Check the variable
window-system or the function
display-graphic-p. Either will give you
nil if you run Emacs with
window-system is a variable defined in `C source code'.
Its value is x
It is a terminal-local variable; global value is the same.
Name of window system through which the selected frame is displayed.
The value is a symbol:
nil for a termcap frame (a character-only terminal),
'x' for an Emacs frame that is really an X window,
'w32' for an Emacs frame that is a window on MS-Windows display,
'ns' for an Emacs frame on a GNUstep or Macintosh Cocoa display,
'pc' for a direct-write MS-DOS frame.
Use of this variable as a boolean is deprecated. Instead,
display-graphic-p' or any of the otherdisplay-*-p'
predicates which report frame's specific UI-related capabilities.
(display-graphic-p &optional DISPLAY)
Return non-nil if DISPLAY is a graphic display.
Graphical displays are those which are capable of displaying several
frames and several different fonts at once. This is true for displays
that use a window system such as X, and false for text-only terminals.
DISPLAY can be a display name, a frame, or nil (meaning the selected