How to use a case statement in Zsh

A shell script often needs to turn one short input into a defined action without scattering string tests across the file. A Zsh case statement keeps those choices together and stops at the first pattern that matches.

Each branch begins with a pattern followed by ) and ends with ;;. Zsh accepts a parenthesized pattern such as (prod|production), while the | separator lets either word select the same branch.

The target router keeps the selected URL in one variable and reserves exit status 2 for invalid input. A syntax check catches an unfinished branch before execution, a recognized alias prints its assigned URL, and the catch-all branch provides fail-capable proof for an unsupported target.

1. Create deploy-target.zsh with its interpreter, strict options, and first-argument input.

   deploy-target.zsh

   #!/usr/bin/env zsh
   setopt ERR_EXIT NO_UNSET
    
   target=${1:-}

   The :- form leaves target empty when no first argument was supplied, and NO_UNSET still catches other accidental reads of undefined parameters.

2. Add the development and staging branches after the target assignment.

   case $target in
       (dev|development)
           url=https://dev.example.com
           ;;
       (stage|staging)
           url=https://staging.example.com
           ;;

   The opening parenthesis is valid Zsh case syntax. Each | pattern sends two accepted names to one assignment.

3. Add the production branch after the staging branch.

       (prod|production)
           url=https://www.example.com
           ;;

4. Close the case block with missing-target and catch-all guards.

       ("")
           print -u2 -- "missing target"
           exit 2
           ;;
       (*)
           print -u2 -- "unknown target: $target"
           exit 2
           ;;
   esac

   A leading * branch matches every target and prevents later specific branches from running.

5. Append the selected target and URL output after esac.

   print -r -- "target=$target"
   print -r -- "url=$url"

6. Check deploy-target.zsh for Zsh syntax errors.

   $ zsh -n deploy-target.zsh

   No output means Zsh parsed the completed case statement without finding a syntax error.

7. Run the shared prod|production branch with its short alias.

   $ zsh deploy-target.zsh prod
   target=prod
   url=https://www.example.com

8. Run an unsupported target to exercise the catch-all branch.

   $ zsh deploy-target.zsh sandbox
   unknown target: sandbox

9. Print the catch-all command's exit status without running another command first.

   $ printf 'exit=%s\n' "$?"
   exit=2

   A status of 2 distinguishes rejected input from a recognized branch, which returns 0. The shell replaces $? after any later command.