gsettings change background every user gnome-session

#!/bin/bash

# Dawid Mocek
# Req. gnome-session needs to be running(check ps aux |grep gnome-session)

BACKGROUND="/usr/share/backgrounds/zso.jpg"
PIDS=$(pgrep gnome-session)

for PID in $PIDS; do

    BUS_ADDRESS=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$PID/environ | cut -d= -f2-)
    BUS_USER=$(grep -z USER /proc/$PID/environ | cut -d= -f2-)
    # echo $PID" "$BUS_ADDRESS" "$BUS_USER
    su --login $BUS_USER  <<EOF
export DBUS_SESSION_BUS_ADDRESS=$BUS_ADDRESS
if [[ $(gsettings get org.gnome.desktop.background picture-uri) != "'file://"$BACKGROUND"'" ]]; then gsettings set org.gnome.desktop.background picture-uri file://$BACKGROUND; fi
EOF
# ^ Przed markerem EOF i pomiedzy <<EOF [...]EOF przed komendami w bloku zawartymi nie moze byc bialego znaku !
done