An X-based application which spawns off other Unix processes which 
continue to run after it is closed typically does not vanish until all of its 
children are terminated; the children inherit from the parent the open X 
connection to the display. 
	What you need to do is fork; then, immediately, in the child process, 
		close (ConnectionNumber(XtDisplay(widget)));
to close the file-descriptor in the display information. After this do your 
exec. You will then be able to exit the parent.
	Alternatively, before exec'ing make this call, which causes the file 
descriptor to be closed on exec.
		(void) fcntl(ConnectionNumber(XDisplay), F_SETFD, 1);

[Thanks to Janet Anstett (anstettj@tramp.Colorado.EDU), Gordon Freedman 
(gjf00@duts.ccc.amdahl.com); 2/91. Greg Holmberg (holmberg@frame.com), 3/93.]