separate system-independent parts of volume(1)

bin/volume

@@ -1,10 +1,9 @@
 #!/bin/sh
+set -e
 
 argv0="$0"
 
 # ADDING A NEW SOUND SERVER/CLIENT/WHATEVERIDK
-# `volume a` and `volume s` are the system dependent functions.
-
 # `volume a $2` must set the volume to $2, an integer value. This should be a
 # percentage, 100% being the loudest possible volume that can be output by
 # hardware without quality loss. Percentages above 100% will be allowable in
@@ -16,22 +15,18 @@ argv0="$0"
 
 VOLUME_TMP_FILE="$HOME/.volume-previous"
 
-system_determine(){
-	if [ "$(uname)" = NetBSD ]; then
-		printf "NetBSD\n"
-	elif command -v pactl >/dev/null 2>&1; then
-		printf "PulseAudio\n"
-	fi
-}
-
-unknown_system(){
-	printf "%s: Unknown system.\n" "$argv0" 1>&2
+if [ "$(uname)" = NetBSD ]; then
+	VOLUME_SYSTEM=netbsd
+elif command -v pactl >/dev/null 2>&1; then
+	VOLUME_SYSTEM=pulseaudio
+else
+	printf "%s: Unknown system.\n" "$0"
 	exit 1
-}
+fi
 
 usage(){
 	printf "\
-Usage: %b {function} (operand)\n" "$argv0"
+Usage: %b {function} (operand)\n" "$0"
 	printf "\
 Functions:
 	'+'      - shortcut to \"relative \$2\"
@@ -51,63 +46,32 @@ works the same as \"%b h\".
 	exit 1
 }
 
-# $1 becomes 'help' if previously empty
-[ -n "$1" ] \
-	&& argv1="$1" \
-	|| argv1=help
+case "$1" in
 
-case "$argv1" in
-#
-# SYSTEM DEPENDENT
-#
-a*) [ -n "$2" ] || usage
-	case "$(system_determine)" in
-	NetBSD)
-		# NetBSD 9.2 STABLE 2021-07
-		audioctl -w play.gain=$2 >/dev/null
-		;;
-	PulseAudio)
-		# pactl 15.0 compiled+linked with libpulse 15.0.0
-		pactl set-sink-volume @DEFAULT_SINK@ $2%
-		;;
-	*)	unknown_system ;;
-	esac; exit 0 ;;
++) "$0" r  "$2" ;;
+-) "$0" r -"$2" ;;
 
-s*) [ -z "$2" ] || usage
-	case "$(system_determine)" in
-	NetBSD) # hacky
-		audioctl -a \
-			| grep "play\.gain" \
-			| cut -d '=' -f 2
-		;;
-	PulseAudio)
-		# really hacky, gets the job done
-		# gets the volume % of Lchan specifically
-		pactl get-sink-volume @DEFAULT_SINK@ \
-			| sed q \
-			| cut -d '/' -f 2 \
-			| xargs echo \
-			| sed s/'%'//
-		;;
-	*)	unknown_system ;;
-	esac; exit 0 ;;
-
-#
-# SYSTEM independent
-#
-+) "$argv0" r  "$2" ;;
--) "$argv0" r -"$2" ;;
+a*)
+	nonzero $2 && ! nonzero $3 && str isdigit "$2" \
+		|| usage
+	"$0".$VOLUME_SYSTEM "$@"
+	;;
+s*)
+	! nonzero $2 \
+		|| usage
+	"$0".$VOLUME_SYSTEM s
+	;;
 
 d*)
 	printf '$0: %s\nAudio system detected: %s\n' \
-		"$argv0" \
-		"$(system_determine)"
-	exit 0 ;;
+		"$0" \
+		$VOLUME_SYSTEM
+	;;
 
 m*) [ -z "$2" ] || usage
 	# restore previous volume if there is one
 	if [ -e "$VOLUME_TMP_FILE" ]; then
-		xargs "$argv0" a <"$VOLUME_TMP_FILE" \
+		xargs "$0" a <"$VOLUME_TMP_FILE" \
 			&& rm "$VOLUME_TMP_FILE" \
 			&& printf "Unmuted.\n" \
 			&& exit 0 \
@@ -120,7 +84,7 @@ m*) [ -z "$2" ] || usage
 
 	# dd used rather than shell redirect so it's easy to determine
 	# whether or not the file write worked
-	if ! printf "%b" "$("$argv0" s)" \
+	if ! printf "%b" "$("$0" s)" \
 				| dd of="$VOLUME_TMP_FILE" 2>/dev/null
 	then
 		printf "Error writing to file.\n" 1>&2
@@ -128,18 +92,21 @@ m*) [ -z "$2" ] || usage
 	fi
 
 	# and then of course mute
-	"$argv0" a 0
+	"$0" a 0
 	printf "Muted.\n"
 
 	exit 0 ;;
 
 r*)
-	set -x
-	argv2="$(printf "%s\n" "$2" | tr - _)"
-	! newval=$(printf "%s %s + p\n" $("$argv0" s) "$argv2" | dc) \
-		&& printf "%b: Error finding new value for volume.\n" "$argv0" \
-		&& exit 1
-	"$argv0" a "$newval"
+	nonzero $2 && ! nonzero $3 \
+			&& str isdigit "$(printf "%s\n" "$2" | sed 's/^\-//')" \
+		|| usage
+
+	"$0" a \
+		"$(printf "%s %s + p\n" \
+				$("$0" s) \
+				"$(printf "%s\n" $2 | tr - _)" \
+			| dc)"
 	exit $? ;;
 
 *)	usage ;;

src/nonzero.c

@@ -1,3 +1,3 @@
 int main(int argc, char *argv[]){
-	return argc > 1;
+	return !(argc > 1);
 }