title: How to read a text file into an environment variable?
body: <p>I have a one line text file (it will always be just one line). For example:</p>
  
  <p>helloworld.txt contains <em>"hello world"</em></p>
  
  <p>I want to read this into an environment variable via the command prompt.</p>
  
  <p>so <code>Set MyVar=somehow</code> reads <em>helloworld.txt</em></p>
  
  <p>Does anyone know how to do this?</p>