I was wondering what commands/utilities can be used in terminal to know the types of windowing system (such as X window system), window manager (such as Metacity, KWin, Window Maker) and desktop environment (such as KDE, Gnome) of a Linux or other Unix-like operating systems?
From Ask Ubuntu.SE: If you have
wmctrl -m will identify the window manager for you.
Thomas already mentioned the
XDG_CURRENT_DESKTOP environment variable for identifying the desktop environment.
And from this thread here in Unix & Linux SE: the
XDG_SESSION_TYPE environment variable can be used to identify whether the windowing system is X11 or Wayland.