HTTP: // superuser.com/questions/96151/how-do-i-check-whether-i-am-using-kde-or-gnome KDE with QT-based do have fewer and fewer people.
1) pgrep -l "gnome|kde|mate|cinnamon|lxde|xfce|jwm"
2) ps -A | egrep -i "gnome|kde|mate|cinnamon|lxde|xfce|jwm"
3) ls /usr/bin/*session*
Side effects are: