title: find with -regex flag ti match files
body: <p>under /tmp directory I have the following files </p>
  
  <pre><code> file1
   file2
  </code></pre>
  
  <p>when I run the following find command with -regex , find command not match the files
  why?</p>
  
  <pre><code>  find /tmp  -regex '/file(\d{1,3})/'
  </code></pre>