hello, World!"

This will simply print “Hello, World!” to the terminal.

You can also redirect the text to a file by using the > operator:

  echo "Hello, World!" > hello.sh

This will create a file named hello.sh that contains the text “Hello, World!”.

How do we know the contents of the file? For that, we can use the cat command.

What is the cat Command?

cat (catalog) is a command that displays the contents of a file:

cat hello.sh

How to Edit a File

echo and cat only works if you want to add a single line of text, or show the contents of a file. If you want to add multiple lines of text or edit an existing file you can use a text editor like nano.

To create a shell script, you can use the nano text editor. For example, to create a script that prints “Hello, World!”:

1. Open nano and create a new file:

     nano hello.sh
   

   Add the following content to the file:

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

   Save and exit nano (use Ctrl + O to save and Ctrl + X to exit).

Running Your Shell Script

To run your script, you need to make it executable and then execute it:

Make the script executable:

  chmod +x hello.sh

This will give the script permission to run as an executable.

Run the script:

  ./hello.sh

You should see “Hello, World!” printed in the terminal.

Vim

If you prefer using vim as a text editor, you can create a shell script using the following steps:

1. Open vim and create a new file:

     vim hello.sh
   

2. Press i to enter insert mode and add the following content to the file:

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

3. Press Esc to exit insert mode, then type :wq and press Enter to save and exit.

What does Vim stand for

Vim stands for Vi IMproved.

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Explanation

Vi: Vim is an enhanced version of the older text editor called vi, which stands for “visual.” Vi was one of the earliest text editors in the Unix operating system and became widely used due to its efficiency and powerful editing capabilities.

IMproved: Vim stands for “Vi IMproved” because it includes many enhancements and additional features that were not present in the original vi editor. These improvements include features like syntax highlighting, multi-level undo, support for plugins, and a more extensive command set, making it a much more powerful and flexible tool than the original vi.

vim retains compatibility with vi while offering these additional features, which is why it’s often considered a superset of vi. Despite its steep learning curve, Vim is highly regarded for its speed, efficiency, and the extensive control it gives users over text editing.

Summary

In this lesson, you learned what a shell script is and how to create and run a simple shell script. Shell scripting is a powerful tool for automating tasks and managing your Raspberry Pi more efficiently.

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