#!/bin/bash

umount_one() {
	mounts=( $(gawk -v p="${root%/}" '$2 ~ "^"p { print $2 }' /proc/mounts | tac) )

	if ! ${toplevel} && [[ ${#mounts[@]} -gt 0 ]] ; then
		if [[ ${mounts[-1]} == "${root%/}" ]] ; then
			unset "mounts[-1]"
		fi
	fi

	if [[ ${#mounts[@]} -eq 0 ]] ; then
		if ! ${quiet} ; then
			echo "No mounts found for ${root}:"
			mount
		fi
		return
	fi

	if ! ${quiet} ; then
		echo "Unmounting: "
		printf '\t%s\n' "${mounts[@]}"
	fi

	if ${prompt} ; then
		printf "OK? [y/N] "
		read v
	else
		v=y
	fi
	flags=()
	${quiet} || flags+=( -v )
	[[ ${v} == "y" ]] && sudo umount "${flags[@]}" "${mounts[@]}"
}

main() {
	if [[ -z $1 ]] ; then
		echo "Usage: $0 <root>"
		exit 1
	fi

	prompt=true
	toplevel=true
	quiet=false
	while [[ $# -gt 0 ]] ; do
		case $1 in
		-y) prompt=false;;
		-s) toplevel=false;;
		-q) quiet=true;;
		*) break;;
		esac
		shift
	done

	while [[ $# -gt 0 ]] ; do
		root=$1
		shift
		umount_one "${root}"
	done
}
main "$@"