无法初始化libxfconf：没有收到回复

Question

在剧本中：

if [ -z "${DBUS_SESSION_BUS_ADDRESS}" ] ; then
. ${HOME}/.dbus/session-bus/`ls -rt ${HOME}/.dbus/session-bus/ | tail -1`
export DBUS_SESSION_BUS_ADDRESS
fi
DESKTOP=:0.0 xfconf-query -c xfce4-desktop -p /backdrop/screen0/monitor0/image-path -s '/home/user-name/Desktop/b84.png'

在crontab -e：

* * * * * /bin/bash -c '/home/user-name/cronBackground.sh >> ~/this.txt 2>&1'

我在这里做错了什么xD