How can I find out the size of this file?

Question

Ruby on Rails

Good day!
The whole day I can not get through to the size of this file. I understand that, apparently, I’m not knocking correctly, so I decided to ask knowledgeable people:
There is a method that generates and returns a link to a PDF file, which, in turn, is stored on Amazon. When you click on the link, the file itself opens (does not download):

def self.get_pdf_url(manual, lesson = nil)
    link = DOMAIN + "/s/#{ENV['SCREENSTEPS_LIVE_SITE_ID']}/m/" + manual + '/'
    link += 'pdf'
  end

The problem is the following:
find out the size of a PDF file without downloading based on this method and, for example, display it right next to the link. Something like this:

= link_to model_name.get_pdf_url(some_option) do
  .name= link_to_pdf_name
  .size= pdf_size

And then a completely logical question immediately arises (given my not deep knowledge of RoR): is it really possible to do this at all?
I would be very grateful for any clarifications or kicks!
Thank you very much in advance)

Answer 1

Make a HEAD request to the file and read the content-length header
But it’s not clear at all:
if pdf is generated on the same host and uploaded to Amazon, then why not take the size from tmp or where the file is written before downloading.