title: why fseek never return -1
body: <p>I am using ubuntu 14.04 and try to read binary file, but fseek never return -1 for out of file size. </p>
  
  <p>Why this happend? </p>
  
  <pre><code>#include &lt;stdio.h&gt;
  
  int main() {
      const char *fn = "myfile";
      FILE * fid;
      fid = fopen(fn, "r");
      int flag;
      while(1) {
          flag = fseek(fid, sizeof(float), SEEK_CUR);
          printf("flag: %d\n",flag);
          if(flag)
              break;
      }
  }
  </code></pre>