title: My if statement doesn't work with Bash
body: <p>I am getting this error:</p>
  
  <pre><code>[[: command not found
  </code></pre>
  
  <p>Here is my code:</p>
  
  <pre><code>#!/usr/bin/env bash
  
  IS_PYSTACHE_INSTALLED=$(pip list --format=columns | grep "pystache ")
  if [[ ! -z "${IS_PYSTACHE_INSTALLED}" ]]; then
      echo " &gt; Installing pystache"
      pip install pystache
  else
      echo " &gt; Pystache is already installed"
  fi
  </code></pre>
  
  <p>What am I doing wrong?</p>