Notify-send doesn't work from crontab

Things seem to be different on 13.04, at least in Gnome Shell.

First, this is what env prints when run from user zzyxy's (not root's) cron job:

HOME=/home/zzyxy
LOGNAME=zzyxy
PATH=/usr/bin:/bin
XDG_RUNTIME_DIR=/run/user/zzyxy
LANG=en_US.UTF-8
SHELL=/bin/sh
PWD=/home/zzyxy

To get notify-send to work, it seems to be necessary to set the DBUS_SESSION_BUS_ADDRESS environment variable, as per DahitiF's comment on ubuntuforums.org. Just prepend the following to your actual job description:

eval "export $(egrep -z DBUS_SESSION_BUS_ADDRESS /proc/$(pgrep -u $LOGNAME gnome-session)/environ)";

It doesn't seem to be necessary to set DISPLAY.

Command notify-send would not show the message on your screen when started by cron. Just add target display at the top of your script, for example:

export DISPLAY=:0

Commands need to reference their location. So notify-send needs to be /usr/bin/notify-send

All commands need to have their full path.

Use the whereis notify-send command to see where your commands "live"