case

case variable in
    pattern1)
        action1
        ;;
    pattern2 | pattern3)
        action2
        ;;
    *)
        default action
        ;;
esac

Pattern	Description
word)	Exact match. Executes when the value equals word.
pat1 | pat2)	OR condition. Executes when the value matches either pattern.
*.txt)	Wildcard pattern. Matches any string ending in .txt.
[aeiou])	Character class. Matches any one of the characters a, e, i, o, or u.
?)	Matches any single character.
*)	Default pattern that matches everything. Place it last.
;;	Terminates a pattern block (does not fall through to the next pattern).
;&	Falls through and executes the next pattern block regardless (Bash 4+).
;;&	Evaluates the next pattern and executes it if it matches (Bash 4+).

Branches execution based on a command-line argument. Use | to combine multiple values into a single OR condition.

service.sh

#!/bin/bash
action=$1

case "$action" in
    start)
        echo "Starting the service"
        ;;
    stop)
        echo "Stopping the service"
        ;;
    restart | reload)
        echo "Restarting the service"
        ;;
    status)
        echo "Checking service status"
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|reload|status}"
        exit 1
        ;;
esac

bash service.sh restart
Restarting the service

Uses wildcard patterns to determine a file type by its extension.

filetype.sh

filename="report.pdf"
case "$filename" in
    *.php | *.py | *.rb)
        echo "Script file"
        ;;
    *.txt | *.md | *.csv)
        echo "Text file"
        ;;
    *.jpg | *.png | *.gif)
        echo "Image file"
        ;;
    *.pdf)
        echo "PDF file"
        ;;
    *)
        echo "Unknown file type"
        ;;
esac

bash filetype.sh
PDF file

Uses the character class [0-9] to check a numeric range.

grade_case.sh

score=85
case $score in
    9[0-9] | 100)
        echo "A (Excellent)"
        ;;
    8[0-9])
        echo "B (Good)"
        ;;
    7[0-9])
        echo "C (Pass)"
        ;;
    *)
        echo "D (Fail)"
        ;;
esac

bash grade_case.sh
B (Good)

Case patterns use shell glob patterns (wildcards), not regular expressions. If you need regex matching, use the =~ operator with if / [[ ]].

Separating patterns with | lets you group OR conditions into a single block. Compared to if-elif chains, case is more concise and easier to read.

The default pattern *) is optional, but it is recommended to always include it to handle unexpected input gracefully.