File uploading in Rails 3

Can anyone give me a link to a tutorial or an example on how to do image
uploading in Rail 3 without use of paperclip, carrierwave or any other
gems? Found some like
http://www.tutorialspoint.com/ruby-on-rails/rails-file-uploading.htm but
they don’t work, like how calling .read from upload or
.original_filename both don’t work. Thanks