#include <sys/timerfd.h>

#include <err.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

int
main(void)
{
	int fd;
	struct timespec t0, t1, dt;
	const struct itimerspec its = {
		.it_value = { .tv_sec = 1, .tv_nsec = 0 },
		.it_interval = { .tv_sec = 0, .tv_nsec = 0 },
	};
	uint64_t v;
	ssize_t nread;
	int error;


	if ((fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC)) == -1)
		err(1, "timerfd_create");
	if (timerfd_settime(fd, /*flags (relative)*/0, &its, NULL) == -1)
		err(1, "timerfd_settime");
	if (clock_gettime(CLOCK_MONOTONIC, &t0) == -1)
		err(1, "clock_gettime");
	if ((nread = read(fd, &v, sizeof(v))) == -1)
		err(1, "read");
	if (clock_gettime(CLOCK_MONOTONIC, &t1) == -1)
		err(1, "clock_gettime");
	if ((size_t)nread != sizeof(v))
		errx(1, "bad read: %zd", nread);
	printf("%"PRIu64"\n", v);

	timespecsub(&t1, &t0, &dt);
	printf("%jd.%09ld\n", (intmax_t)dt.tv_sec, dt.tv_nsec);

	fflush(stdout);
	return ferror(stdout);
}