Can Cron Jobs Use Gnome-Open? - bash

Question

I am running Ubuntu 11.10 (Unity interface) and I created a Bash script that uses 'gnome-open' to open a series of web pages I use every morning. When I manually execute the script in the Terminal, the bash script works just fine. Here's a sample of the script (it's all the same so I've shortened it):
#!/bin/bash
gnome-open 'https://docs.google.com';
gnome-open 'https://mail.google.com';
Since it seemed to be working well, I added a job to my crontab (mine, not root's) to execute every weekday at a specific time.
Here's the crontab entry:
30 10 * * 1,2,3,4,5 ~/bin/webcheck.sh
The problem is this error gets returned for every single 'gnome-open' command in the bash script:
GConf-WARNING **: Client failed to connect to the D-BUS daemon:
Unable to autolaunch a dbus-daemon without a $DISPLAY for X11
GConf Error: No D-BUS daemon running
Error: no display specified
I did some searching to try and figure this out. The first thing I tried was relaunching the daemon using SIGHUP:
killall -s SIGHUP gconfd-2
That didn't work so I tried launching the dbus-daemon using this code from the manpage for dbus-launch:
## test for an existing bus daemon, just to be safe
if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
## if not found, launch a new one
eval `dbus-launch --sh-syntax --exit-with-session`
echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
fi
But that didn't do anything.
I tried adding simply 'dbus-launch' at the top of my bash script and that didn't work either.
I also tried editing the crontab to include the path to Bash, because I saw that suggestion on another thread but that didn't work.
Any ideas on how I can get this up and running?

Answer 1

Here is how the problem was solved. It turns out the issue was primarily caused by Bash not having access to an X window session (or at least that's how I understood it). So my problem was solved by editing my crontab like so:
30 10 * * 1,2,3,4,5 export DISPLAY=:0 && ~/bin/webcheck.sh
The "export DISPLAY=:0" statement told cron which display to use. I found the answer on this archived Ubuntu forum after searching for "no display specified" or something like that:
http://ubuntuforums.org/archive/index.php/t-105250.html
So now, whenever I'm logged in, exactly at 10:30 my system will automatically launch a series of webpages that I need to look at every day. Saves me having to go through the arduous process of typing in my three-letter alias every time :)

Answer 2

Glad you asked!
It depends on when it is run.
If the Gnome GDM Greeter is live, you can use the DBUS session from the logon dialog, if you will. You can, e.g., use this to send notifications to the logon screen, if no-one is logged in:
function do_notification
{
for pid in $(pgrep gnome-session); do
unset COOKIE
COOKIE="$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$pid/environ|cut -d= -f2-)"
GNUSER="$(ps --no-heading -o uname $pid)"
echo "Notifying user $GNUSER (gnome-session $pid) with '$#'"
sudo -u "$GNUSER" DBUS_SESSION_BUS_ADDRESS="$COOKIE" /usr/bin/notify-send -c "From CRON:" "$#"
done
unset COOKIE
}
As you can see the above code simply runs the same command (notify-send) on all available gnome-sessions, when called like:
do_notification "I wanted to let you guys know"
You can probably pick this apart and put it to use for your own purposes.