Using notify-send with cron

Question

I've been trying to use notify-send with cron. I've checked out tons of answers given on stackoverflow and other forums. But I don't see the notify-send popup appearing. I'm currently running Ubuntu 13.10. I've been able to get this to work earlier (about 3 months ago when I had Ubuntu 11.10) but I don't remember how and I don't see what I'm doing wrong here.

My current crontab looks like:

*/1 * * * * export DISPLAY=:0.0 && export XAUTHORITY=/home/harold/.Xauthority && /usr/bin/notify-send "$(date)"

I've tried many solutions given online including using sudo -u harold right before /usr/bin/notify-send .... I've also tried using export DISPLAY=:0 instead of =:0.0. The popup still doesn't appear.

I've also tried to create a script. The cron job to run the script looks like:

*/1 * * * * cd /home/harold/bin && ./notify-send-test.sh

And my script (notify-send-test.sh) looks like:

#!/bin/bash
#export DISPLAY=:0
#export XAUTHORITY=/home/harold/.Xauthority
/usr/bin/notify-send "$(date)"
echo "trying to notify at $(date)" >> /home/harold/bin/cronlog.txt

I've tried using the commented lines and not using them. None of the combinations seem to work. I've also tried using export DISPLAY=0.0.

I do get the expected output in the cronlog.txt file every minute. This means that my script is being executed but the notify-send is not.

I would like to know what I am doing wrong. Happy to provide any more information that may be of use.

Secondary question: There was also something about cron not being able to use certain environment variables. I don't get what that meant and how it affects the way I use cron. It would be nice if someone could explain this.

Answer 1

The DBUS_SESSION_BUS_ADDRESS env variable will not be set in cron daemon. Setting this value will fix your issue. Add the following changes to your .sh file and call it from crontab.

notify-send-test.sh

#!/bin/bash
username=$(/usr/bin/whoami)
pid=$(pgrep -u $username nautilus)
dbus=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$pid/environ | sed 's/DBUS_SESSION_BUS_ADDRESS=//' )
export DBUS_SESSION_BUS_ADDRESS=$dbus
/usr/bin/notify-send "$(date)"

Crontab

*/1 * * * * /home/harold/bin/notify-send-test.sh

Answer 2

To add to Sakthi's answer.

You can get the DBUS_SESSIONBUS_ADDRESS withouth using nautilus (or gnome or whatever) by typing dbus-launch (see this answer)

So to the script would simply be:

#!/bin/bash
export $(dbus-launch)
/usr/bin/notify-send "$(date)"

If that doesn't work, you could try setting it hard-coded to your user ID:

#!/bin/bash
userid=$(id -u)
DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/$userid/bus"
export DBUS_SESSION_BUS_ADDRESS
/usr/bin/notify-send "$(date)"

You can add echo $(env | grep DBUS_SESSION_BUS_ADDRESS) in the script to check what the env variable is when the script is executed.