Introduction to Bash Scripting

Bash scripting is a core skill for Linux cybersecurity professionals. It allows you to automate tasks, manage systems, and run security tools efficiently. By writing scripts, repetitive tasks can be automated, saving time and reducing errors.

1. What is Bash?

Bash stands for Bourne Again Shell. It is a command-line interpreter that executes commands and scripts in Linux.

• Bash scripts are plain text files containing commands executed sequentially.
• Scripts can automate tasks like file management, network scanning, backups, and log analysis.

Check Bash version:

bash --version

2. Writing Simple Scripts

Creating a Script

1. Create a file with .sh extension:

nano hello.sh

2. Add the shebang at the top (tells the system which shell to use):

#!/bin/bash
echo "Hello, Linux Cybersecurity!"

3. Save and exit (Ctrl + O, Enter, Ctrl + X).
4. Make the script executable:

chmod +x hello.sh

5. Run the script:

./hello.sh

Output:

Hello, Linux Cybersecurity!

3. Variables in Bash

Variables store data that can be reused in scripts.

Assigning Variables

name="CRMNuggets"

Using Variables

echo "Welcome, $name!"

Output:

Welcome, CRMNuggets!

Read Input from User

read -p "Enter your username: " user
echo "Hello, $user!"

4. Basic Scripting Commands

Common commands used in Bash scripts:

Example: Conditional Statement

#!/bin/bash
read -p "Enter a number: " num
if [ $num -gt 10 ]; then
    echo "The number is greater than 10."
else
    echo "The number is 10 or less."
fi

Example: Loop

#!/bin/bash
for i in {1..5}
do
    echo "Iteration $i"
done

Output:

Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5

5. Automating Simple Tasks

Bash scripts can automate:

• File and directory management
• Backup creation
• Log analysis
• Network scanning
• System updates

Example: Automated Backup Script

#!/bin/bash
tar -czf backup_$(date +%F).tar.gz /home/student/Documents
echo "Backup completed successfully!"

This script creates a compressed backup of the Documents directory with a timestamp.

Cybersecurity Importance

• Automates repetitive security tasks
• Creates custom security monitoring scripts
• Performs routine system maintenance efficiently
• Supports penetration testing and auditing

Module Summary

Students should now understand:

1. What Bash is and why it’s important
2. How to create and run simple scripts
3. How to use variables and user input
4. Basic scripting commands: loops, conditionals, and commands
5. How to automate simple Linux tasks