title: How do I check if a variable is set in zsh?
body: <p>What is the canonical / idiomatic way to test if a variable has been set in zsh?</p>
  
  <pre><code>if ....something.... ; then
      print "Sweet, that variable is defined"
  else
      print "That variable is not defined"
  fi
  </code></pre>
  
  <p>Here's <a href="https://stackoverflow.com/a/13864829/893113">the SO answer for bash</a>.</p>