Bash Case Statements - Pattern Matching Switch

Case Statements in Bash

The case statement provides pattern-matching similar to a switch statement. It is cleaner than multiple if/elif chains when matching a variable against several patterns.

Basic Syntax

case "$variable" in
  pattern1)
    commands
    ;;
  pattern2)
    commands
    ;;
  *)
    default commands
    ;;
esac

Service Control Script

#!/usr/bin/env bash
case "$1" in
  start)
    echo "Starting service..."
    ./bin/server --daemon
    ;;
  stop)
    echo "Stopping service..."
    kill $(cat /var/run/app.pid)
    ;;
  restart)
    $0 stop
    sleep 2
    $0 start
    ;;
  status)
    if [ -f /var/run/app.pid ] && kill -0 $(cat /var/run/app.pid) 2>/dev/null; then
      echo "Running (PID: $(cat /var/run/app.pid))"
    else
      echo "Stopped"
    fi
    ;;
  *)
    echo "Usage: $0 {start|stop|restart|status}"
    exit 1
    ;;
esac

Pattern Matching Features

# OR patterns
case "$input" in
  yes|y|Y)
    echo "Confirmed"
    ;;
  no|n|N)
    echo "Cancelled"
    ;;
esac

# Wildcards
case "$filename" in
  *.tar.gz|*.tgz)
    tar -xzf "$filename"
    ;;
  *.zip)
    unzip "$filename"
    ;;
  *.deb)
    dpkg -i "$filename"
    ;;
  *)
    echo "Unknown file type"
    ;;
esac

# Character ranges
case "$char" in
  [a-z]) echo "Lowercase letter" ;;
  [A-Z]) echo "Uppercase letter" ;;
  [0-9]) echo "Digit" ;;
  *)     echo "Special character" ;;
esac

Argument Parsing

while [[ $# -gt 0 ]]; do
  case "$1" in
    -h|--help)
      usage
      exit 0
      ;;
    -v|--verbose)
      VERBOSE=true
      shift
      ;;
    -o|--output)
      OUTPUT="$2"
      shift 2
      ;;
    --)
      shift
      break
      ;;
    -*)
      echo "Unknown option: $1" >&2
      exit 1
      ;;
    *)
      ARGS+=("$1")
      shift
      ;;
  esac
done