PFD_GREYBACK
pfd[PFD_GREYBACK].fd = greyback[1];
pfd[PFD_GREYBACK].events = POLLIN;
pfd[PFD_GREYBACK].fd = -1;
pfd[PFD_GREYBACK].events = 0;
if (pfd[PFD_GREYBACK].revents & (POLLIN|POLLHUP))