title: Shell -e command
body: <p>I came across <a href="https://gist.github.com/erikh/2260182" rel="nofollow">this shell script</a> for OSX and I don't understand the following:</p>
  
  <p><code>[ -e ~/Library/Application\ Support/Dock/*.db ]</code> on line 191?</p>
  
  <p>What is that command doing? I've also seen things like <code>[ -r "$file" ]</code>. I don't completely understand this syntax.</p>