Collect records and save them as a list of URLs from within the rails console.

records_to_urls.rb

target = URI.parse("http://www.your-host.org")
petitions = Petition.select([:id, :slug]).limit(10)
urls = petitions.map { |p| app.url_for(:subdomain=>"www", :action=>"show", :controller=>"petitions", :host => target.host, :id => p.slug) }
File.open('urls.txt') { |io| urls.each { |u| io.puts u } }

Rails.app.routes.url_helpers.petition_url(petition) might be more correct