title: How to check if username is valid on a ssh server
body: <p>How can I check if a username exists at a ssh server address using command line tools? For example, I would love to type,</p>
  
  <pre><code>isvaliduser [username] [ssh_server]
  result: True
  </code></pre>
  
  <p>where <code>isvaliduser</code> is some magical function that tests whether a user with name <code>username</code> exists at <code>ssh_server</code>. But is this feasible? </p>
  
  <p><strong>My specific application:</strong> The remote server I need to access has a dynamic IP (I can't use a Dynamic DNS service). I can come up with a list of server addresses that contains my target address, but I need a way to figure out which one is mine. I thought one way of doing this would be to test if any of the addresses have the user <code>myusername</code>. But if you have another suggestion for solving my particular problem, I would be happy to hear it.</p>