title: UNIX 'ls' command - wildcard 'OR' operator
body: <p>I have a directory with timestamped files in the format:</p>
  
  <pre><code>processAlpha20120618.txt
  processAlpha20120619.txt
  processAlpha20120620.txt
  processBeta20120618.txt
  processBeta20120619.txt
  processBeta20120620.txt
  ... etc.
  </code></pre>
  
  <p>I want a list of these for specific dates. Something like this:</p>
  
  <pre><code>ls -l *201206[19|20|21]*
  </code></pre>
  
  <p>Obviously the above doesn't work, but you can see what I was trying to achieve. I want to match anything where the string "201206" is followed by either "19", "20" or "21".</p>
  
  <p>I know that this is possible using <strong>grep</strong> or <strong>find</strong>, I just wondered if it could be done using <strong>ls</strong>.</p>