🐚 Bash Case Statements – Use case, in, and esac for Multi-Condition Scripts

Introduction to Bash Case Statements – Simplify Multi-Condition Checks

When a script needs to evaluate multiple possible values of a variable and perform actions accordingly, case statements offer a cleaner alternative to multiple if-elif-else blocks. The Bash case command works like a switch-case construct in other programming languages and is ideal for handling menu selections, argument parsing, and input validation.

In this article, you’ll learn:

• How to write a case statement in Bash
• Syntax and structure of case, in, and esac
• Pattern matching in case blocks
• Practical use cases and script examples

Basic Syntax of case Statement

case $variable in
  pattern1)
    command1
    ;;
  pattern2)
    command2
    ;;
  *)
    default_command
    ;;
esac

Example 1: Simple Menu Using case

echo "Choose an option: start | stop | status"
read action

case $action in
  start)
    echo "Starting service..."
    ;;
  stop)
    echo "Stopping service..."
    ;;
  status)
    echo "Service status: Running"
    ;;
  *)
    echo "Invalid option"
    ;;
esac

Sample Run:

Choose an option: start | stop | status  
> start  
Starting service...

Example 2: Pattern Matching with Wildcards

read -p "Enter filename: " file

case $file in
  *.txt)
    echo "Text file"
    ;;
  *.sh)
    echo "Shell script"
    ;;
  *)
    echo "Unknown file type"
    ;;
esac

Output:

Enter filename: test.sh  
Shell script

You can match file extensions, numbers, or wildcard patterns.

Example 3: Case with Command-Line Arguments

case "$1" in
  start)
    echo "App started"
    ;;
  stop)
    echo "App stopped"
    ;;
  restart)
    echo "App restarted"
    ;;
  *)
    echo "Usage: $0 {start|stop|restart}"
    ;;
esac

Run:

./script.sh restart

Output:

App restarted

Why Use case Instead of if-elif-else?

Advanced Patterns

You can use multiple matches with |:

case $input in
  y|Y|yes|YES)
    echo "You said yes."
    ;;
  n|N|no|NO)
    echo "You said no."
    ;;
  *)
    echo "Unknown input."
    ;;
esac

Summary – Bash Case Statements

The case statement in Bash is your go-to tool for handling multiple input conditions clearly and efficiently. It’s a perfect fit for user menus, argument validation, file type checks, and automation logic.

Key Takeaways:

• Use case, in, esac to check multiple input patterns
• ;; separates each case block
• * acts as a default (catch-all)
• More readable and scalable than nested if statements

Real-world Uses:

• Parsing script parameters
• Creating interactive terminal menus
• Handling file type conditions in automation scripts

FAQ – Bash Case Statements

Can I use regex in a Bash case statement?
Not full regex, but you can use glob patterns like *.txt, [0-9]*, etc.

What does ;; mean in a case statement?
It ends the current condition block and prevents fall-through to the next one.

Is case faster than if in Bash?
Slightly more efficient in matching many conditions and much more readable for multiple options.

Can I use variables inside patterns?
Not directly. Pattern matching must use literal values or glob-style patterns, not variable substitution.

How do I add a default action in a case statement?
Use *:

*)
  echo "Default case"
  ;;