/usr/bin/android-gadget-service is in dbus-property-service 0.9.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 | #! /bin/sh
set -e
ACTION=""
SERVICE=""
cleanup()
{
    [ $? != "0" ] && STATUS="failed:" || STATUS="succeeded" exit 0
    echo "$(basename $0) $STATUS $ERROR"
}
trap cleanup EXIT INT QUIT ILL KILL SEGV TERM
while [ $# -gt 0 ]; do
       case "$1" in
               enable)
                       ACTION=true
                       [ -n "$2" ] && SERVICE=$2 shift || ERROR="enable: need service name" exit 1
                       ;;
               disable)
                       ACTION=false
                       [ -n "$2" ] && SERVICE=$2 shift || ERROR="enable: need service name" exit 1
                       ;;
               status)
                       ACTION=status
                       [ -n "$2" ] && SERVICE=$2 shift || ERROR="status: need service name" exit 1
                       ;;
                *help)
                       echo "usage: $(basename $0) [enable|disable|status] [adb|mtp|ptp|rndis]"
                       exit 0
                       ;;
               *)
                       ERROR="$1 is unknown" exit 1
                       ;;
       esac
       shift
done
[ -n "$ACTION" ] || ERROR="need an argument (enable/disable/status)" exit 1
[ -n "$SERVICE" ] || ERROR="need a service name (mtp/adb/ptp/rndis)" exit 1
case $ACTION in
    status)
        retval="$(dbus-send --system --print-reply \
		--dest="com.canonical.PropertyService" \
            	/com/canonical/PropertyService \
		com.canonical.PropertyService.GetProperty \
		string:$SERVICE|tail -1)"
	[ -n "$( echo $retval| grep true)" ] && echo "$SERVICE enabled"
	[ -n "$( echo $retval| grep false)" ] && echo "$SERVICE disabled"
        ;;
    true|false)
        retval=$(dbus-send --system --print-reply \
		--dest="com.canonical.PropertyService" \
            	/com/canonical/PropertyService com.canonical.PropertyService.SetProperty \
		string:$SERVICE boolean:$ACTION|tail -1|grep true)
	exec $0 status $SERVICE
        ;;
esac
exit 0
 |