dirname.bash

function dirname {
	local names=() delim='\n' n x
	local VERSION=0.1

	while [[ $# -gt 0 ]]; do
		case $1 in
		-h|--help)
			echo "Usage: dirname [OPTIONS] [--] NAME ...

Removes the last non-slash component from NAME and the slashes that
follow it.  The result is then further trimmed of remaining trailing
slashes.  A resulting name that is empty evaluates to '/' or '.'
depending if the original name begins with a forward slash or not.

Options:
  -z, --zero     Use NUL as delimiter instead of a newline
  -h, --help     Show this usage info and exit
  -v, --version  Show version and exit"
			;;
		-v|--version)
			echo "${VERSION}"
			;;
		-z|--zero)
			delim='\0'
			;;
		--)
			names+=("${@:2}")
			break
			;;
		-[!-][!-]*)
			set -- "${1:0:2}" "-${1:2}" "${@:2}"
			continue
			;;
		-?*)
			echo "dirname: Unrecognized option: $1" >&2
			return 1
			;;
		*)
			names+=("$1")
			;;
		esac

		shift
	done

	if ! shopt -q extglob; then
		echo "dirname: This function requires extglob enabled." >&2
		return 1
	fi

	if [[ ${#names[@]} -eq 0 ]]; then
		echo "dirname: No name specified." >&2
		return 1
	fi

	for n in "${names[@]}"; do
		x=${n%%+([^/])*(/)} x=${x%%+(/)}

		if [[ -z $x ]]; then
			[[ $n == /* ]] && x=/ || x=.
		fi

		printf "%s${delim}" "$x"
	done

	return 0
}