title: Take only the lines with numbers with egrep
body: <p>i have a file where lines have numbers with characters,only characters and only numbers. I would like to choose the lines with only numbers. I tried <code>egrep '[^[:alpha:]]' filename</code> but i take also lines with chars. Any idea?</p>
  
  <pre><code>AQ
  Feb 9, 1999
  11:45
  45
  </code></pre>
  
  <p>And i want only</p>
  
  <pre><code>45
  </code></pre>