Desktop Notifications From Script

Gordoon · 06-13-2015, 09:45 AM

I am running an APC UPS for my home VOIP equipment. My Ubuntu 14.04 LTS computer with apsupsd is also plugged into this UPS, and I have modified apcupsd's onbattery script to shutdown the computer 1 minute after the UPS goes on battery. I want to send a desktop notification to warn when the computer is set to shut down. I have tried adding notify-send, zenity and xmessage lines to the onbattery script - they all send a notifications successfully when I run the onbattery script from terminal, but none work when apccontrol calls the script when the UPS goes on battery. The shutdown command in the onbattery script does work when I unplug the UPS. Why would notifications work when I run the script from terminal and not when script is run from apccontrol?

Code:

#!/bin/sh
#
# This shell script if placed in /etc/apcupsd
# will be called by /etc/apcupsd/apccontrol when the UPS
# goes on batteries.
#
sudo shutdown -P 1
exit 0

ljb643 · 06-14-2015, 08:15 PM

To work, notify-send needs to send a message over the D-bus session bus to a notification server such as xfce4-notifyd. I don't know that much about it, but as far as I know it is not possible for a process which is not part of the session (a child or descendent of the first post-login process, or something like that) to do that. Your apcupsd runs outside the session, of course, so I don't think it has any way to talk to the session D-bus.

Different problem for Xmessage, but still, it would need to communicate with the X server, and permissions are set up to prevent that - using the Xauthority mechanism.

I realize this isn't much help at all.