newfd->id = uxsel_input_add(fd, rwx);
void uxsel_set(int fd, int rwx, uxsel_callback_fn callback){    struct fd *newfd = snew(struct fd);    struct fd *oldfd;    newfd->fd = fd;    newfd->rwx = rwx;    newfd->callback = callback;    oldfd = find234(fds, newfd, NULL);    if (oldfd) {	del234(fds, oldfd);	sfree(oldfd);    }    add234(fds, newfd);}