URI.join does not work quite the same way as File.join in Ruby. The aim of URI.join is more to calculate a relative path (as a browser would) than to simply concatenate path elements cleanly. The irb output below demonstrates this:

`

irb> require 'uri' #=> true
irb> host = 'http://www.example.com' #=> "http://www.example.com"
irb> prefix = 'prefix' #=> "prefix"
irb> file = 'file.html' #=> "file.html"
irb> URI.join(host, prefix, file).to_s #=> "http://www.example.com/file.html"
irb> URI.join(host, prefix+ '/', file).to_s #=> "http://www.example.com/prefix/file.html"

`