Writing Your First Shell Script

1. Introduction

Shell scripting in Linux enables users to combine command-line tools into executable programs. These scripts streamline workflows, improve efficiency, and offer deeper control over system behavior.

2. What Are Shell Scripts?

A shell script is a plain-text file containing a sequence of shell commands. Bash is the most common interpreter, capable of running both interactive and scripted command sets.

3. Steps to Create a Shell Script

1. Write the Script: Use text editors like vim, gedit, or kate with syntax highlighting
2. Make It Executable: Use chmod to assign permissions
3. Place It in PATH: Store in a directory listed in the PATH environment variable

4. Creating a "Hello World" Script

Step 1: Write the Script

#!/bin/bash
# This is our first script
echo 'Hello World!'

• Shebang: Tells the system to use Bash
• Comments: Begin with #, ignored during execution
• Command: echo prints to the terminal

Step 2: Make the Script Executable

chmod 755 hello_world

755 makes the script executable for all users. Use chmod 700 for private scripts.

Step 3: Place the Script in PATH

mkdir ~/bin
mv hello_world ~/bin

If ~/bin isn’t in $PATH, add it via ~/.bashrc:

export PATH=~/bin:"$PATH"
. ~/.bashrc

5. Running the Script

With ~/bin in $PATH:

hello_world

Without $PATH integration:

./hello_world

6. Best Locations for Scripts

• Personal Use: ~/bin
• System-Wide: /usr/local/bin or /usr/local/sbin
• Avoid: /bin or /usr/bin (reserved for distributions)

7. Enhancing Script Readability

• Use long option names: ls --all --directory
• Indent long commands: Use backslash \ for line continuation

find playground \
  \( -type f -not -perm 0600 -exec chmod 0600 '{}' ';' \) \
  -or \
  \( -type d -not -perm 0700 -exec chmod 0700 '{}' ';' \)

8. Configuring Vim for Script Writing

Add to ~/.vimrc:

syntax on
set hlsearch
set tabstop=4
set autoindent

• Syntax Highlighting: Colors script elements based on structure
• Tab Width: Improves line readability
• Auto-indentation: Aligns new lines efficiently

9. Conclusion

Writing shell scripts is a foundational Linux skill for automation and productivity. By building a simple “Hello World” script and applying proper permissions and placement, users unlock the ability to create powerful tools. Techniques like formatting, indentation, and editor configuration improve script clarity, paving the way for advanced scripting.