How to Use Case Statement in Bash: Syntax and Examples

In bash, use the case statement to match a variable against multiple patterns and execute code based on the match. It starts with case VARIABLE in, followed by patterns and commands, and ends with esac. This helps simplify complex if-else chains.

Syntax

The case statement checks a variable against multiple patterns. Each pattern ends with ) and is followed by commands to run if matched. Use ;; to end each pattern block. The statement ends with esac (case spelled backwards).

• case VARIABLE in: Start the case statement with the variable to test.
• pattern): Define a pattern to match the variable.
• commands: Commands to run if the pattern matches.
• ;;: Ends the commands for that pattern.
• esac: Ends the entire case statement.

bash

case VARIABLE in
  pattern1)
    commands
    ;;
  pattern2)
    commands
    ;;
  *)
    default_commands
    ;;
esac

Example

This example shows how to use a case statement to print a message based on the day of the week stored in a variable.

bash

#!/bin/bash
DAY="Tuesday"
case $DAY in
  Monday)
    echo "Start of the work week.";;
  Tuesday|Wednesday|Thursday)
    echo "Midweek days.";;
  Friday)
    echo "Almost weekend!";;
  Saturday|Sunday)
    echo "Weekend!";;
  *)
    echo "Not a valid day.";;
esac

Output

Midweek days.

Common Pitfalls

Common mistakes when using case in bash include:

• Forgetting the ;; at the end of each pattern block causes syntax errors.
• Not quoting variables can cause unexpected word splitting or globbing.
• Using incorrect pattern syntax, like missing ) after patterns.
• Not including a default * pattern to catch unmatched cases.

bash

# Wrong: Missing ;;
case $var in
  yes)
    echo "Yes"  # Missing ;; here
  no)
    echo "No";;
esac

# Right:
case $var in
  yes)
    echo "Yes";;
  no)
    echo "No";;
esac

Quick Reference

Element	Description
case VARIABLE in	Start the case statement with the variable to test
pattern)	Pattern to match the variable
commands	Commands to run if pattern matches
;;	Ends the commands for the current pattern
*)	Default pattern if no other matches
esac	Ends the case statement

Key Takeaways

Use case to simplify multiple condition checks in bash scripts.

Always end each pattern block with ;; to avoid syntax errors.

Include a default * pattern to handle unexpected values.

Patterns can be combined with | to match multiple values.

Quote variables when necessary to prevent word splitting or globbing.