#include <fcntl.h>
#include <unistd.h>
int main() {

  int fd = open("data.txt", O_RDONLY);
  while (1) {
    char buf[256];
    int cnt = read(fd, buf, 256);
    if (cnt <= 0)
      break;
    write(1, buf, cnt);
  }
  close(fd);
  
  return 0;
}