app.rb

require 'rubygems'
require 'sinatra'

get '/' do
  "Hello and Goodbye"
end

get '/hi' do
  "Hello World! :)"
end

get '/bye' do
  "Goodbye World! :("
end

config.ru

require 'rubygems'
require 'sinatra'

require 'app'
run Sinatra::Application

error.txt

Boot Error

Something went wrong while loading config.ru

LoadError: no such file to load -- app

<internal:lib/rubygems/custom_require>:29:in `require'
<internal:lib/rubygems/custom_require>:29:in `require'
config.ru:4:in `block in inner_app'
/usr/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:51:in `instance_eval'
/usr/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:51:in `initialize'
config.ru:1:in `new'
config.ru:1:in `inner_app'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/loader.rb:112:in `eval'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/loader.rb:112:in `inner_app'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/loader.rb:102:in `assemble_app'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/loader.rb:86:in `proceed_as_child'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/loader.rb:31:in `call!'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/loader.rb:18:in `call'
/usr/lib/ruby/gems/1.9.1/gems/shotgun-0.9/lib/shotgun/favicon.rb:12:in `call'
/usr/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/builder.rb:134:in `call'
/usr/lib/ruby/gems/1.9.1/gems/rack-1.3.1/lib/rack/handler/webrick.rb:59:in `service'
/usr/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
/usr/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
/usr/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'

Gemfile

source :rubygems
gem "sinatra", "1.2.6"
gem "shotgun", "0.9"

shotgun_run.txt

$ ls
app.rb  config.ru  Gemfile  Gemfile.lock  README.md

$ shotgun 
== Shotgun/WEBrick on http://127.0.0.1:9393/
[2011-07-20 11:49:33] INFO  WEBrick 1.3.1
[2011-07-20 11:49:33] INFO  ruby 1.9.2 (2011-07-09) [i686-linux]
[2011-07-20 11:49:33] INFO  WEBrick::HTTPServer#start: pid=11300 port=9393