Can you show more complex case examples?

To see the real power of case statements, we can look at examples involving pattern matching, multiple conditions, and system tasks.

Here are three complex examples:

1. The "File Organizer" (Pattern Matching)

This example uses wildcards (*) to determine what to do with different file types.

#!/bin/bash
FILE=$1

case "$FILE" in
    *.jpg | *.png | *.gif)
        echo "$FILE is an image file."
        ;;
    *.mp3 | *.wav)
        echo "$FILE is an audio file."
        ;;
    *.sh)
        echo "$FILE is a shell script."
        ;;
    *)
        echo "Unknown file type: $FILE"
        ;;
esac

Key Feature: The | (pipe) allows one block of code to handle multiple file extensions.

2. The "Smart Input" (Character Classes)

You can use case to validate the type of data entered by a user.

#!/bin/bash
read -p "Enter a single character: " DATA

case "$DATA" in
    [0-9])
        echo "You entered a digit."
        ;;
    [a-z])
        echo "You entered a lowercase letter."
        ;;
    [A-Z])
        echo "You entered an uppercase letter."
        ;;
    ?)
        echo "You entered a special symbol."
        ;;
    *)
        echo "You entered more than one character or nothing at all."
        ;;
esac

Key Feature: [a-z] and [0-9] represent ranges. The single ? matches exactly one character that isn't a letter or digit.

3. The "System Menu" (Infinite Loop + Case)

This is a standard way to build a command-line interface (CLI) for system administration.

#!/bin/bash
while true; do
  echo "--- SYSTEM MENU ---"
  echo "1. Show Disk Usage"
  echo "2. Show Uptime"
  echo "3. Exit"
  read -p "Choose an option [1-3]: " choice

  case $choice in
    1)
        df -h | head -n 5
        ;;
    2)
        uptime -p
        ;;
    3)
        echo "Goodbye!"
        exit 0
        ;;
    *)
        echo "Invalid choice, try again."
        ;;
  esac
  echo "" 
done

Key Feature: Combining case with a while true loop creates an interactive tool that keeps running until the user chooses "Exit".

Why these are better than if-elif:

• Cleaner Syntax: Handling *.jpg | *.png in an if statement would require long strings of [[ $FILE == *.jpg ]] || [[ $FILE == *.png ]].
• Scalability: You can easily add 10 more file types to Example 1 without making the code hard to read.

Which of these styles would be most useful for your own project?