title: Why do seemingly empty files and strings produce md5sums?
body: <p>Consider the following:</p>
  
  <pre><code>% md5sum /dev/null
  d41d8cd98f00b204e9800998ecf8427e  /dev/null
  % touch empty; md5sum empty
  d41d8cd98f00b204e9800998ecf8427e  empty
  % echo '' | md5sum
  68b329da9893e34099c7d8ad5cb9c940  -
  % perl -e 'print chr(0)' | md5sum
  93b885adfe0da089cdf634904fd59f71  -
  % md5sum ''
  md5sum: : No such file or directory
  </code></pre>
  
  <p>First of all, I'm surprised by the output of all these commands. If anything, I would expect the sum to be the same for all of them. </p>