Cron-GIU-Launcher is a simple Bash script, that is able to launch a GUI application as Cron job within Ubuntu. The script is designed to work with the user's environment, respectively the Cron jobs shall be set within user's crontab file. It codld be modified to work with cron.d, but in some cases this will cause mishmash with the file permissions within /proc, so it is not good idea.

• $1 - list of commands to be executed. The individual commands need to be separated with ␣&&␣ - note the spaces.
• $2 - short description of the job that will be appended to the log file name. Read the the section How it works?
• $3 - time-out in minutes, when the user is not logged in. While this variable is empty there is no time-out. If the job is on @reboot this variable should be empty. This option is usefull for regular Cron jobs, for example: If you have a job that is executed every 15 minutes and your user is logout (or locked) for 2 hours there will have 8 pending jobs, which will be execited when the user is logged on.

Befor crating a Cron job that uses Cron-GIU-Launcher with Cron

0. Note about the logging: The script will create a log file located in /tmp, which name shall be

   $USER-cron-gui-launcher-$DESCRIPTION.log

   • Where as $DESCRIPTION will be assigned the value of the input variable $2, thus if you wish you can make some job's log file unique.

1. Initially the script attempts to get the current user's $DISPLAY number. For this purpose it uses the following method:

   w $(id -un) | awk 'NF > 7 && $2 ~ /tty[0-9]+/ {print $3; exit}'

   • The $DISPLAY variable is unset while the user is not logged in. In this case the scipt sleep's for a while and then makes a new attept.

   • This action is repeated until the $DISPLAY variable is set, then its value is saved and exported.

2. Create an array of the values of the envvar $XDG_CURRENT_DESKTOP from each /proc/$ProcessNumber/environ file. The command pgrep -U "$UID" creates a list of all $USER's processes. The function get_environ() is executed for each $USER's process and its output is stored into the temporal array XDG_CURRENT_DESKTOP+=$().

3. Get the name of the current Desktop Environment. Get the most frequent value from the array created in step 2. This is the way, used here, to find the current DE when it is changed a little bit ago. The function get_frequent() is used here and its output is stored as value of the variable $XDG_CURRENT_DESKTOP.

4. Filter the value of the variable $XDG_CURRENT_DESKTOP and set the result as value of the triger $DE.

5. Export the current user's desktop-session environment variables. The commands as pgrep gnome-session -n -U $UID gets the current user's desktop-session process number, then the function export_environ() reads the content of /proc/$ProcessNumber/environ and export its content line by line.

6. Execute the list of the input commands. Fragmentation of the list of the input commands (input variable "$1"), use && as separator, then execute each one by the function execute_input_commands().

$(pgrep gnome-session -n -U $UID)	[Ubuntu Unity] [Ubuntu Gnome Desktopt] [Gnome Classic | Flashbach (compis|metacity)] (Openbox) [Budgie]
$(pgrep gnome-session-b -n -U $UID) 	This the full name of the proccess!
$(pgrep budgie-daemon -n -U $UID)	[Budgie] but $(pgrep gnome-session -n -U $UID) is better choice
$(pgrep xfce4-session -n -U $UID)	[Xubuntu] [XFCE4]
$(pgrep mate-session -n -U $UID)	[Ubuntu MATE] (Openbox)
$(pgrep lxsession -n -U $UID)		[Lubuntu] [Lubuntu Netbook] [LXDE]
$(pgrep lxqt-session -n -U $UID)	[LXQt]
$(pgrep cinnamon-sessio -n -U $UID)	[Cinnamon] [Cinnamon2d] [Cinnamon (Software Rendering)]
$(pgrep startkde -n -U $UID)		[Kubuntu] [KDE Plasma] (Openbox)
$(pgrep start-lumina-de -n -U $UID)	[Lumina]  (The Lumina® Desktop Environment)
$(pgrep fluxbox -n -U $UID)		[Fluxbox] (The Lumina® Desktop Environment)
$(pgrep xmonad -n -U $UID)		[Xmonad]
$(pgrep subtle -n -U $UID)		[Subtle]
$(pgrep awesome -n -U $UID)		[Awesome]
$(pgrep enlightenment -n -U $UID)	[Enlightenment]
$(pgrep i3bar -n -U $UID)		[i3wm]
$(pgrep openbox -n -U $UID)		[Openbox] [GNOME/Openbox KDE/Openbox]
$(pgrep starttde -n -U $UID)		[Trinity]

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