module ActionController::Head

def head(status, options = {})

render
return head(:bad_request) unless valid_request?
return head(:method_not_allowed) unless request.post?

It can also be used to return exceptional conditions:

head :created, :location => person_path(@person)

significant headers:
This allows you to easily return a response that consists only of
argument is interpreted to be a hash of header names and values.
Return a response that has no content (merely headers). The options 
def head(status, options = {})
  options, status = status, nil if status.is_a?(Hash)
  status ||= options.delete(:status) || :ok
  location = options.delete(:location)
  options.each do |key, value|
    headers[key.to_s.dasherize.split(/-/).map { |v| v.capitalize }.join("-")] = value.to_s
  end
  self.status = status
  self.location = url_for(location) if location
  self.content_type = Mime[formats.first]
  self.response_body = " "
end