rack

$ sudo gem install rack

hello.rb

require 'rubygems'
require 'rack'

class Hello
  def call(env)
    [200, {"Content-Type" => 'text/plain'},["Hello World!"]]
  end
end

hello.ru

require 'hello'
run Hello.new

実行（rack up）

$rackup hello.ru

http://localhost:9292/ へアクセス→ウマー

RequestとResponse

hello.rb

require 'rubygems'
require 'rack'

class Hello
  def call(env)
    req = Rack::Request.new(env)

    res = Rack::Response.new()
    res.status = 200
    res["Content-Type"] = "text/plain"
    res.write( req.params.map{ |k, v| "#{k}=#{v}" }.join("\n") )
    res.finish
  end
end

rack upして http://localhost:9292/?hoge=1&fuga=2 へアクセス→ウマー

なるほど…。