#include <stdio.h>
#include <err.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

#define __O_TMPFILE 020000000
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
#define AT_EMPTY_PATH 0x1000

int main(int argc, char **argv)
{
  char buf[128];

  if (argc != 4)
    errx(1, "Usage: flinktest TMPDIR PATH linkat|proc");

  int fd = open(argv[1], O_TMPFILE | O_RDWR, 010600);
  if (fd == -1)
    err(1, "O_TMPFILE");
  write(fd, "test", 4);

  if (!strcmp(argv[3], "linkat")) {
    if (linkat(fd, "", AT_FDCWD, argv[2], AT_EMPTY_PATH) != 0)
      err(1, "linkat");
  } else if (!strcmp(argv[3], "proc")) {
    sprintf(buf, "/proc/self/fd/%d", fd);
    if (linkat(AT_FDCWD, buf, AT_FDCWD, argv[2], AT_SYMLINK_FOLLOW) != 0)
      err(1, "linkat");
  } else {
    errx(1, "invalid mode");
  }
  return 0;
}