시스템프로그래밍 link와 unlink 질문입니다

#include <sys/types.h>  /* unlink.c */
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include "error.h"
 
int main()
{
  int fd, len;
  char buf[20];
 
  fd = open("tempfile", O_RDWR | O_CREAT | O_TRUNC, 0666);
  if (fd == -1) error("open1");
  unlink("tempfile");
  len = write(fd, "How are you?", 12);
  if (len != 12) error("write");
  lseek(fd, 0L, SEEK_SET);
  len = read(fd, buf, sizeof(buf));
  if (len < 0) error("read");
  buf[len] = '\0';
  printf("%s\n", buf);
  close(fd);
  fd = open("tempfile", O_RDWR);
  if (fd == -1) error("open2");
  close(fd);
  return 0;
}