title: checksum remote file
body: <p>Is there a way to get a program I can run via the command line that would do a checksum of a remote file? For instance get a checksum of <a href="https://stackoverflow.com/opensearch.xml">https://stackoverflow.com/opensearch.xml</a></p>
  
  <p>I want to be able get an update of when a new rss/xml entry is available. I was thinking I could do a checksum of a file every once in a while and if it is different then there must be an update. I'm looking to write a shell script that checks new rss/xml data.</p>