Ruby Best Practices

Working with HTTP and FTP (open-uri)

Like most other modern programming languages, Ruby ships with libraries for working with some of the most common network protocols, including FTP and HTTP. However, the Net::FTP and Net::HTTP libraries are designed primarily for heavy lifting at the low level. They are great for this purpose, but they leave something to be desired for when all that is needed is to grab a remote file or do some basic web scraping. This is where open-uri shines.

The way open-uri works is by patching Kernel#open to accept URIs. This means we can directly open remote files and work with them. For example, here’s how we’d print out Ruby’s license using open-uri:

require "open-uri"

puts open("http://www.ruby-lang.org/en/LICENSE.txt").read #=>

"Ruby is copyrighted free software by Yukihiro Matsumoto <[e-mail]>.
You can redistribute it and/or modify it under either the terms of the GPL
(see COPYING.txt file), or the conditions below: ..."

If we encounter an HTTP error, an OpenURI::HTTPError will be raised, including the relevant error code:

>> open("http://majesticseacreature.com/a_totally_missing_document") OpenURI::HTTPError: 404 Not Found from /usr/local/lib/ruby/1.8/open-uri.rb:287:in 'open_http' from /usr/local/lib/ruby/1.8/open-uri.rb:626:in 'buffer_open' from /usr/local/lib/ruby/1.8/open-uri.rb:164:in 'open_loop' from /usr/local/lib/ruby/1.8/open-uri.rb:162:in 'catch' from /usr/local/lib/ruby/1.8/open-uri.rb:162:in 'open_loop' from /usr/local/lib/ruby/1.8/open-uri.rb:132:in ...