title: Regex for digits in Unix find command
body: <p>I have this command:</p>
  
  <pre><code>find reports/ -type f -mtime +90 -regex ".*\.\(csv\|sql\|txt\|xls\|zip\)"
  </code></pre>
  
  <p>And I need to beef it up so the part before the file extensions matches a <code>YYYY/MM/DD</code> pattern, like so:</p>
  
  <pre><code>reports/2010/10/10/23.txt
  reports/2010/10/10/23.xls
  reports/2010/10/10/26.csv
  reports/2010/10/10/26.sql
  reports/2010/10/10/26.txt
  reports/2010/10/10/26.xls
  reports/2010/10/10/27.csv
  </code></pre>
  
  <p>But I'm failing to get any permutation of <code>\d</code> and parens escaping to work.</p>
  
  <p><em>UPDATE</em>: here's what worked for me based on the accepted answer below:</p>
  
  <pre><code>find reports/ -type f -mtime +90 -regex "reports/201[01]/\([1-9]\|1[012]\)/\([1-9]\|[12][0-9]\|3[01]\)/.*\.\(csv\|sql\|txt\|xls\|zip\)"
  </code></pre>