Test inotify on memfd with epoll api

simple_epoll_inotify_test.c

#include <stdio.h>
#include <sys/inotify.h>
#include <sys/time.h>

#include <sys/epoll.h>
#include <errno.h>

#include <linux/memfd.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <unistd.h>
#ifdef __NR_memfd_create   // older glibc may not have this syscall defined
#define F_SEAL_SEAL 0x0001 /* prevent further seals from being set */
// Note that linux must be 3.17 or greater to support this
int memfd_create(const char *name, unsigned int flags) {
  return syscall(__NR_memfd_create, name, flags);
}
#endif



int inotify_init(void);
int inotify_add_watch(int fd, const char *pathname, uint32_t mask);

int main(int argc, char** argv)
{
  char buf[64];
  fd_set set;
  struct timeval timeout;
  FD_ZERO (&set);
  int fd = memfd_create("/foo", F_SEAL_SEAL);

  sprintf(buf, "/proc/self/fd/%d", fd);

  int inotify = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);

  if (inotify < 0) {
    printf("Err inotify_init1\n");
    return 1;
  }

  //uint32_t mask = IN_DELETE | IN_MODIFY | IN_MOVE | IN_ONLYDIR | IN_MOVE_SELF |
  //    IN_DELETE_SELF;

  int ret = inotify_add_watch(inotify, buf, IN_MODIFY);


  int epollfd = epoll_create1(EPOLL_CLOEXEC);
  if (epollfd < 0) {
    printf("ERR epoll_creat1\n");
    return 1;
  }

  // Add inotifyfd to epoll set
  struct epoll_event ev;
  //std::memset(&ev, 0, sizeof(ev));
  ev.events = EPOLLIN;
  ev.data.fd = inotify;
  if (epoll_ctl(epollfd, EPOLL_CTL_ADD, inotify, &ev) < 0) {
    printf("ERR epoll_ctl\n"); //<< ::strerror_r(errno, buf, sizeof(buf));
    return 1;
  }
  int kMaxEvents = 10;
  struct epoll_event events[kMaxEvents];

  int n;
  do {
    n = epoll_wait(epollfd, events, kMaxEvents, -1);
  } while (n < 0 && errno == EINTR);

  char dbuf[1024];
  for (int i = 0; i < n; ++i) {
    int ifd = events[i].data.fd;
    read(fd, dbuf, sizeof(dbuf));
    printf("Read %s from %d\n", dbuf, fd);
  }

}