end_of_script.sh

main() {
    local -r FUNCTION="$1"
    case "$FUNCTION" in
        function-1)
            function_1 ;;
        function-2)
            function_2 ;;
        function-2)
            function_3 ;;
        help)
            echo "here is some help" ;;
        ?*)
            echo "unknown argument '${1}'" ;;
        *)
            echo "plz specify command" ;;
    esac
}
main "$@"