EOF is level triggered for read and for kevent

eof.c

#include <stdio.h>
#include <strings.h>
#include <assert.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>

void setNonBlock(int fd) {
  int flags = fcntl(fd, F_GETFL, 0);
  assert(flags >= 0);
  assert(fcntl(fd, F_SETFL, flags | O_NONBLOCK) == 0);
}

int main (int argc, char **argv) {
  int fd[2], kq;
  char readBuf[100];

  // Make a socket pair, set nonblocking.
  assert(0 == socketpair(PF_LOCAL, SOCK_STREAM, 0, fd));
  setNonBlock(fd[0]);
  setNonBlock(fd[1]);

  // Listen for read events on fd[1]
  kq = kqueue();
  struct kevent kqReads[1];
  bzero(kqReads, sizeof(struct kevent) * 1);
  kqReads[0].ident = fd[1];
  kqReads[0].filter = EVFILT_READ;
  kqReads[0].flags = EV_ADD;
  struct kevent events[1];
  const struct timespec kev_time = { 0, 0 };
  assert(0 == kevent(kq, kqReads, 1, events, 1, &kev_time));

  // Try reading from both fds, should get EWOULDBLOCK
  assert(-1 == read(fd[0], readBuf, 100));
  assert(errno == EWOULDBLOCK);
  assert(-1 == read(fd[1], readBuf, 100));
  assert(errno == EWOULDBLOCK);

  // SHUT_RDWR fd[0].  fd[1] should start getting EOF, and EVFILT_READ
  assert(0 == shutdown(fd[0], SHUT_RDWR));
  assert(1 == kevent(kq, NULL, 0, events, 1, &kev_time));
  assert(events[0].ident == fd[1]);
  assert(events[0].filter == EVFILT_READ);

  // Continue polling.  EOF is "level-triggered":
  //   - Keep reading from fd[1], keep getting EOF.
  //   - Keep checking for kevents, keep getting EVFILT_READ.
  assert(0 == read(fd[1], readBuf, 100));
  assert(1 == kevent(kq, NULL, 0, events, 1, &kev_time));
  assert(events[0].ident == fd[1]);
  assert(events[0].filter == EVFILT_READ);
  assert(0 == read(fd[1], readBuf, 100));
  assert(1 == kevent(kq, NULL, 0, events, 1, &kev_time));
  assert(events[0].ident == fd[1]);
  assert(events[0].filter == EVFILT_READ);
  assert(0 == read(fd[1], readBuf, 100));
  assert(1 == kevent(kq, NULL, 0, events, 1, &kev_time));
  assert(events[0].ident == fd[1]);
  assert(events[0].filter == EVFILT_READ);

  return 0;
}