📥 Shell Scripting for Beginners – Part 2: Reading User Input in Shell

🚀 Part 2: Making Scripts Interactive

• Using the read command for user input
• Creating scripts that listen to user responses
• Essential for real-world scripting and automation

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💡 What is the read Command?

The read command accepts user input. Think of it as your script saying — "Hey human, tell me something so I can automate it for you." 😎

read variable_name

Whatever the user types will be stored inside $variable_name.

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🎯 Example 1: Basic User Input

#!/bin/bash
echo "What is your name?"
read name
echo "Hello $name, welcome to MiddlewareBox!"

💬 Output:

What is your name?
John
Hello John, welcome to MiddlewareBox!

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⚙️ Example 2: Read with Prompt in Same Line

#!/bin/bash
read -p "Enter your environment (dev/stage/prod): " env
echo "Deploying application to $env environment..."

💬 Output:

Enter your environment (dev/stage/prod): dev
Deploying application to dev environment...

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🔐 Example 3: Hidden Input (Password)

#!/bin/bash
read -sp "Enter your Jenkins admin password: " password
echo
echo "Password received! (Not displayed for security)"

💬 Output:

Enter your Jenkins admin password: ********
Password received! (Not displayed for security)

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⏰ Example 4: Set Timeout for Input

#!/bin/bash
read -t 5 -p "Enter server name within 5 seconds: " server
echo "Server chosen: $server"

💬 Output:

Enter server name within 5 seconds: middlewarebox01
Server chosen: middlewarebox01

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📦 Example 5: Default Value if User Skips Input

#!/bin/bash
read -p "Enter build version (default: 1.0): " version
version=${version:-1.0}
echo "Deploying build version $version..."

💬 Output:

Enter build version (default: 1.0):
Deploying build version 1.0...

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💾 Example 6: Take Multiple Inputs Together

#!/bin/bash
read -p "Enter username and group: " user group
echo "Creating user: $user in group: $group"

💬 Output:

Enter username and group: devops admins
Creating user: devops in group: admins

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🧰 Example 7: Restart Tomcat with User Confirmation

#!/bin/bash
read -p "Do you want to restart Tomcat? (yes/no): " choice
if [[ "$choice" == "yes" ]]; then
  echo "Stopping Tomcat..."
  sh /opt/tomcat/bin/shutdown.sh
  sleep 3
  echo "Starting Tomcat..."
  sh /opt/tomcat/bin/startup.sh
  echo "✅ Tomcat restarted successfully!"
else
  echo "❌ Operation cancelled."
fi

💬 Output:

Do you want to restart Tomcat? (yes/no): yes
Stopping Tomcat...
Starting Tomcat...
✅ Tomcat restarted successfully!

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🧠 Example 8: Jenkins Backup Trigger

#!/bin/bash
read -p "Do you want to back up Jenkins data now? (y/n): " answer
if [[ "$answer" == "y" ]]; then
  backup_dir="/var/jenkins_home/backup"
  mkdir -p $backup_dir
  tar -czf $backup_dir/jenkins_backup_$(date +%F).tar.gz /var/jenkins_home
  echo "✅ Jenkins backup created in $backup_dir"
else
  echo "🕒 Backup skipped by user."
fi

💬 Output:

Do you want to back up Jenkins data now? (y/n): y
✅ Jenkins backup created in /var/jenkins_home/backup

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🌍 Example 9: Deployment Environment Selector

#!/bin/bash
read -p "Enter deployment environment (dev/test/prod): " env
case $env in
  dev)
    echo "🚀 Deploying to Development servers..."
    ;;
  test)
    echo "🧪 Deploying to Testing servers..."
    ;;
  prod)
    echo "⚠️ Deploying to Production environment..."
    ;;
  *)
    echo "❌ Invalid environment!"
    ;;
esac

💬 Output:

Enter deployment environment (dev/test/prod): prod
⚠️ Deploying to Production environment...

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📁 Example 10: Check and Read File Path Before Processing

#!/bin/bash
read -p "Enter the log file path: " logfile
if [[ -f "$logfile" ]]; then
  echo "Analyzing log file..."
  grep -i "error" $logfile | head -5
else
  echo "❌ File not found: $logfile"
fi

💬 Output:

Enter the log file path: /var/log/nginx/error.log
Analyzing log file...
[error] 1054#1054: *1 connect() failed (111: Connection refused)
[error] 1055#1055: *2 open() "/var/www/html/404.html" failed (2: No such file)

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🧩 Example 11: Take User Input in a CI/CD Script

#!/bin/bash
read -p "Enter Git branch to deploy: " branch
read -p "Enter version tag: " version
echo "Cloning branch '$branch'..."
git clone -b $branch https://github.com/middlewarebox/myapp.git
echo "Deploying version $version..."
echo "✅ Deployment completed!"

💬 Output:

Enter Git branch to deploy: main
Enter version tag: v2.0
Cloning branch 'main'...
✅ Deployment completed!

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🧠 Example 12: User Confirmation for Rollback

#!/bin/bash
read -p "Rollback to previous version? (yes/no): " rollback
if [[ "$rollback" == "yes" ]]; then
  echo "🔁 Rolling back..."
  echo "✅ Rollback completed successfully!"
else
  echo "👍 Staying on current version."
fi

💬 Output:

Rollback to previous version? (yes/no): yes
🔁 Rolling back...
✅ Rollback completed successfully!

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🏁 Conclusion

In DevOps and Middleware environments, interactive scripts save time and prevent mistakes.

← Previous: Part 1 – What is a Variable? Next: Part 3 – Conditional Statements →