Linux Shell Scripting (Day 05): Advanced Linux Shell Scripting for DevOps Engineers with User Management 🚀

Welcome to Day 05 of Linux Shell Scripting for DevOps Engineers!
This section covers advanced scripting concepts with real-world examples that are essential in the DevOps world. Scripts are written in a simple and easy-to-understand way.

What You'll Learn Today :-

• How to use loops (for, while).

• Writing .sh (shell) scripts properly.

• Using if/else conditions.

• Creating users with shell scripts.

🔁 for Loop in Shell :-

Used when you know how many times you want to run a command.

for i in 1 2 3 4 5
do
  echo "Welcome $i times"
done

➡️ Output:

Welcome 1 times
Welcome 2 times
...
...
Welcome 5 times

🔄 while Loop :-

Used when the number of iterations is unknown, runs while a condition is true.

count=1
while [ $count -le 5 ]
do
  echo "Count is $count"
  ((count++))
done

✅ if/else Statement :-

Used to make decisions in scripts.

num=10
if [ $num -gt 5 ]; then
  echo "Number is greater than 5"
else
  echo "Number is 5 or less"
fi

📂 Writing a .sh File :-

1. Create a script file:

    vim hello.sh
   

2. Add the shebang line at the top:

    #!/bin/bash
    echo "Hello from script!"
   

3. Make it executable:

    chmod +x hello .sh
   

4. Run the Script :

    ./hello.sh
   

👤 Create a New User with Shell Script

A basic user-creation script (needs root access):

#!/bin/bash

read -p "Enter username to create: " username
sudo useradd $username

if [ $? -eq 0 ]; then
  echo "User $username created successfully ✅"
else
  echo "Failed to create user ❌"
fi