Force browser to download file instead of opening it

I would like to download http://foobar.com/song.mp3 as song.mp3, instead of having Chrome open it in its native <audio> player in the browser.

How can I accmplish this开发者_高级运维?

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You just need to make sure to send these headers:

Content-Disposition: attachment; filename=song.mp3;
Content-Type: application/octet-stream
Content-Transfer-Encoding: binary

The send_file method does it for you:

get '/:file' do |file|
  file = File.join('/some/path', file)
  send_file(file, :disposition => 'attachment', :filename => File.basename(file))
end