support long options

This change extends option parsing of the debvm tools:
 * Uses posix getopts. No additional dependencies.
 * Long option are supported. The option value may be a separate
   argument or separated with =.
 * Option value may follow short option immediately, e.g. -as390x
 * Multiple short options may be combined, e.g. -gs 2222

Technical limitation:
 * Short options are parsed inside a double dash, e.g.
   -g-image=rootfs.ext4

1 files changed, 47 insertions, 19 deletions

diff --git a/debvm-run b/debvm-run
index 972eac6..c800215 100755
--- a/debvm-run
+++ b/debvm-run
@@ -8,40 +8,68 @@ IMAGE=rootfs.ext2
 SSHPORT=
 GRAPHICAL=
 
+nth_arg() {
+	shift "$1"
+	printf "%s" "$1"
+}
+
 die() {
 	echo "$*" 1>&2
 	exit 1
 }
-
 usage() {
 	die "usage: $0 [-g] [-i image] [-s sshport] [-- qemu options]"
 }
+usage_error() {
+	echo "error: $*" 1>&2
+	usage
+}
 
-while test "$#" -gt 0; do
-	case "$1" in
-		-g)
-			GRAPHICAL=1
-			shift
-		;;
-		-i)
-			test "$#" -eq 1 && usage
-			IMAGE=$2
-			shift 2
+opt_graphical() {
+	GRAPHICAL=1
+}
+opt_image() {
+	IMAGE=$1
+}
+opt_sshport() {
+	SSHPORT=$1
+}
+
+while getopts :gi:s:-: OPTCHAR; do
+	case "$OPTCHAR" in
+		g)	opt_graphical		;;
+		i)	opt_image "$OPTARG"	;;
+		s)	opt_sshport "$OPTARG"	;;
+		-)
+			case "$OPTARG" in
+				help)
+					usage
+				;;
+				graphical|image|sshport)
+					test "$OPTIND" -gt "$#" && usage_error "missing argument for --$OPTARG"
+					"opt_$OPTARG" "$(nth_arg "$OPTIND" "$@")"
+					OPTIND=$((OPTIND+1))
+				;;
+				image=*|sshport=*)
+					"opt_${OPTARG%%=*}" "${OPTARG#*=}"
+				;;
+				*)
+					usage_error "unrecognized option --$OPTARG"
+				;;
+			esac
 		;;
-		-s)
-			test "$#" -eq 1 && usage
-			SSHPORT=$2
-			shift 2
+		:)
+			usage_error "missing argument for -$OPTARG"
 		;;
-		--)
-			shift
-			break
+		'?')
+			usage_erro "unrecognized option -$OPTARG"
 		;;
 		*)
-			usage
+			die "internal error while parsing command options, please report a bug"
 		;;
 	esac
 done
+shift "$((OPTIND - 1))"
 
 test -f "$IMAGE" || die "image '$IMAGE' not found"
 test -s "$IMAGE" || die "image '$IMAGE' is empty"