you could try one fo these
http://blog.amodernfable.com/2006/11/12/file-upload-content-types-on-ruby-on-rails-one-liner/ http://www.db75.com/new_blog/?p=289
These two pages don’t deal with determining the filetype for application-octet stream files, the content type just isn’t passed in on upload (probably because you’re using a Flash uploader). You can use mimetype_fu to determine the filetype, it works perfectly.
Best regards
Peter De Berdt