Text Case Converter

#!/usr/bin/env bash
set -euo pipefail

mode="${1:-lower}"
text="${2:-AzLearn Bash Practice}"

case "$mode" in
	lower)
		printf '%s\n' "$text" | tr '[:upper:]' '[:lower:]'
		;;
	upper)
		printf '%s\n' "$text" | tr '[:lower:]' '[:upper:]'
		;;
	kebab)
		printf '%s\n' "$text" | tr '[:upper:]' '[:lower:]' | tr ' ' '-'
		;;
	*)
		printf 'Usage: %s {lower|upper|kebab} TEXT\n' "$0" >&2
		exit 1
		;;
esac