A shell function to simplify using docker (vagrant-like experience)

vm.sh

# Add to ~/.profile or ~/.bashrc, etc
# Use it like:
# vm add ubuntu # or vm add ubuntu custom/ubuntu
# vm sh ubuntu
# <ctrl-d> to detach from shell
# vm sh ubuntu # returns to the same shell
# vm stop ubuntu && vm rm ubuntu
vm() {
	case $1 in
	ls) docker ps -a ;;
	stop) shift; docker stop "$1" >/dev/null ;;
	update) shift; docker pull "$1" ;;
	rm)
		shift
		printf "remove vm %s?" "$1" >&2; read
		docker rm "$1" >/dev/null ;;
	add)
		shift
		if docker container inspect "$1" >/dev/null 2>&1; then
			echo vm "$1" already exists >&2; return 1
		fi
		if ! docker image inspect "${2-$1}" >/dev/null 2>&1; then
			docker pull "${2-$1}"
		fi
		docker create -it --name "$1" "${2-$1}" /bin/bash >/dev/null ;;
	sh)
		shift
		docker start "$1" >/dev/null &&
		if [ $# -gt 1 ]; then (
			t=$([ -t 0 ] && echo t || :); n=$1; shift
			exec docker exec -i$t "$n" /bin/bash "$@"
		) else
			docker attach --detach-keys="ctrl-d" "$1"
		fi ;;
	*)
		printf "usage: vm ls\n%s\n" \
			"$(printf "       vm %s\n" \
				"rm name" \
				"stop name" \
				"sh name [arg ...]" \
				"update image" \
				"add name [image]")" >&2
		return 1
	esac
}