Bash Case Statement

A case statement compares one value against a list of patterns and runs the code of the first match. It replaces long chains of if and elif lines and keeps menu-style scripts tidy.

A Railway Signal Analogy

A railway signal shows red, yellow, or green. The driver reads the color and picks one action: stop, slow down, or go. A case statement reads a value and picks one block of code in the same way.

              +-----------------+
              |  value: $color  |
              +--------+--------+
                       |
        +--------------+--------------+
        |              |              |
        v              v              v
     "red"          "yellow"       "green"
     Stop           Slow down        Go

Basic Syntax

case value in
  pattern1)
    commands
    ;;
  pattern2)
    commands
    ;;
  *)
    default commands
    ;;
esac

Each block ends with ;;. The word esac (case spelled backward) closes the whole statement. The * pattern catches every value that matched nothing before it.

Example: Traffic Signal

#!/bin/bash
read -p "Enter signal color: " color

case $color in
  red)
    echo "Stop the vehicle"
    ;;
  yellow)
    echo "Slow down"
    ;;
  green)
    echo "Go ahead"
    ;;
  *)
    echo "Unknown color"
    ;;
esac

Output (input: green):

Go ahead

Match Several Patterns in One Block

The pipe symbol | means "or". Use it to share one block between several values.

#!/bin/bash
read -p "Answer yes or no: " reply

case $reply in
  y|Y|yes|YES)
    echo "You agreed"
    ;;
  n|N|no|NO)
    echo "You declined"
    ;;
  *)
    echo "Please type yes or no"
    ;;
esac

Use Wildcards in Patterns

Patterns support the same wildcards as file names. The star matches any text, the question mark matches one character, and square brackets match a set.

#!/bin/bash
file=$1

case $file in
  *.txt)
    echo "Text document"
    ;;
  *.jpg|*.png)
    echo "Image file"
    ;;
  *.sh)
    echo "Shell script"
    ;;
  [0-9]*)
    echo "Name starts with a digit"
    ;;
  *)
    echo "Unknown file type"
    ;;
esac

Run ./type.sh photo.png and the screen shows Image file.

Build a Simple Menu

#!/bin/bash
echo "1) Show date"
echo "2) Show folder"
echo "3) Show user"
echo "4) Exit"
read -p "Choose an option: " choice

case $choice in
  1) date ;;
  2) pwd ;;
  3) whoami ;;
  4) echo "Goodbye" ;;
  *) echo "Invalid choice" ;;
esac

Short commands fit on one line with ;; at the end. Longer blocks work better with one command per line.

Handle Command Line Actions

Service scripts often accept words like start and stop:

#!/bin/bash
case $1 in
  start)
    echo "Starting service..."
    ;;
  stop)
    echo "Stopping service..."
    ;;
  restart)
    echo "Restarting service..."
    ;;
  *)
    echo "Usage: $0 {start|stop|restart}"
    exit 1
    ;;
esac

Case Versus If

Situation	Better Choice
One value, many fixed options	case
Number comparisons such as greater than	if
Pattern checks on file names	case
Several different conditions combined	if

Common Mistakes

• A missing ;; merges two blocks into a syntax error.
• A *) pattern placed first catches every value and blocks the others.
• Spaces inside patterns need quotation marks, such as "New York").
• Case compares text only. Use if with -gt or -lt for number ranges.

Key Takeaways

• case picks one block from a list of patterns.
• Each block ends with ;;, and the statement ends with esac.
• Use | to join several patterns and *) for the default block.
• Wildcards make file type checks short and readable.
• Menus and service scripts use case statements often.