title: Using awk to search for lines that have a number of digits
body: <p>Here is file1</p>
  
  <pre><code>200
  201
  202
  203
  204
  205
  2001
  2002
  2003
  2004
  2005
  </code></pre>
  
  <p>Is there an awk oneliner that finds only lines with three digits in the the first field? </p>