title: What does "%.6d" mean in printf
body: <p>What does <code>%.6d</code> mean in:</p>
  
  <pre><code>printf("%s.%.6d len:%d ", timestr, header-&gt;ts.tv_usec, header-&gt;len);
  </code></pre>
  
  <p>Is it a typo?</p>
  
  <p>It seems <code>%.6d</code> is the same as <code>%6d</code>.</p>