Control Flow and LogicLesson 2.3

Bash case statement for multi-branch logic

case syntax, pattern matching, wildcard patterns, | alternation in case, ;; vs ;& vs ;;& terminators, case vs if-elif chain, argument parsing with case

case: Cleaner Multi-Branch Logic

Use case instead of long if-elif chains when matching a variable against known values. It supports glob patterns, not just exact strings.

#!/usr/bin/env bash
env="$1"

case "$env" in
  production | prod)
    echo "Deploying to PRODUCTION"
    ;;
  staging | stage)
    echo "Deploying to STAGING"
    ;;
  dev | development)
    echo "Deploying to DEV"
    ;;
  *)
    echo "Unknown environment: $env" >&2
    exit 1
    ;;
esac

Pattern Matching in case

filename="report.csv"

case "$filename" in
  *.csv)
    echo "Parsing CSV"
    ;;
  *.json | *.jsonl)
    echo "Parsing JSON"
    ;;
  *.log)
    echo "Reading log"
    ;;
  *)
    echo "Unsupported format" >&2
    exit 1
    ;;
esac

Parsing CLI Arguments

while [[ $# -gt 0 ]]; do
  case "$1" in
    --output|-o)
      output_dir="$2"
      shift 2
      ;;
    --verbose|-v)
      verbose=true
      shift
      ;;
    *)
      echo "Unknown flag: $1" >&2
      exit 1
      ;;
  esac
done

The *) catch-all at the end of a case block is your safety net — always include it to handle unexpected inputs explicitly.