Saving generated xml to an S3 store

Here's a problem that come up recently, how to generate an xml document and save it to S3 without creating an intermediate local file. I'm using Nokogiri's XML builder and the fog gem:

require 'fog'
require 'nokogiri'

# build the xml
builder = Nokogiri::XML::Builder.new do |xml|
  xml.root do
    xml.foo 'bar'
  end
end

# log in to S3 and save it
storage = Fog::Storage.new :provider => 'AWS',
  :aws_access_key_id => ENV['AMAZON_ACCESS_KEY_ID'],
  :aws_secret_access_key => ENV['AMAZON_SECRET_ACCESS_KEY']

dir = storage.directories.get 'my_bucket'
dir.files.create :key => 'huge.xml', :body   => builder.to_xml

Notice the Amazon credentials are in environmental variables rather than coded in. This will protect you from accidentally giving them away (leaving them in a public git repo for example)