title: Count and display size of incoming stdin (count lines)
body: <p>Is there a program that would result in output like "wc -l" but that would update counter on more data.</p>
  
  <p>Here is what I want it for:</p>
  
  <pre><code>tail -f log/production.log | grep POST | wc -l
  </code></pre>
  
  <p>But wc -l should be changed for something.</p>