sudo mkdir /media/MP840

UUID=2408-0200 /media/MP840 vfat noauto,async,rw,user,dmask=000,fmask=111,utf8,codepage=866 0 0

KERNEL=="sd?1", ENV{ID_FS_UUID}=="2408-0200", RUN+="/bin/su username -c '/home/username/MySync/TranscendMP840/sdcard/sync-to-player.sh'"

#!/bin/bash
set -e  # abort if any command failed

# MP3 player must be attached to the USB
if [ ! -b /dev/disk/by-uuid/2408-0200 ]
then
    echo "MP840 is not attached"
    exit 1
fi

# /etc/fstab:
#    UUID=2408-0200 /media/MP840 vfat noauto,async,rw,user,dmask=000,fmask=111,utf8,codepage=866 0 0
mount /media/MP840

# the flag file must be created on the device root
if [ ! -f /media/MP840/rsync-accept.flag ]
then
    echo "The flag file on the MP840 is missing"
    umount -l /media/MP840
    exit 1
fi

# detect the dbus session of the current user
USERNAME=`whoami`
export DBUS_SESSION_BUS_ADDRESS=`ps -u $USERNAME e | grep -Eo 'dbus-daemon.*address=unix:abstract=/tmp/dbus-[A-Za-z0-9]{10}' | tail -c35`
# for kde5 because previous recept is not working
if [ -z "$DBUS_SESSION_BUS_ADDRESS" ]
then
  pid=$(pgrep -u $USERNAME kdeconnectd)
  dbus=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$pid/environ | sed 's/DBUS_SESSION_BUS_ADDRESS=//' )
  export DBUS_SESSION_BUS_ADDRESS=$dbus
fi

# notification of the beginning of the synchronization
echo "Synchronization is beginning"
espeak -p 1 "Synchronization is beginning"
if [ ! -z "$DBUS_SESSION_BUS_ADDRESS" ]
then
    notify-send "MP3 Player MP840" "Synchronization is beginning..."
fi

# synchronization: mirror
rsync -vr --delete --size-only /home/username/MySync/TranscendMP840/sdcard/ /media/MP840/sdcard/

# operation may take a long time, due to `async` in the /etc/fstab
umount -l /media/MP840

# notification of the completion of synchronization
echo "Synchronization is complete"
espeak -p 1 "Synchronization is complete"
if [ ! -z "$DBUS_SESSION_BUS_ADDRESS" ]
then
    notify-send "MP3 Player MP840" "Synchronization is complete!"
fi

# all is well
exit 0