title: Add a big buffer to a pipe between two commands
body: <p>Given a bash command line of the form</p>
  
  <pre><code>commandA | commandB
  </code></pre>
  
  <p>I want to add a buffer of size ~1MB that sits between <code>commandA</code> and <code>commandB</code>.
  I would expect to be able to do this with something of the form</p>
  
  <pre><code>commandA | BUFFER | commandB
  </code></pre>
  
  <p>but what is the command to use for <code>BUFFER</code>?</p>
  
  <p>Remark: I want to do this in order to decouple the two commands to make them parallelize better. The problem is that <code>commandB</code> processes data in large chunks, which currently means that <code>commandA</code> blocks until <code>commandB</code> is done with a chunk. So everything runs sequentially :-(</p>