__fcntl
int flags = __fcntl (fd, F_GETFD);
__fcntl (fd, F_SETFD, FD_CLOEXEC);
__fcntl (fd, F_SETFD, FD_CLOEXEC);
__fcntl (child_end, F_SETFD, 0);
__fcntl (parent_end, F_SETFD, FD_CLOEXEC);
__fcntl (parent_end, F_SETFD, 0);