title: How to invert a grep expression
body: <p>The following grep expression successfully lists all the .exe and .html files in the current directory and sub directories.  </p>
  
  <pre><code>ls -R |grep -E .*[\.exe]$\|.*[\.html]$  
  </code></pre>
  
  <p>How do I invert this result to list those that aren't a .html or .exe instead. (That is, <code>!=</code>.)</p>