Case Statement

Implement menu driven scripts using case statement. Pattern matching in bash. Replace multiple if conditions. Professional script design.

What is a Case Statement?

A case statement allows you to execute different blocks of code based on the value of a variable.

It is often used as an alternative to long if-elif-else chains.

Why Use Case Statement?

Readable

Cleaner and easier to read than multiple if-else conditions.

Efficient

Simplifies decision-making logic.

Pattern Matching

Supports pattern-based matching.

Case Statement Syntax

case syntax

syntax

case $variable in
  pattern1)
    commands
    ;;
  pattern2)
    commands
    ;;
  *)
    default commands
    ;;
esac

Case Statement Examples

1. Basic Case Statement

Simple case statement to match a single value.

terminal — bash

case

read -p "Enter a number (1-3): " num
 
case $num in
  1)
    echo "You selected One"
    ;;
  2)
    echo "You selected Two"
    ;;
  3)
    echo "You selected Three"
    ;;
  *)
    echo "Invalid option"
    ;;
esac

2. Menu Driven Program

A real-world example using case for menu selection.

terminal — bash

case

echo "1. Start"
echo "2. Stop"
echo "3. Restart"
 
read -p "Choose an option: " choice
 
case $choice in
  1)
    echo "Service Started"
    ;;
  2)
    echo "Service Stopped"
    ;;
  3)
    echo "Service Restarted"
    ;;
  *)
    echo "Invalid Option"
    ;;
esac

3. Pattern Matching in Case

Case statement can match patterns.

terminal — bash

case

read -p "Enter a character: " ch
 
case $ch in
  [a-z])
    echo "Lowercase letter"
    ;;
  [A-Z])
    echo "Uppercase letter"
    ;;
  [0-9])
    echo "Digit"
    ;;
  *)
    echo "Special character"
    ;;
esac

Best Practices

Recommended Usage

Always include a default (*) case.
Use clear and readable patterns.
Avoid overly complex case blocks.
Use case for menus and user choices.

Practice Task – Case Statement

Create a menu-driven calculator.
Build a menu to start/stop a service.
Use case to check file types.

Next lesson: Functions in Shell Scripting