• getMainDevice ?-v?
Return a list containing the x-coord and y-coord of the origin and the width and height of the rectangle defining the main screen. The main screen refers to the screen containing the window that is currently receiving keyboard events.
If the -v option is specified, return only the visible frame: in that case, the returned rectangle is always based on the current user-interface settings and does not include the area currently occupied by the dock and menu bar.
If you need to get the frame dimensions of another screen (in a multi display installation), see the [screen] command.