#!/bin/bash

provided_options=

do_has_option()
{
	echo "$1" | grep -q -- "\(^\| \)$2\(\$\| \)"
}

has_option()
{
	do_has_option "$provided_options" "$1"
}

while true
do
	case $1 in
	-*)
		if do_has_option "$allowed_options" "$1"
		then
			provided_options+=" $1"
		else
			echo "Unknown option: $1"
			usage
		fi
		shift
		;;
	*)
		break
		;;
	esac
done