title: Print only values smaller than certain threshold in bash
body: <p>I have a file with more than 10000 lines like this, mostly numbers and some strings;</p>
  
  <p>-40</p>
  
  <p>-50</p>
  
  <p>stringA</p>
  
  <p>100</p>
  
  <p>20</p>
  
  <p>-200</p>
  
  <p>...</p>
  
  <p>I would like to write a bash (or other) script that reading this file only outputs numbers (no strings) and only those values smaller than zero (or some other predefined number). How can this be done?</p>
  
  <p>In this case the output (sorted) would be</p>
  
  <p>-40</p>
  
  <p>-50</p>
  
  <p>-200</p>
  
  <p>...</p>