class Rails::Rack::LogTailer

def call(env)
  response = @app.call(env)
  tail!
  response
end

def initialize(app, log = nil)
  @app = app
  path = Pathname.new(log || "#{::File.expand_path(Rails.root)}/log/#{Rails.env}.log").cleanpath
  @cursor = @file = nil
  if ::File.exists?(path)
    @cursor = ::File.size(path)
    @file = ::File.open(path, 'r')
  end
end

def tail!
  return unless @cursor
  @file.seek @cursor
  unless @file.eof?
    contents = @file.read
    @cursor = @file.tell
    $stdout.print contents
  end
end