title: sort -n does not work
body: <p>I have a file and I want it alphabetically sorted:</p>
  
  <pre><code>cat file
  peptide9
  peptide89
  peptide99
  peptide79
  peptide4
  peptide58
  peptide990
  </code></pre>
  
  <p>and when I use </p>
  
  <pre><code>cat file | sort -n
  </code></pre>
  
  <p>the result is:</p>
  
  <pre><code>peptide4
  peptide58
  peptide79
  peptide89
  peptide9
  peptide99
  peptide990
  </code></pre>
  
  <p>I tried different options of sort, but the result is always the same!<br>
  The output I want is</p>
  
  <pre><code>peptide4
  peptide9
  peptide58
  peptide79
  peptide89
  peptide99
  peptide990
  </code></pre>