title: How to test multiple variables for empty string
body: <p>I want to test multiple variables to see if they are empty. So I did the following:</p>
  
  <pre><code>if [ test -z "$VAR1" ] || [ test -z "$VAR2" ]
  then
     echo "Empty!"
  fi
  </code></pre>
  
  <p>However, it doesn't work. The output is:</p>
  
  <pre><code>[: -z: binary operator expected
  [: -z: binary operator expected
  </code></pre>
  
  <p>What have I done wrong? The code above works fine if I leave out the <strong>OR</strong> (||) condition.</p>