Shell scripting is one of the most powerful skills you can learn in Linux. It allows you to automate repetitive tasks, build simple tools, and combine commands into workflows. Whether you’re an aspiring system administrator or DevOps engineer, shell scripting is a must-have skill.

What is a Shell Script?

A shell script is simply a text file that contains Linux commands executed in sequence by a shell (like bash, zsh, or sh).

Think of it as saving a series of terminal commands into a file so you can run them all at once.

Creating Your First Script

1. Create a new file:

    nano hello.sh
   

2. Add the following content:

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

   

3. Save and exit.

4. Make it executable:

    chmod +x hello.sh
   

5. Run it:

    ./hello.sh
   

Variables in Shell Scripts

Variables let you store and reuse values.

#!/bin/bash
name="Marwan"
echo "Hello, $name!"

Output:

Hello, Marwan!

Conditional Statements

Use if statements to add logic:

#!/bin/bash
if [ -f "/etc/passwd" ]; then
    echo "File exists."
else
    echo "File does not exist."
fi

Loops

Loops let you repeat tasks automatically.

For Loop Example:

#!/bin/bash
for i in 1 2 3 4 5
do
   echo "Number: $i"
done

While Loop Example:

#!/bin/bash
count=1
while [ $count -le 5 ]
do
   echo "Count: $count"
   count=$((count + 1))
done

Functions

Functions make scripts reusable and modular.

#!/bin/bash
greet() {
   echo "Hello, $1!"
}
greet "Linux User"

Useful Commands in Scripts

• date → Print current date and time

• uptime → Show system uptime

• df -h → Disk usage

• free -m → Memory usage

• ps aux → Running processes

These can all be combined into scripts for automation.

Hands-on Labs

Here are 9 labs to practice, sorted by difficulty.

🟢 Beginner Labs (Basic Scripting Skills)

Lab 1: Greeting Script

• Ask for the user’s name (read name) and print:

    Hello, <name>! Welcome to Linux.
  

✅ Goal: Learn input, variables, and echo.

Lab 2: Simple Calculator

• Write a script that takes two numbers as input and prints their sum.
  Hint: Use read and arithmetic $(( )).
  ✅ Goal: Practice input and basic math.

Lab 3: Even or Odd Checker

• Ask for a number.

• Print whether it’s even or odd.
  Hint: Use modulus operator %.
  ✅ Goal: Practice conditionals.

🟡 Intermediate Labs (Automation & File Handling)

Lab 4: Backup a Directory

• Takes a directory as input.

• Creates a .tar.gz backup with today’s date.

• Saves it in /tmp/backups/.
  ✅ Goal: Automate backups.

Lab 5: Log File Cleaner

• Find and delete all .log files older than 7 days in /var/log/.
  Hint: Use find /var/log -name "*.log" -mtime +7 -delete.
  ✅ Goal: Automate system housekeeping.

Lab 6: User Creation Script

• Ask for a username.

• Create the user and set a default password.

• Add them to the developers group.
  ✅ Goal: Automate sysadmin tasks.

🔴 Advanced Labs (Reusable Tools & System Monitoring)

Lab 7: System Health Report

• Print:

  • Current date & time (date)

  • Uptime (uptime)

  • Disk usage (df -h)

  • Memory usage (free -m)

  • Top 5 processes (ps aux --sort=-%mem | head -n 6)
    ✅ Goal: Build a reusable admin tool.

Lab 8: Network Connectivity Checker

• Read a list of hostnames from a file.

• Loop through and ping each one.

• Print which hosts are up and which are down.
  ✅ Goal: Practice loops + conditionals with real networking.

Lab 9: Automated Service Monitor

• Check if nginx or apache2 is running.

• If not, restart it and log the event to /var/log/service_monitor.log.
  ✅ Goal: Automate monitoring & recovery.

Conclusion

With these labs, you’ll progress from simple echo scripts to building real-world automation tools. Shell scripting is a skill that grows with you: the more you practice, the more powerful your Linux workflows become.

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Practice Pack Script

Here’s the linux-shell-labs.sh file (all 9 labs with comments):

#!/bin/bash
# Linux Shell Scripting Labs
# Run: chmod +x linux-shell-labs.sh && ./linux-shell-labs.sh

######################
# Beginner Labs
######################

# Lab 1: Greeting Script
greeting_lab() {
    read -p "Enter your name: " name
    echo "Hello, $name! Welcome to Linux."
}

# Lab 2: Simple Calculator
calculator_lab() {
    read -p "Enter first number: " a
    read -p "Enter second number: " b
    echo "Sum = $((a + b))"
}

# Lab 3: Even or Odd Checker
evenodd_lab() {
    read -p "Enter a number: " num
    if (( num % 2 == 0 )); then
        echo "$num is even."
    else
        echo "$num is odd."
    fi
}

######################
# Intermediate Labs
######################

# Lab 4: Backup a Directory
backup_lab() {
    read -p "Enter directory to backup: " dir
    mkdir -p /tmp/backups
    tar -czf /tmp/backups/backup-$(date +%F).tar.gz "$dir"
    echo "Backup saved in /tmp/backups/"
}

# Lab 5: Log File Cleaner
logclean_lab() {
    find /var/log -name "*.log" -mtime +7 -exec rm -f {} \;
    echo "Old log files cleaned."
}

# Lab 6: User Creation Script
usercreate_lab() {
    read -p "Enter username: " user
    sudo useradd -m "$user"
    echo "$user:password" | sudo chpasswd
    sudo usermod -aG developers "$user"
    echo "User $user created and added to 'developers' group."
}

######################
# Advanced Labs
######################

# Lab 7: System Health Report
sysreport_lab() {
    echo "System Health Report - $(date)"
    uptime
    df -h
    free -m
    ps aux --sort=-%mem | head -n 6
}

# Lab 8: Network Connectivity Checker
netcheck_lab() {
    read -p "Enter file with hostnames: " file
    while read host; do
        if ping -c 1 -W 1 "$host" &> /dev/null; then
            echo "$host is UP"
        else
            echo "$host is DOWN"
        fi
    done < "$file"
}

# Lab 9: Automated Service Monitor
servicemon_lab() {
    service="nginx"
    if ! systemctl is-active --quiet $service; then
        echo "$(date): $service was down, restarting..." >> /var/log/service_monitor.log
        sudo systemctl restart $service
    else
        echo "$service is running."
    fi
}

######################
# Menu
######################
while true; do
    echo -e "\nChoose a Lab to Run:
    1) Greeting
    2) Calculator
    3) Even/Odd
    4) Backup Directory
    5) Log Cleaner
    6) User Creation
    7) System Report
    8) Network Check
    9) Service Monitor
    0) Exit"
    read -p "Enter choice: " choice
    case $choice in
        1) greeting_lab ;;
        2) calculator_lab ;;
        3) evenodd_lab ;;
        4) backup_lab ;;
        5) logclean_lab ;;
        6) usercreate_lab ;;
        7) sysreport_lab ;;
        8) netcheck_lab ;;
        9) servicemon_lab ;;
        0) exit ;;
        *) echo "Invalid choice" ;;
    esac
done