TIOCNOTTY?

[Mark Andrews]

	TIOCNOTTY dissasociates the calling process from the starting
    tty.

	{	/* associated with the starting tty */
	int fd;
		if( (fd = open("/dev/tty",0)) < 0)
			err("can`t open /dev/tty");
		else
		{
			(void)ioctl(fd,TIOCNOTTY,(char *)0);
			(void)close(fd);
		}
	}	/* unassociated with any tty */