Synopsis:
   $gui()

Technical:
   Returns true if the client is a GUI client.

Practical:
   If this function returns true, the client is a GUI client.  Either
   Presentation Manager, GTK or any other GUIs that get added. This function
   is here to allow scripts to know whether the client they are being run 
   on have the necessary functionality to execute graphical functions.

Returns:
   > 0   client is a GUI client
     0   client is not a GUI client

See Also:
   Special_Vars(7)