This is a custom way that I parse args in bash scripts. I consider it the most terse and readable form.

parse_args.sh

#! /usr/bin/env bash
first=""
second=""
third_flag=""

function usage() {
    echo "$0 args"
    echo ""
    echo "required arguments:"
    echo "  --first    first argument"
    echo "  --second   second argument"
}

while [[ $# -gt 0 ]];do case $1 in
    --first) first="$2"; shift;;
    --second) second="$2"; shift ;;
    --third) third_flag="1";;
    --help) usage; exit 0 ;;
esac; shift; done

if [[ -z "$first" ]] || [[ -z "$second" ]]; then
    echo "missing required arguments"
    usage
    exit 1
fi

echo "third_flag=${third_flag}";

Its not exactly the best. But I hate all the other ways of doing it. If you have more than a few parameters.. you probably should be using python.