title: what does [[ -s mean in linux shell
body: <p>I found this command. I understand the source reloads the bash profile and fixed permissions for Ruby permissions needed on Ubuntu. But what does the part before &amp;&amp; mean?</p>
  
  <pre><code>[[ -s "$HOME/.rvm/scripts/rvm" ]] &amp;&amp; source "$HOME/.rvm/scripts/rvm" 
  </code></pre>