title: Basic stream/sed? bash script, perform substring on each line
body: <p>I know this is basic, but I couldn't find the simplest way to iterate through a file with hundreds of lines and extract a substring.</p>
  
  <p>If I have a file:</p>
  
  <pre><code>ABCY uuuu
  UNUY uuuu
  
  ...
  </code></pre>
  
  <p>I want to end up with:</p>
  
  <pre><code>uuuu
  uuuu
  ....
  </code></pre>
  
  <p>Ideally do a substring</p>
  
  <p>{5} detect at character 5 and output that</p>