title: Is there a list of 'if' switches anywhere?
body: <p>Is there a list of all the <code>if</code> switches for use in Bash scripting? Sometimes I see someone using it and I wonder what the switch they're using actually does.</p>
  <p>An example is the <code>-z</code> in this one. I know how to use it, but I don't know where it was derived from.</p>
  <pre><code>if [ -z &quot;$BASH_VERSION&quot; ]; then
      echo -e &quot;Error: this script requires the BASH shell!&quot;
      exit 1
  fi
  </code></pre>
  <p>Any references, guides, posts, answers would be appreciated.</p>