title: How to test if command line argument is entered?
body: <p>For my script, I'm getting an argument from user input on the command line, and I want to make sure the user doesn't forget to input the argument. So basically, I want to make my script do something like this:</p>
  
  <pre><code>on run argv
      if (item 1 of argv exists) then
          return "defined"
      else
          return "undefined"
      end if
  end run
  </code></pre>
  
  <p>Right now the part that says (item 1 of argv exists) does not work, but I hope someone can help me out. Thanks!</p>