At work we use a Jabber instant messenger (IM) server for internal company communications, so that regardless of whether someone is in the office, working from home, or on the road, they can be reached via IM.
I’m running Ubuntu both at work and at home and I use the Pidgin IM client to talk to the Jabber server. I work from home on Thursdays, and I’m always forgetting to turn Pidgin off when I leave work on Wednesday. I usually end up ssh-ing into my work box from home and killing the Pidgin client off remotely, but sometimes I forget and when I come back to work on Friday there are a half-dozen “Are you there?” -type messages on my Pidgin work-client.
So I figured I’d automate the process, automatically setting Pidgin status to “Away” and “Available” using cron, turning the work-client off entirely on Thursdays and weekends, and automatically turning the home-client on Thursday mornings and off Thursday night.
I did a little digging and found a command-line program called purple-remote that allows me to automatically update the Pidgin status and message lines. The purple-remote program is included in the libpurple-bin package, which I installed with System > Administration > Synaptic Package Manager.
Once purple-remote was installed, I fired up a terminal and did a little experimenting on the command line. I found I could set Pidigin’s status to “Away” and the status message to “At lunch” by typing:
/usr/bin/purple-remote "setstatus?status=away&message=At lunch"
I could set the status to “Available” and blank the status message by typing:
/usr/bin/purple-remote "setstatus?status=available&message="
So far so good. I can also cause Pidgin to exit with:
/usr/bin/purple-remote "quit"
Starting Pidgin is just a matter of running:
/usr/bin/pidgin
Time to set up the cron jobs. I fired up crontab -e and entered:
# IM Status SHELL=/bin/bash 00 08 * * Mon,Fri /usr/bin/pidgin & 01 08 * * Mon,Tue,Wed,Fri /usr/bin/purple-remote "setstatus?status=away&message=" 00 09 * * Mon,Tue,Wed,Fri /usr/bin/purple-remote "setstatus?status=available&message=" 30 13 * * Mon,Tue,Wed,Fri /usr/bin/purple-remote "setstatus?status=away&message=At lunch" 30 14 * * Mon,Tue,Wed,Fri /usr/bin/purple-remote "setstatus?status=available&message=" 30 17 * * Mon,Tue,Wed,Fri /usr/bin/purple-remote "setstatus?status=away&message=" 00 19 * * Wed,Fri /usr/bin/purple-remote "quit"
This would start Pidgin at 8:00am, set my status to “Away” at 8:01am, “Available” at 9:00am, “Away – At lunch” at 1:30pm, “Available” again at 2:30pm, “Away” at 5:30pm. On Wednesday and Friday nights at 7:00pm the client shuts down entirely, on Monday and Friday mornings Pidgin gets restarted. That will leave the client off all day on Thursdays and on weekends when I’m not at the office. If my schedule changes for any reason I can still update my status in Pidgin manually.
Looks good, but this doesn’t work. Although the commands listed above work just fine on the command line, they’d fail when they were executed from cron. Checking my mail I found error messages like this:
Traceback (most recent call last):
File "/usr/bin/purple-remote", line 16, in
obj = dbus.SessionBus().get_object("im.pidgin.purple.PurpleService",
"/im/pidgin/purple/PurpleObject")
File "/var/lib/python-support/python2.5/dbus/_dbus.py", line 218, in __new__
mainloop=mainloop)
File "/var/lib/python-support/python2.5/dbus/_dbus.py", line 107, in __new__
bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
File "/var/lib/python-support/python2.5/dbus/bus.py", line 121, in __new__
bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ExecFailed:
dbus-launch failed to autolaunch D-Bus session: Autolaunch error:
X11 initialization failed.
The key part of that message is “dbus-launch failed to autolaunch D-Bus session: Autolaunch error: X11 initialization failed.” dbus is a messaging system, and X11 is the implementation of X-Windows Ubuntu uses, which is what the Gnome desktop runs on. Pidgin is an application running on the Gnome desktop / X-Windows. The error message is saying that the program failed to send a message to X11 (X-Windows) and on to Pidgin.
There are three problems here:
- The first is that in order for purple-remote to send messages to Pidigin via DBUS it has to work it needs to know the value of the DBUS_SESSION_BUS_ADDRESS environment variable. (Kudos to explicitly ambiguous and his article at http://ubuntuforums.org/showthread.php?t=632580 for pointing me towards this solution.)
- In order to start Pidgin at 8:00am Pidgin needs to know the value of the of the XAUTHORITY environment variable otherwise it won’t be authorized to start up on a screen that I’m logged into.
- In order to start Pidgin at 8:00am Pidgin needs to know the value of the DISPLAY environment variable so it knows what screen to start up on.
When you start up Ubuntu the dbus daemon starts up and creates a unique session address. Your applications have to know this session address in order to send messages using the daemon. The address is stored in the DBUS_SESSION_BUS_ADDRESS environment variable when you log in, so if you try to run an application from the command line it gets the session address from the DBUS_SESSION_BUS_ADDRESS environment variable. Since cron runs in it’s own environment it doesn’t know the value of DBUS_SESSION_BUS_ADDRESS, so programs that depend on dbus fail when you try to run them from a cron job.
You can see the value by typing:
> env | grep DBUS_SESSION_BUS_ADDRESS DBUS_SESSION_BUS_ADDRESS=unix:abstract= /tmp/dbus-AmUs20000,guid=6cce82d52ca190000000000000000000
Likewise, the value of XAUTHORITY changes every time you restart your computer. You can see the current value by typing:
> env | grep XAUTHORITY
DISPLAY remains the same between reboots. To get the value for your system, type:
> env | grep DISPLAY DISPLAY=:0.0
Add the “DISPLAY=:0.0” line at the beginning of your crontab file and it’ll be set for Pidgin.
In order to make the environment variables available to cron jobs I created the program ~/bin/export_x_info which looks like this:
#!/bin/bash # Export the dbus session address on startup so it can be used by cron touch $HOME/.Xdbus chmod 600 $HOME/.Xdbus env | grep DBUS_SESSION_BUS_ADDRESS > $HOME/.Xdbus echo 'export DBUS_SESSION_BUS_ADDRESS' >> $HOME/.Xdbus # Export XAUTHORITY value on startup so it can be used by cron env | grep XAUTHORITY >> $HOME/.Xdbus echo 'export XAUTHORITY' >> $HOME/.Xdbus
Create this script, type chmod 700 ~/bin/export_x_info so you can execute it, then execute it, then add it to System > Preferences > Sessions > Startup Programs so it will execute every time you start your computer and record the latest session address and XAUTHORITY value.
This script creates a 4-line file ~/.Xdbus with the current session address and XAUTHORITY value. By sourcing this file in the crontab file your scripts can now use dbus to send messages to X-Windows applications. My final crontab file looks like this:
SHELL=/bin/bash DISPLAY=:0.0 # IM Status 00 08 * * Mon,Fri source ~/.Xdbus; /usr/bin/pidgin & 01 08 * * Mon,Tue,Wed,Fri source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=away&message=" 00 09 * * Mon,Tue,Wed,Fri source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=available&message=" 30 13 * * Mon,Tue,Wed,Fri source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=away&message=At lunch" 30 14 * * Mon,Tue,Wed,Fri source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=available&message=" 30 17 * * Mon,Tue,Wed,Fri source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=away&message=" 00 19 * * Wed,Fri source ~/.Xdbus; /usr/bin/purple-remote "quit"
The call to source ~/.Xdbus on each line loads the DBUS_SESSION_BUS_ADDRESS and XAUTHORITY environment variables before executing the purple-remote command or starting Pidgin.
Now the cron works and my Pidgin status is constantly updated. The cron on my home computer is much simpler:
SHELL=/bin/bash DISPLAY=:0.0 # IM Status 00 08 * * Thu source ~/.Xdbus; /usr/bin/pidgin & 01 08 * * Thu source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=away&message=" 00 09 * * Thu source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=available&message=" 30 13 * * Thu source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=away&message=At lunch" 30 14 * * Thu source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=available&message=" 30 17 * * Thu source ~/.Xdbus; /usr/bin/purple-remote "setstatus?status=away&message=" 00 19 * * Thu source ~/.Xdbus; /usr/bin/purple-remote "quit"
The same technique works for other X-Windows programs as well. For instance, I added this line to my cron:
30 17 * * Mon,Tue,Wed,Fri source ~/.Xdbus; /usr/bin/notify-send "Go Home" "Time to Go"
So every day at 5:30pm a “notify” message pops up reminding me that it’s time to go home.
Hope you find this useful.