How to use a case statement in Zsh

A Zsh case statement lets a script choose one branch from a fixed set of words or shell patterns. It fits command dispatch, environment selection, and menu-style script arguments where a long chain of string comparisons would be harder to scan.

Each branch starts with a pattern ending in ) and ends with ;;. Multiple accepted words can share one branch with |, and a final * branch catches values that do not match any earlier pattern.

The example maps a target name to a URL, validates the file with zsh -n, and runs matched and unmatched inputs. Known targets print the selected URL, while empty or unknown targets print guard messages instead of a URL.

Steps to use a case statement in Zsh:

Create a script that matches the first argument against target names.

deploy-target.zsh

#!/usr/bin/env zsh
emulate -L zsh
setopt err_exit no_unset
 
target=${1:-}
 
case "$target" in
    dev|development)
        url="https://dev.example.com"
        ;;
    staging)
        url="https://staging.example.com"
        ;;
    production|prod)
        url="https://www.example.com"
        ;;
    "")
        print -u2 -- "missing target"
        exit 1
        ;;
    *)
        print -u2 -- "unknown target: $target"
        exit 1
        ;;
esac
 
print -r -- "target=$target"
print -r -- "url=$url"

The dev|development and production|prod branches accept two words each. The quoted empty-string branch handles a missing argument before the fallback * branch handles unsupported targets.

Check the script syntax before running it.
```
$ zsh -n deploy-target.zsh
```
No output from zsh -n means Zsh parsed the case block, branch endings, and esac marker without finding a syntax error.

Run a target that has one exact branch.

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

Run a target from a branch that also accepts a short alias.

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

Confirm that an unsupported target reaches the fallback branch.
```
$ zsh deploy-target.zsh sandbox
unknown target: sandbox
```
Keep the fallback * branch last. Earlier patterns are tested first, so a leading * branch would catch every value before the specific branches can run.
Confirm that a missing target reaches the empty-string branch.
```
$ zsh deploy-target.zsh
missing target
```
Remove the sample script after testing.
```
$ rm -f deploy-target.zsh
```