title: Add an answer to a command in shell script
body: <p>I am wondering how to add an answer to a command in a shell script. I know this isn't very clear, as I don't know how to describe it. For example:</p>
  
  <pre><code>$&gt; su
  $&gt; Password: &lt;automatically_fill_in_the_password_here&gt;
  </code></pre>
  
  <p>How would I automatically fill in the password?</p>