title: Changing all occurrences in a folder
body: <p>I need to do a regex find and replace on all the files in a folder (and its subfolders). What would be the linux shell command to do that?</p>
  
  <p>For example, I want to run this over all the files and overwrite the old file with the new, replaced text.</p>
  
  <pre><code>sed 's/old text/new text/g' 
  </code></pre>