Please don't actually use this lol

Demo

Try it out:
bash_argparse.sh --output somestring --quiet
bash_argparse.sh -o somestring -q

A little explanation

It works almost the same way as argparse from Python. You do a little
ArgumentParser parser
to create the namespace, and a sprinkle of
add_argument parser output short="-o" long="--output" action="store"
add_argument parser quiet short="-q" long="--quiet" action="store_true"
and finally a
parse_args parser args "$@"
and you have a CLI. :P