// cpp
#include <iostream>
#include <sys/timerfd.h>
#include <poll.h>
#include <unistd.h>
#include <assert.h>

using namespace std;

int main() {
 struct itimerspec timebuf;
 int timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
 timebuf.it_interval = {1, 0}; // period timeout value = 1s
 timebuf.it_value = {5, 100}; // initial timeout value = 5s100ns
 timerfd_settime(timerfd, 0, &timebuf, NULL);

 struct pollfd fds[1];
 int len = sizeof(fds) / sizeof(fds[0]);
 fds[0].fd = timerfd;
 fds[0].events = POLLIN | POLLERR | POLLHUP;

 while (true)
 {
 int n = poll(fds, len, -1);
 for (int i = 0; i < len && n-- > 0; ++i) {
 if (fds[i].revents & POLLIN)
 {
 uint64_t val;
 int ret = read(timerfd, &val, sizeof(val));
 if (ret != sizeof(val))
 {
 cerr << "read " << ret << "bytes instead of 8 frome timerfd" << endl;
 break;
 }
 cout << "timerfd = " << timerfd << " timeout!" << endl;
 }
 }
 }
 close(timerfd);
 return 0;
}