title: HTTP Range header
body: <p>I was reading <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35" rel="noreferrer">http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35</a>
  and trying to figure out how to continue a file download.</p>
  
  <p>For example, suppose a file is of length 100 bytes and I have all the 100 bytes. However, I don't know what the expected file size should be, so I ask for the file and specify a Range header that looks like this:</p>
  
  <pre><code>Range: bytes=100-
  </code></pre>
  
  <p>Is this a valid Range request?</p>