title: Rails route to access files saved to tmp directory
body: <p>In my background worker I'm creating a pdf and saving it to the <code>tmp</code> directory with:</p>
  
  <pre><code>save_path = Rails.root.join('tmp', unique_report_name)
  File.open(save_path, 'wb') do |file|
    file &lt;&lt; pdf
  end
  </code></pre>
  
  <p>I then try to open the pdf in a new window and get <code>ActionController::RoutingError (No route matches [GET]</code> errors.</p>
  
  <p>I've tried copying what they do with CarrierWave (I'm <strong>not</strong> using CarrierWave) by using the below in <code>config.ru</code>:</p>
  
  <p><code>use Rack::Static, :urls =&gt; ['/tmp'], :root =&gt; 'tmp'</code></p>
  
  <p>but I get the error <code>File not found: /tmp/my_file_name.pdf</code> even though the file does indeed exist in the location.</p>