title: How to append to a file with fstream fstream::app flag seems not to work
body: <p>i simply want to write (append) to a logfile. I looked it up here:<br>
  <a href="http://www.cplusplus.com/reference/iostream/fstream/open/" rel="noreferrer">http://www.cplusplus.com/reference/iostream/fstream/open/</a></p>
  
  <p>so this is  what  i did</p>
  
  <pre><code>#include &lt;fstream&gt;
  
  fstream outfile;
  
  //outfile.open("/tmp/debug.txt" );  // works, simply for writing
  outfile.open("/tmp/debug.txt", fstream::app );  // does nothing
  
  outfile &lt;&lt; "START" &lt;&lt; endl;
  
  outfile.close();
  </code></pre>