title: How to check for a running process with Ruby?
body: <p>I use a scheduler (Rufus scheduler) to launch a process called "ar_sendmail" (from ARmailer), every minute.</p>
  
  <p>The process should NOT be launched when there is already such a process running in order not to eat up memory.</p>
  
  <p>How do I check to see if this process is already running? What goes after the <code>unless</code> below?</p>
  
  <pre><code>scheduler = Rufus::Scheduler.start_new
  
    scheduler.every '1m' do
  
      unless #[what goes here?]
        fork { exec "ar_sendmail -o" }
        Process.wait
      end
  
    end
  
  end
  </code></pre>