The following works:
BUT the crontab never shows the notification. Why?
*/1 * * * * bash ~/Documents/test.sh
To execute any GUI related app from Cron you should export few desktop environment variables. The below solution is based on this answer where are provided more details.
crontabin Ubuntu 16.04, 17.10, 18.04 and other Ubuntu distributions with Gnome
#!/bin/bash -e # NAME: gui-launcher # Check whether the user is logged-in while [ -z "$(pgrep gnome-session -n -U $UID)" ]; do sleep 3; done # Export the current desktop session environment variables export $(xargs -0 -a "/proc/$(pgrep gnome-session -n -U $UID)/environ") # Execute the input command nohup "$@" >/dev/null 2>&1 & exit 0
gnome-sessionin this part
$(pgrep gnome-session -n -U $UID)with the name of the process of the DE in use, for example
mate-session. A list of the most Ubuntu DE is presented here. Lubuntu implementation of the same script - here. The script could be used to launch GUI app from TTY or SSH session in the current user's Desktop session.
chmod +x gui-launcher.
Then use it within
crontab in this way:
*/1 * * * * /full/path/to/gui-launcher "/full/path/to/the-targer-application"
Here is how it works on Ubuntu 17.10 on Wayland:
Here is presented an implementation of the same script over SSH: How to run script (.sh) files in a new terminal after connecting to Ubuntu 16.04 server via ssh?
Here are presented more explanations: Cron job to run python script at reboot does not work.
And one more example: Adjust brightness with xrandr and cron job