shotgunを使えば、Sinatra開発にサーバーの再起動はもう無用

Source file reloading was removed in the 0.9.2 due to excess complexity.

For reloading Sinatra you can use shotgun, Rack::Reloader, or Sinatra::Reloader.

Sinatra: Frequently Asked Questions

$ sudo gem install shotgun
$ shotgun myapp.rb

shotgun使えば、変更する度にサーバーを再起動させる必要なくなります。