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+# Sinatra
+
+[![Gem Version](https://badge.fury.io/rb/sinatra.svg)](https://badge.fury.io/rb/sinatra)
+[![Build Status](https://secure.travis-ci.org/sinatra/sinatra.svg)](https://travis-ci.org/sinatra/sinatra)
+[![SemVer](https://api.dependabot.com/badges/compatibility_score?dependency-name=sinatra&package-manager=bundler&version-scheme=semver)](https://dependabot.com/compatibility-score.html?dependency-name=sinatra&package-manager=bundler&version-scheme=semver)
+
+Sinatra is a [DSL](https://en.wikipedia.org/wiki/Domain-specific_language) for
+quickly creating web applications in Ruby with minimal effort:
+
+```ruby
+# myapp.rb
+require 'sinatra'
+
+get '/' do
+  'Hello world!'
+end
+```
+
+Install the gem:
+
+```shell
+gem install sinatra
+```
+
+And run with:
+
+```shell
+ruby myapp.rb
+```
+
+View at: [http://localhost:4567](http://localhost:4567)
+
+The code you changed will not take effect until you restart the server.
+Please restart the server every time you change or use
+[sinatra/reloader](http://www.sinatrarb.com/contrib/reloader).
+
+It is recommended to also run `gem install puma`, which Sinatra will
+pick up if available.
+
+## Table of Contents
+
+* [Sinatra](#sinatra)
+    * [Table of Contents](#table-of-contents)
+    * [Routes](#routes)
+    * [Conditions](#conditions)
+    * [Return Values](#return-values)
+    * [Custom Route Matchers](#custom-route-matchers)
+    * [Static Files](#static-files)
+    * [Views / Templates](#views--templates)
+        * [Literal Templates](#literal-templates)
+        * [Available Template Languages](#available-template-languages)
+            * [Haml Templates](#haml-templates)
+            * [Erb Templates](#erb-templates)
+            * [Builder Templates](#builder-templates)
+            * [Nokogiri Templates](#nokogiri-templates)
+            * [Sass Templates](#sass-templates)
+            * [SCSS Templates](#scss-templates)
+            * [Less Templates](#less-templates)
+            * [Liquid Templates](#liquid-templates)
+            * [Markdown Templates](#markdown-templates)
+            * [Textile Templates](#textile-templates)
+            * [RDoc Templates](#rdoc-templates)
+            * [AsciiDoc Templates](#asciidoc-templates)
+            * [Radius Templates](#radius-templates)
+            * [Markaby Templates](#markaby-templates)
+            * [RABL Templates](#rabl-templates)
+            * [Slim Templates](#slim-templates)
+            * [Creole Templates](#creole-templates)
+            * [MediaWiki Templates](#mediawiki-templates)
+            * [CoffeeScript Templates](#coffeescript-templates)
+            * [Stylus Templates](#stylus-templates)
+            * [Yajl Templates](#yajl-templates)
+            * [WLang Templates](#wlang-templates)
+        * [Accessing Variables in Templates](#accessing-variables-in-templates)
+        * [Templates with `yield` and nested layouts](#templates-with-yield-and-nested-layouts)
+        * [Inline Templates](#inline-templates)
+        * [Named Templates](#named-templates)
+        * [Associating File Extensions](#associating-file-extensions)
+        * [Adding Your Own Template Engine](#adding-your-own-template-engine)
+        * [Using Custom Logic for Template Lookup](#using-custom-logic-for-template-lookup)
+    * [Filters](#filters)
+    * [Helpers](#helpers)
+        * [Using Sessions](#using-sessions)
+            * [Session Secret Security](#session-secret-security)
+            * [Session Config](#session-config)
+            * [Choosing Your Own Session Middleware](#choosing-your-own-session-middleware)
+        * [Halting](#halting)
+        * [Passing](#passing)
+        * [Triggering Another Route](#triggering-another-route)
+        * [Setting Body, Status Code and Headers](#setting-body-status-code-and-headers)
+        * [Streaming Responses](#streaming-responses)
+        * [Logging](#logging)
+        * [Mime Types](#mime-types)
+        * [Generating URLs](#generating-urls)
+        * [Browser Redirect](#browser-redirect)
+        * [Cache Control](#cache-control)
+        * [Sending Files](#sending-files)
+        * [Accessing the Request Object](#accessing-the-request-object)
+        * [Attachments](#attachments)
+        * [Dealing with Date and Time](#dealing-with-date-and-time)
+        * [Looking Up Template Files](#looking-up-template-files)
+    * [Configuration](#configuration)
+        * [Configuring attack protection](#configuring-attack-protection)
+        * [Available Settings](#available-settings)
+    * [Environments](#environments)
+    * [Error Handling](#error-handling)
+        * [Not Found](#not-found)
+        * [Error](#error)
+    * [Rack Middleware](#rack-middleware)
+    * [Testing](#testing)
+    * [Sinatra::Base - Middleware, Libraries, and Modular Apps](#sinatrabase---middleware-libraries-and-modular-apps)
+        * [Modular vs. Classic Style](#modular-vs-classic-style)
+        * [Serving a Modular Application](#serving-a-modular-application)
+        * [Using a Classic Style Application with a config.ru](#using-a-classic-style-application-with-a-configru)
+        * [When to use a config.ru?](#when-to-use-a-configru)
+        * [Using Sinatra as Middleware](#using-sinatra-as-middleware)
+        * [Dynamic Application Creation](#dynamic-application-creation)
+    * [Scopes and Binding](#scopes-and-binding)
+        * [Application/Class Scope](#applicationclass-scope)
+        * [Request/Instance Scope](#requestinstance-scope)
+        * [Delegation Scope](#delegation-scope)
+    * [Command Line](#command-line)
+        * [Multi-threading](#multi-threading)
+    * [Requirement](#requirement)
+    * [The Bleeding Edge](#the-bleeding-edge)
+        * [With Bundler](#with-bundler)
+    * [Versioning](#versioning)
+    * [Further Reading](#further-reading)
+
+## Routes
+
+In Sinatra, a route is an HTTP method paired with a URL-matching pattern.
+Each route is associated with a block:
+
+```ruby
+get '/' do
+  .. show something ..
+end
+
+post '/' do
+  .. create something ..
+end
+
+put '/' do
+  .. replace something ..
+end
+
+patch '/' do
+  .. modify something ..
+end
+
+delete '/' do
+  .. annihilate something ..
+end
+
+options '/' do
+  .. appease something ..
+end
+
+link '/' do
+  .. affiliate something ..
+end
+
+unlink '/' do
+  .. separate something ..
+end
+```
+
+Routes are matched in the order they are defined. The first route that
+matches the request is invoked.
+
+Routes with trailing slashes are different from the ones without:
+
+```ruby
+get '/foo' do
+  # Does not match "GET /foo/"
+end
+```
+
+Route patterns may include named parameters, accessible via the
+`params` hash:
+
+```ruby
+get '/hello/:name' do
+  # matches "GET /hello/foo" and "GET /hello/bar"
+  # params['name'] is 'foo' or 'bar'
+  "Hello #{params['name']}!"
+end
+```
+
+You can also access named parameters via block parameters:
+
+```ruby
+get '/hello/:name' do |n|
+  # matches "GET /hello/foo" and "GET /hello/bar"
+  # params['name'] is 'foo' or 'bar'
+  # n stores params['name']
+  "Hello #{n}!"
+end
+```
+
+Route patterns may also include splat (or wildcard) parameters, accessible
+via the `params['splat']` array:
+
+```ruby
+get '/say/*/to/*' do
+  # matches /say/hello/to/world
+  params['splat'] # => ["hello", "world"]
+end
+
+get '/download/*.*' do
+  # matches /download/path/to/file.xml
+  params['splat'] # => ["path/to/file", "xml"]
+end
+```
+
+Or with block parameters:
+
+```ruby
+get '/download/*.*' do |path, ext|
+  [path, ext] # => ["path/to/file", "xml"]
+end
+```
+
+Route matching with Regular Expressions:
+
+```ruby
+get /\/hello\/([\w]+)/ do
+  "Hello, #{params['captures'].first}!"
+end
+```
+
+Or with a block parameter:
+
+```ruby
+get %r{/hello/([\w]+)} do |c|
+  # Matches "GET /meta/hello/world", "GET /hello/world/1234" etc.
+  "Hello, #{c}!"
+end
+```
+
+Route patterns may have optional parameters:
+
+```ruby
+get '/posts/:format?' do
+  # matches "GET /posts/" and any extension "GET /posts/json", "GET /posts/xml" etc
+end
+```
+
+Routes may also utilize query parameters:
+
+```ruby
+get '/posts' do
+  # matches "GET /posts?title=foo&author=bar"
+  title = params['title']
+  author = params['author']
+  # uses title and author variables; query is optional to the /posts route
+end
+```
+
+By the way, unless you disable the path traversal attack protection (see
+[below](#configuring-attack-protection)), the request path might be modified before
+matching against your routes.
+
+You may customize the [Mustermann](https://github.com/sinatra/mustermann#readme)
+options used for a given route by passing in a `:mustermann_opts` hash:
+
+```ruby
+get '\A/posts\z', :mustermann_opts => { :type => :regexp, :check_anchors => false } do
+  # matches /posts exactly, with explicit anchoring
+  "If you match an anchored pattern clap your hands!"
+end
+```
+
+It looks like a [condition](#conditions), but it isn't one! These options will
+be merged into the global `:mustermann_opts` hash described
+[below](#available-settings).
+
+## Conditions
+
+Routes may include a variety of matching conditions, such as the user agent:
+
+```ruby
+get '/foo', :agent => /Songbird (\d\.\d)[\d\/]*?/ do
+  "You're using Songbird version #{params['agent'][0]}"
+end
+
+get '/foo' do
+  # Matches non-songbird browsers
+end
+```
+
+Other available conditions are `host_name` and `provides`:
+
+```ruby
+get '/', :host_name => /^admin\./ do
+  "Admin Area, Access denied!"
+end
+
+get '/', :provides => 'html' do
+  haml :index
+end
+
+get '/', :provides => ['rss', 'atom', 'xml'] do
+  builder :feed
+end
+```
+`provides` searches the request's Accept header.
+
+You can easily define your own conditions:
+
+```ruby
+set(:probability) { |value| condition { rand <= value } }
+
+get '/win_a_car', :probability => 0.1 do
+  "You won!"
+end
+
+get '/win_a_car' do
+  "Sorry, you lost."
+end
+```
+
+For a condition that takes multiple values use a splat:
+
+```ruby
+set(:auth) do |*roles|   # <- notice the splat here
+  condition do
+    unless logged_in? && roles.any? {|role| current_user.in_role? role }
+      redirect "/login/", 303
+    end
+  end
+end
+
+get "/my/account/", :auth => [:user, :admin] do
+  "Your Account Details"
+end
+
+get "/only/admin/", :auth => :admin do
+  "Only admins are allowed here!"
+end
+```
+
+## Return Values
+
+The return value of a route block determines at least the response body
+passed on to the HTTP client or at least the next middleware in the
+Rack stack. Most commonly, this is a string, as in the above examples.
+But other values are also accepted.
+
+You can return an object that would either be a valid Rack response, Rack
+body object or HTTP status code:
+
+* An Array with three elements: `[status (Integer), headers (Hash), response
+  body (responds to #each)]`
+* An Array with two elements: `[status (Integer), response body (responds to
+  #each)]`
+* An object that responds to `#each` and passes nothing but strings to
+  the given block
+* A Integer representing the status code
+
+That way we can, for instance, easily implement a streaming example:
+
+```ruby
+class Stream
+  def each
+    100.times { |i| yield "#{i}\n" }
+  end
+end
+
+get('/') { Stream.new }
+```
+
+You can also use the `stream` helper method ([described below](#streaming-responses)) to reduce
+boilerplate and embed the streaming logic in the route.
+
+## Custom Route Matchers
+
+As shown above, Sinatra ships with built-in support for using String
+patterns and regular expressions as route matches. However, it does not
+stop there. You can easily define your own matchers:
+
+```ruby
+class AllButPattern
+  Match = Struct.new(:captures)
+
+  def initialize(except)
+    @except   = except
+    @captures = Match.new([])
+  end
+
+  def match(str)
+    @captures unless @except === str
+  end
+end
+
+def all_but(pattern)
+  AllButPattern.new(pattern)
+end
+
+get all_but("/index") do
+  # ...
+end
+```
+
+Note that the above example might be over-engineered, as it can also be
+expressed as:
+
+```ruby
+get // do
+  pass if request.path_info == "/index"
+  # ...
+end
+```
+
+Or, using negative look ahead:
+
+```ruby
+get %r{(?!/index)} do
+  # ...
+end
+```
+
+## Static Files
+
+Static files are served from the `./public` directory. You can specify
+a different location by setting the `:public_folder` option:
+
+```ruby
+set :public_folder, __dir__ + '/static'
+```
+
+Note that the public directory name is not included in the URL. A file
+`./public/css/style.css` is made available as
+`http://example.com/css/style.css`.
+
+Use the `:static_cache_control` setting (see [below](#cache-control)) to add
+`Cache-Control` header info.
+
+## Views / Templates
+
+Each template language is exposed via its own rendering method. These
+methods simply return a string:
+
+```ruby
+get '/' do
+  erb :index
+end
+```
+
+This renders `views/index.erb`.
+
+Instead of a template name, you can also just pass in the template content
+directly:
+
+```ruby
+get '/' do
+  code = "<%= Time.now %>"
+  erb code
+end
+```
+
+Templates take a second argument, the options hash:
+
+```ruby
+get '/' do
+  erb :index, :layout => :post
+end
+```
+
+This will render `views/index.erb` embedded in the
+`views/post.erb` (default is `views/layout.erb`, if it exists).
+
+Any options not understood by Sinatra will be passed on to the template
+engine:
+
+```ruby
+get '/' do
+  haml :index, :format => :html5
+end
+```
+
+You can also set options per template language in general:
+
+```ruby
+set :haml, :format => :html5
+
+get '/' do
+  haml :index
+end
+```
+
+Options passed to the render method override options set via `set`.
+
+Available Options:
+
+<dl>
+  <dt>locals</dt>
+  <dd>
+    List of locals passed to the document. Handy with partials.
+    Example: <tt>erb "<%= foo %>", :locals => {:foo => "bar"}</tt>
+  </dd>
+
+  <dt>default_encoding</dt>
+  <dd>
+    String encoding to use if uncertain. Defaults to
+    <tt>settings.default_encoding</tt>.
+  </dd>
+
+  <dt>views</dt>
+  <dd>
+    Views folder to load templates from. Defaults to <tt>settings.views</tt>.
+  </dd>
+
+  <dt>layout</dt>
+  <dd>
+    Whether to use a layout (<tt>true</tt> or <tt>false</tt>). If it's a
+    Symbol, specifies what template to use. Example:
+    <tt>erb :index, :layout => !request.xhr?</tt>
+  </dd>
+
+  <dt>content_type</dt>
+  <dd>
+    Content-Type the template produces. Default depends on template language.
+  </dd>
+
+  <dt>scope</dt>
+  <dd>
+    Scope to render template under. Defaults to the application
+    instance. If you change this, instance variables and helper methods
+    will not be available.
+  </dd>
+
+  <dt>layout_engine</dt>
+  <dd>
+    Template engine to use for rendering the layout. Useful for
+    languages that do not support layouts otherwise. Defaults to the
+    engine used for the template. Example: <tt>set :rdoc, :layout_engine
+    => :erb</tt>
+  </dd>
+
+  <dt>layout_options</dt>
+  <dd>
+    Special options only used for rendering the layout. Example:
+    <tt>set :rdoc, :layout_options => { :views => 'views/layouts' }</tt>
+  </dd>
+</dl>
+
+Templates are assumed to be located directly under the `./views`
+directory. To use a different views directory:
+
+```ruby
+set :views, settings.root + '/templates'
+```
+
+
+One important thing to remember is that you always have to reference
+templates with symbols, even if they're in a subdirectory (in this case,
+use: `:'subdir/template'` or `'subdir/template'.to_sym`). You must use a
+symbol because otherwise rendering methods will render any strings
+passed to them directly.
+
+### Literal Templates
+
+```ruby
+get '/' do
+  haml '%div.title Hello World'
+end
+```
+
+Renders the template string. You can optionally specify `:path` and
+`:line` for a clearer backtrace if there is a filesystem path or line
+associated with that string:
+
+```ruby
+get '/' do
+  haml '%div.title Hello World', :path => 'examples/file.haml', :line => 3
+end
+```
+
+### Available Template Languages
+
+Some languages have multiple implementations. To specify what implementation
+to use (and to be thread-safe), you should simply require it first:
+
+```ruby
+require 'rdiscount' # or require 'bluecloth'
+get('/') { markdown :index }
+```
+
+#### Haml Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://haml.info/" title="haml">haml</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.haml</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>haml :index, :format => :html5</tt></td>
+  </tr>
+</table>
+
+#### Erb Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td>
+      <a href="https://github.com/jeremyevans/erubi" title="erubi">erubi</a>
+      or <a href="http://www.kuwata-lab.com/erubis/" title="erubis">erubis</a>
+      or erb (included in Ruby)
+    </td>
+  </tr>
+  <tr>
+    <td>File Extensions</td>
+    <td><tt>.erb</tt>, <tt>.rhtml</tt> or <tt>.erubi</tt> (Erubi only)
+ or <tt>.erubis</tt> (Erubis only)</td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>erb :index</tt></td>
+  </tr>
+</table>
+
+#### Builder Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td>
+      <a href="https://github.com/jimweirich/builder" title="builder">builder</a>
+    </td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.builder</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>builder { |xml| xml.em "hi" }</tt></td>
+  </tr>
+</table>
+
+It also takes a block for inline templates (see [example](#inline-templates)).
+
+#### Nokogiri Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://www.nokogiri.org/" title="nokogiri">nokogiri</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.nokogiri</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>nokogiri { |xml| xml.em "hi" }</tt></td>
+  </tr>
+</table>
+
+It also takes a block for inline templates (see [example](#inline-templates)).
+
+#### Sass Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://sass-lang.com/" title="sass">sass</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.sass</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>sass :stylesheet, :style => :expanded</tt></td>
+  </tr>
+</table>
+
+#### SCSS Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://sass-lang.com/" title="sass">sass</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.scss</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>scss :stylesheet, :style => :expanded</tt></td>
+  </tr>
+</table>
+
+#### Less Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://lesscss.org/" title="less">less</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.less</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>less :stylesheet</tt></td>
+  </tr>
+</table>
+
+#### Liquid Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://shopify.github.io/liquid/" title="liquid">liquid</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.liquid</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>liquid :index, :locals => { :key => 'value' }</tt></td>
+  </tr>
+</table>
+
+Since you cannot call Ruby methods (except for `yield`) from a Liquid
+template, you almost always want to pass locals to it.
+
+#### Markdown Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td>
+      Anyone of:
+        <a href="https://github.com/davidfstr/rdiscount" title="RDiscount">RDiscount</a>,
+        <a href="https://github.com/vmg/redcarpet" title="RedCarpet">RedCarpet</a>,
+        <a href="https://github.com/ged/bluecloth" title="BlueCloth">BlueCloth</a>,
+        <a href="https://kramdown.gettalong.org/" title="kramdown">kramdown</a>,
+        <a href="https://github.com/bhollis/maruku" title="maruku">maruku</a>
+        <a href="https://github.com/gjtorikian/commonmarker" title="commonmarker">commonmarker</a>
+        <a href="https://github.com/alphabetum/pandoc-ruby" title="pandoc">pandoc</a>
+    </td>
+  </tr>
+  <tr>
+    <td>File Extensions</td>
+    <td><tt>.markdown</tt>, <tt>.mkd</tt> and <tt>.md</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>markdown :index, :layout_engine => :erb</tt></td>
+  </tr>
+</table>
+
+It is not possible to call methods from Markdown, nor to pass locals to it.
+You therefore will usually use it in combination with another rendering
+engine:
+
+```ruby
+erb :overview, :locals => { :text => markdown(:introduction) }
+```
+
+Note that you may also call the `markdown` method from within other
+templates:
+
+```ruby
+%h1 Hello From Haml!
+%p= markdown(:greetings)
+```
+
+Since you cannot call Ruby from Markdown, you cannot use layouts written in
+Markdown. However, it is possible to use another rendering engine for the
+template than for the layout by passing the `:layout_engine` option.
+
+#### Textile Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://redcloth.org/" title="RedCloth">RedCloth</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.textile</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>textile :index, :layout_engine => :erb</tt></td>
+  </tr>
+</table>
+
+It is not possible to call methods from Textile, nor to pass locals to
+it. You therefore will usually use it in combination with another
+rendering engine:
+
+```ruby
+erb :overview, :locals => { :text => textile(:introduction) }
+```
+
+Note that you may also call the `textile` method from within other templates:
+
+```ruby
+%h1 Hello From Haml!
+%p= textile(:greetings)
+```
+
+Since you cannot call Ruby from Textile, you cannot use layouts written in
+Textile. However, it is possible to use another rendering engine for the
+template than for the layout by passing the `:layout_engine` option.
+
+#### RDoc Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://rdoc.sourceforge.net/" title="RDoc">RDoc</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.rdoc</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>rdoc :README, :layout_engine => :erb</tt></td>
+  </tr>
+</table>
+
+It is not possible to call methods from RDoc, nor to pass locals to it. You
+therefore will usually use it in combination with another rendering engine:
+
+```ruby
+erb :overview, :locals => { :text => rdoc(:introduction) }
+```
+
+Note that you may also call the `rdoc` method from within other templates:
+
+```ruby
+%h1 Hello From Haml!
+%p= rdoc(:greetings)
+```
+
+Since you cannot call Ruby from RDoc, you cannot use layouts written in
+RDoc. However, it is possible to use another rendering engine for the
+template than for the layout by passing the `:layout_engine` option.
+
+#### AsciiDoc Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://asciidoctor.org/" title="Asciidoctor">Asciidoctor</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.asciidoc</tt>, <tt>.adoc</tt> and <tt>.ad</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>asciidoc :README, :layout_engine => :erb</tt></td>
+  </tr>
+</table>
+
+Since you cannot call Ruby methods directly from an AsciiDoc template, you
+almost always want to pass locals to it.
+
+#### Radius Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://github.com/jlong/radius" title="Radius">Radius</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.radius</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>radius :index, :locals => { :key => 'value' }</tt></td>
+  </tr>
+</table>
+
+Since you cannot call Ruby methods directly from a Radius template, you
+almost always want to pass locals to it.
+
+#### Markaby Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://markaby.github.io/" title="Markaby">Markaby</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.mab</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>markaby { h1 "Welcome!" }</tt></td>
+  </tr>
+</table>
+
+It also takes a block for inline templates (see [example](#inline-templates)).
+
+#### RABL Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://github.com/nesquena/rabl" title="Rabl">Rabl</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.rabl</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>rabl :index</tt></td>
+  </tr>
+</table>
+
+#### Slim Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="http://slim-lang.com/" title="Slim Lang">Slim Lang</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.slim</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>slim :index</tt></td>
+  </tr>
+</table>
+
+#### Creole Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://github.com/minad/creole" title="Creole">Creole</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.creole</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>creole :wiki, :layout_engine => :erb</tt></td>
+  </tr>
+</table>
+
+It is not possible to call methods from Creole, nor to pass locals to it. You
+therefore will usually use it in combination with another rendering engine:
+
+```ruby
+erb :overview, :locals => { :text => creole(:introduction) }
+```
+
+Note that you may also call the `creole` method from within other templates:
+
+```ruby
+%h1 Hello From Haml!
+%p= creole(:greetings)
+```
+
+Since you cannot call Ruby from Creole, you cannot use layouts written in
+Creole. However, it is possible to use another rendering engine for the
+template than for the layout by passing the `:layout_engine` option.
+
+#### MediaWiki Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://github.com/nricciar/wikicloth" title="WikiCloth">WikiCloth</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.mediawiki</tt> and <tt>.mw</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>mediawiki :wiki, :layout_engine => :erb</tt></td>
+  </tr>
+</table>
+
+It is not possible to call methods from MediaWiki markup, nor to pass
+locals to it. You therefore will usually use it in combination with
+another rendering engine:
+
+```ruby
+erb :overview, :locals => { :text => mediawiki(:introduction) }
+```
+
+Note that you may also call the `mediawiki` method from within other
+templates:
+
+```ruby
+%h1 Hello From Haml!
+%p= mediawiki(:greetings)
+```
+
+Since you cannot call Ruby from MediaWiki, you cannot use layouts written in
+MediaWiki. However, it is possible to use another rendering engine for the
+template than for the layout by passing the `:layout_engine` option.
+
+#### CoffeeScript Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td>
+      <a href="https://github.com/josh/ruby-coffee-script" title="Ruby CoffeeScript">
+        CoffeeScript
+      </a> and a
+      <a href="https://github.com/sstephenson/execjs" title="ExecJS">
+        way to execute javascript
+      </a>
+    </td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.coffee</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>coffee :index</tt></td>
+  </tr>
+</table>
+
+#### Stylus Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td>
+      <a href="https://github.com/forgecrafted/ruby-stylus" title="Ruby Stylus">
+        Stylus
+      </a> and a
+      <a href="https://github.com/sstephenson/execjs" title="ExecJS">
+        way to execute javascript
+      </a>
+    </td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.styl</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>stylus :index</tt></td>
+  </tr>
+</table>
+
+Before being able to use Stylus templates, you need to load `stylus` and
+`stylus/tilt` first:
+
+```ruby
+require 'sinatra'
+require 'stylus'
+require 'stylus/tilt'
+
+get '/' do
+  stylus :example
+end
+```
+
+#### Yajl Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://github.com/brianmario/yajl-ruby" title="yajl-ruby">yajl-ruby</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.yajl</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td>
+      <tt>
+        yajl :index,
+             :locals => { :key => 'qux' },
+             :callback => 'present',
+             :variable => 'resource'
+      </tt>
+    </td>
+  </tr>
+</table>
+
+
+The template source is evaluated as a Ruby string, and the
+resulting json variable is converted using `#to_json`:
+
+```ruby
+json = { :foo => 'bar' }
+json[:baz] = key
+```
+
+The `:callback` and `:variable` options can be used to decorate the rendered
+object:
+
+```javascript
+var resource = {"foo":"bar","baz":"qux"};
+present(resource);
+```
+
+#### WLang Templates
+
+<table>
+  <tr>
+    <td>Dependency</td>
+    <td><a href="https://github.com/blambeau/wlang" title="WLang">WLang</a></td>
+  </tr>
+  <tr>
+    <td>File Extension</td>
+    <td><tt>.wlang</tt></td>
+  </tr>
+  <tr>
+    <td>Example</td>
+    <td><tt>wlang :index, :locals => { :key => 'value' }</tt></td>
+  </tr>
+</table>
+
+Since calling ruby methods is not idiomatic in WLang, you almost always
+want to pass locals to it. Layouts written in WLang and `yield` are
+supported, though.
+
+### Accessing Variables in Templates
+
+Templates are evaluated within the same context as route handlers. Instance
+variables set in route handlers are directly accessible by templates:
+
+```ruby
+get '/:id' do
+  @foo = Foo.find(params['id'])
+  haml '%h1= @foo.name'
+end
+```
+
+Or, specify an explicit Hash of local variables:
+
+```ruby
+get '/:id' do
+  foo = Foo.find(params['id'])
+  haml '%h1= bar.name', :locals => { :bar => foo }
+end
+```
+
+This is typically used when rendering templates as partials from within
+other templates.
+
+### Templates with `yield` and nested layouts
+
+A layout is usually just a template that calls `yield`.
+Such a template can be used either through the `:template` option as
+described above, or it can be rendered with a block as follows:
+
+```ruby
+erb :post, :layout => false do
+  erb :index
+end
+```
+
+This code is mostly equivalent to `erb :index, :layout => :post`.
+
+Passing blocks to rendering methods is most useful for creating nested
+layouts:
+
+```ruby
+erb :main_layout, :layout => false do
+  erb :admin_layout do
+    erb :user
+  end
+end
+```
+
+This can also be done in fewer lines of code with:
+
+```ruby
+erb :admin_layout, :layout => :main_layout do
+  erb :user
+end
+```
+
+Currently, the following rendering methods accept a block: `erb`, `haml`,
+`liquid`, `slim `, `wlang`. Also, the general `render` method accepts a block.
+
+### Inline Templates
+
+Templates may be defined at the end of the source file:
+
+```ruby
+require 'sinatra'
+
+get '/' do
+  haml :index
+end
+
+__END__
+
+@@ layout
+%html
+  = yield
+
+@@ index
+%div.title Hello world.
+```
+
+NOTE: Inline templates defined in the source file that requires Sinatra are
+automatically loaded. Call `enable :inline_templates` explicitly if you
+have inline templates in other source files.
+
+### Named Templates
+
+Templates may also be defined using the top-level `template` method:
+
+```ruby
+template :layout do
+  "%html\n  =yield\n"
+end
+
+template :index do
+  '%div.title Hello World!'
+end
+
+get '/' do
+  haml :index
+end
+```
+
+If a template named "layout" exists, it will be used each time a template
+is rendered. You can individually disable layouts by passing
+`:layout => false` or disable them by default via
+`set :haml, :layout => false`:
+
+```ruby
+get '/' do
+  haml :index, :layout => !request.xhr?
+end
+```
+
+### Associating File Extensions
+
+To associate a file extension with a template engine, use
+`Tilt.register`. For instance, if you like to use the file extension
+`tt` for Textile templates, you can do the following:
+
+```ruby
+Tilt.register :tt, Tilt[:textile]
+```
+
+### Adding Your Own Template Engine
+
+First, register your engine with Tilt, then create a rendering method:
+
+```ruby
+Tilt.register :myat, MyAwesomeTemplateEngine
+
+helpers do
+  def myat(*args) render(:myat, *args) end
+end
+
+get '/' do
+  myat :index
+end
+```
+
+Renders `./views/index.myat`. Learn more about
+[Tilt](https://github.com/rtomayko/tilt#readme).
+
+### Using Custom Logic for Template Lookup
+
+To implement your own template lookup mechanism you can write your
+own `#find_template` method:
+
+```ruby
+configure do
+  set :views, [ './views/a', './views/b' ]
+end
+
+def find_template(views, name, engine, &block)
+  Array(views).each do |v|
+    super(v, name, engine, &block)
+  end
+end
+```
+
+## Filters
+
+Before filters are evaluated before each request within the same context
+as the routes will be and can modify the request and response. Instance
+variables set in filters are accessible by routes and templates:
+
+```ruby
+before do
+  @note = 'Hi!'
+  request.path_info = '/foo/bar/baz'
+end
+
+get '/foo/*' do
+  @note #=> 'Hi!'
+  params['splat'] #=> 'bar/baz'
+end
+```
+
+After filters are evaluated after each request within the same context
+as the routes will be and can also modify the request and response.
+Instance variables set in before filters and routes are accessible by
+after filters:
+
+```ruby
+after do
+  puts response.status
+end
+```
+
+Note: Unless you use the `body` method rather than just returning a
+String from the routes, the body will not yet be available in the after
+filter, since it is generated later on.
+
+Filters optionally take a pattern, causing them to be evaluated only if the
+request path matches that pattern:
+
+```ruby
+before '/protected/*' do
+  authenticate!
+end
+
+after '/create/:slug' do |slug|
+  session[:last_slug] = slug
+end
+```
+
+Like routes, filters also take conditions:
+
+```ruby
+before :agent => /Songbird/ do
+  # ...
+end
+
+after '/blog/*', :host_name => 'example.com' do
+  # ...
+end
+```
+
+## Helpers
+
+Use the top-level `helpers` method to define helper methods for use in
+route handlers and templates:
+
+```ruby
+helpers do
+  def bar(name)
+    "#{name}bar"
+  end
+end
+
+get '/:name' do
+  bar(params['name'])
+end
+```
+
+Alternatively, helper methods can be separately defined in a module:
+
+```ruby
+module FooUtils
+  def foo(name) "#{name}foo" end
+end
+
+module BarUtils
+  def bar(name) "#{name}bar" end
+end
+
+helpers FooUtils, BarUtils
+```
+
+The effect is the same as including the modules in the application class.
+
+### Using Sessions
+
+A session is used to keep state during requests. If activated, you have one
+session hash per user session:
+
+```ruby
+enable :sessions
+
+get '/' do
+  "value = " << session[:value].inspect
+end
+
+get '/:value' do
+  session['value'] = params['value']
+end
+```
+
+#### Session Secret Security
+
+To improve security, the session data in the cookie is signed with a session
+secret using `HMAC-SHA1`. This session secret should optimally be a
+cryptographically secure random value of an appropriate length which for
+`HMAC-SHA1` is greater than or equal to 64 bytes (512 bits, 128 hex
+characters). You would be advised not to use a secret that is less than 32
+bytes of randomness (256 bits, 64 hex characters). It is therefore **very
+important** that you don't just make the secret up, but instead use a secure
+random number generator to create it. Humans are extremely bad at generating
+random values.
+
+By default, a 32 byte secure random session secret is generated for you by
+Sinatra, but it will change with every restart of your application. If you
+have multiple instances of your application, and you let Sinatra generate the
+key, each instance would then have a different session key which is probably
+not what you want.
+
+For better security and usability it's
+[recommended](https://12factor.net/config) that you generate a secure random
+secret and store it in an environment variable on each host running your
+application so that all of your application instances will share the same
+secret. You should periodically rotate this session secret to a new value.
+Here are some examples of how you might create a 64-byte secret and set it:
+
+**Session Secret Generation**
+
+```text
+$ ruby -e "require 'securerandom'; puts SecureRandom.hex(64)"
+99ae8af...snip...ec0f262ac
+```
+
+**Session Secret Generation (Bonus Points)**
+
+Use the [sysrandom gem](https://github.com/cryptosphere/sysrandom#readme) to
+use the system RNG facilities to generate random values instead of
+userspace `OpenSSL` which MRI Ruby currently defaults to:
+
+```text
+$ gem install sysrandom
+Building native extensions.  This could take a while...
+Successfully installed sysrandom-1.x
+1 gem installed
+
+$ ruby -e "require 'sysrandom/securerandom'; puts SecureRandom.hex(64)"
+99ae8af...snip...ec0f262ac
+```
+
+**Session Secret Environment Variable**
+
+Set a `SESSION_SECRET` environment variable for Sinatra to the value you
+generated. Make this value persistent across reboots of your host. Since the
+method for doing this will vary across systems this is for illustrative
+purposes only:
+
+```bash
+# echo "export SESSION_SECRET=99ae8af...snip...ec0f262ac" >> ~/.bashrc
+```
+
+**Session Secret App Config**
+
+Set up your app config to fail-safe to a secure random secret
+if the `SESSION_SECRET` environment variable is not available.
+
+For bonus points use the [sysrandom
+gem](https://github.com/cryptosphere/sysrandom#readme) here as well:
+
+```ruby
+require 'securerandom'
+# -or- require 'sysrandom/securerandom'
+set :session_secret, ENV.fetch('SESSION_SECRET') { SecureRandom.hex(64) }
+```
+
+#### Session Config
+
+If you want to configure it further, you may also store a hash with options
+in the `sessions` setting:
+
+```ruby
+set :sessions, :domain => 'foo.com'
+```
+
+To share your session across other apps on subdomains of foo.com, prefix the
+domain with a *.* like this instead:
+
+```ruby
+set :sessions, :domain => '.foo.com'
+```
+
+#### Choosing Your Own Session Middleware
+
+Note that `enable :sessions` actually stores all data in a cookie. This
+might not always be what you want (storing lots of data will increase your
+traffic, for instance). You can use any Rack session middleware in order to
+do so, one of the following methods can be used:
+
+```ruby
+enable :sessions
+set :session_store, Rack::Session::Pool
+```
+
+Or to set up sessions with a hash of options:
+
+```ruby
+set :sessions, :expire_after => 2592000
+set :session_store, Rack::Session::Pool
+```
+
+Another option is to **not** call `enable :sessions`, but instead pull in
+your middleware of choice as you would any other middleware.
+
+It is important to note that when using this method, session based
+protection **will not be enabled by default**.
+
+The Rack middleware to do that will also need to be added:
+
+```ruby
+use Rack::Session::Pool, :expire_after => 2592000
+use Rack::Protection::RemoteToken
+use Rack::Protection::SessionHijacking
+```
+
+See '[Configuring attack protection](#configuring-attack-protection)' for more information.
+
+### Halting
+
+To immediately stop a request within a filter or route use:
+
+```ruby
+halt
+```
+
+You can also specify the status when halting:
+
+```ruby
+halt 410
+```
+
+Or the body:
+
+```ruby
+halt 'this will be the body'
+```
+
+Or both:
+
+```ruby
+halt 401, 'go away!'
+```
+
+With headers:
+
+```ruby
+halt 402, {'Content-Type' => 'text/plain'}, 'revenge'
+```
+
+It is of course possible to combine a template with `halt`:
+
+```ruby
+halt erb(:error)
+```
+
+### Passing
+
+A route can punt processing to the next matching route using `pass`:
+
+```ruby
+get '/guess/:who' do
+  pass unless params['who'] == 'Frank'
+  'You got me!'
+end
+
+get '/guess/*' do
+  'You missed!'
+end
+```
+
+The route block is immediately exited and control continues with the next
+matching route. If no matching route is found, a 404 is returned.
+
+### Triggering Another Route
+
+Sometimes `pass` is not what you want, instead, you would like to get the
+result of calling another route. Simply use `call` to achieve this:
+
+```ruby
+get '/foo' do
+  status, headers, body = call env.merge("PATH_INFO" => '/bar')
+  [status, headers, body.map(&:upcase)]
+end
+
+get '/bar' do
+  "bar"
+end
+```
+
+Note that in the example above, you would ease testing and increase
+performance by simply moving `"bar"` into a helper used by both `/foo` and
+`/bar`.
+
+If you want the request to be sent to the same application instance rather
+than a duplicate, use `call!` instead of `call`.
+
+Check out the Rack specification if you want to learn more about `call`.
+
+### Setting Body, Status Code, and Headers
+
+It is possible and recommended to set the status code and response body with
+the return value of the route block. However, in some scenarios, you might
+want to set the body at an arbitrary point in the execution flow. You can do
+so with the `body` helper method. If you do so, you can use that method from
+thereon to access the body:
+
+```ruby
+get '/foo' do
+  body "bar"
+end
+
+after do
+  puts body
+end
+```
+
+It is also possible to pass a block to `body`, which will be executed by the
+Rack handler (this can be used to implement streaming, [see "Return Values"](#return-values)).
+
+Similar to the body, you can also set the status code and headers:
+
+```ruby
+get '/foo' do
+  status 418
+  headers \
+    "Allow"   => "BREW, POST, GET, PROPFIND, WHEN",
+    "Refresh" => "Refresh: 20; https://ietf.org/rfc/rfc2324.txt"
+  body "I'm a teapot!"
+end
+```
+
+Like `body`, `headers` and `status` with no arguments can be used to access
+their current values.
+
+### Streaming Responses
+
+Sometimes you want to start sending out data while still generating parts of
+the response body. In extreme examples, you want to keep sending data until
+the client closes the connection. You can use the `stream` helper to avoid
+creating your own wrapper:
+
+```ruby
+get '/' do
+  stream do |out|
+    out << "It's gonna be legen -\n"
+    sleep 0.5
+    out << " (wait for it) \n"
+    sleep 1
+    out << "- dary!\n"
+  end
+end
+```
+
+This allows you to implement streaming APIs,
+[Server Sent Events](https://w3c.github.io/eventsource/), and can be used as
+the basis for [WebSockets](https://en.wikipedia.org/wiki/WebSocket). It can
+also be used to increase throughput if some but not all content depends on a
+slow resource.
+
+Note that the streaming behavior, especially the number of concurrent
+requests, highly depends on the webserver used to serve the application.
+Some servers might not even support streaming at all. If the server does not
+support streaming, the body will be sent all at once after the block passed
+to `stream` finishes executing. Streaming does not work at all with Shotgun.
+
+If the optional parameter is set to `keep_open`, it will not call `close` on
+the stream object, allowing you to close it at any later point in the
+execution flow. This only works on evented servers, like Rainbows.
+Other servers will still close the stream:
+
+```ruby
+# config.ru
+require 'sinatra/base'
+
+class App < Sinatra::Base
+  connections = []
+
+  get '/subscribe', provides: 'text/event-stream'  do
+    # register a client's interest in server events
+    stream(:keep_open) do |out|
+      connections << out
+      # purge dead connections
+      connections.reject!(&:closed?)
+    end
+  end
+
+  post '/' do
+    connections.each do |out|
+      # notify client that a new message has arrived
+      out << "data: #{params[:msg]}\n\n"
+
+      # indicate client to connect again
+      out.close
+    end
+
+    204 # response without entity body
+  end
+end
+
+run App
+```
+
+```ruby
+# rainbows.conf
+Rainbows! do
+  use :EventMachine
+end
+````
+
+Run:
+
+```shell
+rainbows -c rainbows.conf
+```
+
+It's also possible for the client to close the connection when trying to
+write to the socket. Because of this, it's recommended to check
+`out.closed?` before trying to write.
+
+### Logging
+
+In the request scope, the `logger` helper exposes a `Logger` instance:
+
+```ruby
+get '/' do
+  logger.info "loading data"
+  # ...
+end
+```
+
+This logger will automatically take your Rack handler's logging settings into
+account. If logging is disabled, this method will return a dummy object, so
+you do not have to worry about it in your routes and filters.
+
+Note that logging is only enabled for `Sinatra::Application` by default, so
+if you inherit from `Sinatra::Base`, you probably want to enable it yourself:
+
+```ruby
+class MyApp < Sinatra::Base
+  configure :production, :development do
+    enable :logging
+  end
+end
+```
+
+To avoid any logging middleware to be set up, set the `logging` option to
+`nil`. However, keep in mind that `logger` will in that case return `nil`. A
+common use case is when you want to set your own logger. Sinatra will use
+whatever it will find in `env['rack.logger']`.
+
+### Mime Types
+
+When using `send_file` or static files you may have mime types Sinatra
+doesn't understand. Use `mime_type` to register them by file extension:
+
+```ruby
+configure do
+  mime_type :foo, 'text/foo'
+end
+```
+
+You can also use it with the `content_type` helper:
+
+```ruby
+get '/' do
+  content_type :foo
+  "foo foo foo"
+end
+```
+
+### Generating URLs
+
+For generating URLs you should use the `url` helper method, for instance, in
+Haml:
+
+```ruby
+%a{:href => url('/foo')} foo
+```
+
+It takes reverse proxies and Rack routers into account - if present.
+
+This method is also aliased to `to` (see [below](#browser-redirect) for an example).
+
+### Browser Redirect
+
+You can trigger a browser redirect with the `redirect` helper method:
+
+```ruby
+get '/foo' do
+  redirect to('/bar')
+end
+```
+
+Any additional parameters are handled like arguments passed to `halt`:
+
+```ruby
+redirect to('/bar'), 303
+redirect 'http://www.google.com/', 'wrong place, buddy'
+```
+
+You can also easily redirect back to the page the user came from with
+`redirect back`:
+
+```ruby
+get '/foo' do
+  "<a href='/bar'>do something</a>"
+end
+
+get '/bar' do
+  do_something
+  redirect back
+end
+```
+
+To pass arguments with a redirect, either add them to the query:
+
+```ruby
+redirect to('/bar?sum=42')
+```
+
+Or use a session:
+
+```ruby
+enable :sessions
+
+get '/foo' do
+  session[:secret] = 'foo'
+  redirect to('/bar')
+end
+
+get '/bar' do
+  session[:secret]
+end
+```
+
+### Cache Control
+
+Setting your headers correctly is the foundation for proper HTTP caching.
+
+You can easily set the Cache-Control header like this:
+
+```ruby
+get '/' do
+  cache_control :public
+  "cache it!"
+end
+```
+
+Pro tip: Set up caching in a before filter:
+
+```ruby
+before do
+  cache_control :public, :must_revalidate, :max_age => 60
+end
+```
+
+If you are using the `expires` helper to set the corresponding header,
+`Cache-Control` will be set automatically for you:
+
+```ruby
+before do
+  expires 500, :public, :must_revalidate
+end
+```
+
+To properly use caches, you should consider using `etag` or `last_modified`.
+It is recommended to call those helpers *before* doing any heavy lifting, as
+they will immediately flush a response if the client already has the current
+version in its cache:
+
+```ruby
+get "/article/:id" do
+  @article = Article.find params['id']
+  last_modified @article.updated_at
+  etag @article.sha1
+  erb :article
+end
+```
+
+It is also possible to use a
+[weak ETag](https://en.wikipedia.org/wiki/HTTP_ETag#Strong_and_weak_validation):
+
+```ruby
+etag @article.sha1, :weak
+```
+
+These helpers will not do any caching for you, but rather feed the necessary
+information to your cache. If you are looking for a quick
+reverse-proxy caching solution, try
+[rack-cache](https://github.com/rtomayko/rack-cache#readme):
+
+```ruby
+require "rack/cache"
+require "sinatra"
+
+use Rack::Cache
+
+get '/' do
+  cache_control :public, :max_age => 36000
+  sleep 5
+  "hello"
+end
+```
+
+Use the `:static_cache_control` setting (see [below](#cache-control)) to add
+`Cache-Control` header info to static files.
+
+According to RFC 2616, your application should behave differently if the
+If-Match or If-None-Match header is set to `*`, depending on whether the
+resource requested is already in existence. Sinatra assumes resources for
+safe (like get) and idempotent (like put) requests are already in existence,
+whereas other resources (for instance post requests) are treated as new
+resources. You can change this behavior by passing in a `:new_resource`
+option:
+
+```ruby
+get '/create' do
+  etag '', :new_resource => true
+  Article.create
+  erb :new_article
+end
+```
+
+If you still want to use a weak ETag, pass in a `:kind` option:
+
+```ruby
+etag '', :new_resource => true, :kind => :weak
+```
+
+### Sending Files
+
+To return the contents of a file as the response, you can use the `send_file`
+helper method:
+
+```ruby
+get '/' do
+  send_file 'foo.png'
+end
+```
+
+It also takes options:
+
+```ruby
+send_file 'foo.png', :type => :jpg
+```
+
+The options are:
+
+<dl>
+  <dt>filename</dt>
+    <dd>File name to be used in the response,
+    defaults to the real file name.</dd>
+  <dt>last_modified</dt>
+    <dd>Value for Last-Modified header, defaults to the file's mtime.</dd>
+
+  <dt>type</dt>
+    <dd>Value for Content-Type header, guessed from the file extension if
+    missing.</dd>
+
+  <dt>disposition</dt>
+    <dd>
+      Value for Content-Disposition header, possible values: <tt>nil</tt>
+      (default), <tt>:attachment</tt> and <tt>:inline</tt>
+    </dd>
+
+  <dt>length</dt>
+    <dd>Value for Content-Length header, defaults to file size.</dd>
+
+  <dt>status</dt>
+    <dd>
+      Status code to be sent. Useful when sending a static file as an error
+      page. If supported by the Rack handler, other means than streaming
+      from the Ruby process will be used. If you use this helper method,
+      Sinatra will automatically handle range requests.
+    </dd>
+</dl>
+
+### Accessing the Request Object
+
+The incoming request object can be accessed from request level (filter,
+routes, error handlers) through the `request` method:
+
+```ruby
+# app running on http://example.com/example
+get '/foo' do
+  t = %w[text/css text/html application/javascript]
+  request.accept              # ['text/html', '*/*']
+  request.accept? 'text/xml'  # true
+  request.preferred_type(t)   # 'text/html'
+  request.body                # request body sent by the client (see below)
+  request.scheme              # "http"
+  request.script_name         # "/example"
+  request.path_info           # "/foo"
+  request.port                # 80
+  request.request_method      # "GET"
+  request.query_string        # ""
+  request.content_length      # length of request.body
+  request.media_type          # media type of request.body
+  request.host                # "example.com"
+  request.get?                # true (similar methods for other verbs)
+  request.form_data?          # false
+  request["some_param"]       # value of some_param parameter. [] is a shortcut to the params hash.
+  request.referrer            # the referrer of the client or '/'
+  request.user_agent          # user agent (used by :agent condition)
+  request.cookies             # hash of browser cookies
+  request.xhr?                # is this an ajax request?
+  request.url                 # "http://example.com/example/foo"
+  request.path                # "/example/foo"
+  request.ip                  # client IP address
+  request.secure?             # false (would be true over ssl)
+  request.forwarded?          # true (if running behind a reverse proxy)
+  request.env                 # raw env hash handed in by Rack
+end
+```
+
+Some options, like `script_name` or `path_info`, can also be written:
+
+```ruby
+before { request.path_info = "/" }
+
+get "/" do
+  "all requests end up here"
+end
+```
+
+The `request.body` is an IO or StringIO object:
+
+```ruby
+post "/api" do
+  request.body.rewind  # in case someone already read it
+  data = JSON.parse request.body.read
+  "Hello #{data['name']}!"
+end
+```
+
+### Attachments
+
+You can use the `attachment` helper to tell the browser the response should
+be stored on disk rather than displayed in the browser:
+
+```ruby
+get '/' do
+  attachment
+  "store it!"
+end
+```
+
+You can also pass it a file name:
+
+```ruby
+get '/' do
+  attachment "info.txt"
+  "store it!"
+end
+```
+
+### Dealing with Date and Time
+
+Sinatra offers a `time_for` helper method that generates a Time object from
+the given value. It is also able to convert `DateTime`, `Date` and similar
+classes:
+
+```ruby
+get '/' do
+  pass if Time.now > time_for('Dec 23, 2016')
+  "still time"
+end
+```
+
+This method is used internally by `expires`, `last_modified` and akin. You
+can therefore easily extend the behavior of those methods by overriding
+`time_for` in your application:
+
+```ruby
+helpers do
+  def time_for(value)
+    case value
+    when :yesterday then Time.now - 24*60*60
+    when :tomorrow  then Time.now + 24*60*60
+    else super
+    end
+  end
+end
+
+get '/' do
+  last_modified :yesterday
+  expires :tomorrow
+  "hello"
+end
+```
+
+### Looking Up Template Files
+
+The `find_template` helper is used to find template files for rendering:
+
+```ruby
+find_template settings.views, 'foo', Tilt[:haml] do |file|
+  puts "could be #{file}"
+end
+```
+
+This is not really useful. But it is useful that you can actually override
+this method to hook in your own lookup mechanism. For instance, if you want
+to be able to use more than one view directory:
+
+```ruby
+set :views, ['views', 'templates']
+
+helpers do
+  def find_template(views, name, engine, &block)
+    Array(views).each { |v| super(v, name, engine, &block) }
+  end
+end
+```
+
+Another example would be using different directories for different engines:
+
+```ruby
+set :views, :sass => 'views/sass', :haml => 'templates', :default => 'views'
+
+helpers do
+  def find_template(views, name, engine, &block)
+    _, folder = views.detect { |k,v| engine == Tilt[k] }
+    folder ||= views[:default]
+    super(folder, name, engine, &block)
+  end
+end
+```
+
+You can also easily wrap this up in an extension and share it with others!
+
+Note that `find_template` does not check if the file really exists but
+rather calls the given block for all possible paths. This is not a
+performance issue, since `render` will use `break` as soon as a file is
+found. Also, template locations (and content) will be cached if you are not
+running in development mode. You should keep that in mind if you write a
+really crazy method.
+
+## Configuration
+
+Run once, at startup, in any environment:
+
+```ruby
+configure do
+  # setting one option
+  set :option, 'value'
+
+  # setting multiple options
+  set :a => 1, :b => 2
+
+  # same as `set :option, true`
+  enable :option
+
+  # same as `set :option, false`
+  disable :option
+
+  # you can also have dynamic settings with blocks
+  set(:css_dir) { File.join(views, 'css') }
+end
+```
+
+Run only when the environment (`APP_ENV` environment variable) is set to
+`:production`:
+
+```ruby
+configure :production do
+  ...
+end
+```
+
+Run when the environment is set to either `:production` or `:test`:
+
+```ruby
+configure :production, :test do
+  ...
+end
+```
+
+You can access those options via `settings`:
+
+```ruby
+configure do
+  set :foo, 'bar'
+end
+
+get '/' do
+  settings.foo? # => true
+  settings.foo  # => 'bar'
+  ...
+end
+```
+
+### Configuring attack protection
+
+Sinatra is using
+[Rack::Protection](https://github.com/sinatra/sinatra/tree/master/rack-protection#readme) to
+defend your application against common, opportunistic attacks. You can
+easily disable this behavior (which will open up your application to tons
+of common vulnerabilities):
+
+```ruby
+disable :protection
+```
+
+To skip a single defense layer, set `protection` to an options hash:
+
+```ruby
+set :protection, :except => :path_traversal
+```
+You can also hand in an array in order to disable a list of protections:
+
+```ruby
+set :protection, :except => [:path_traversal, :session_hijacking]
+```
+
+By default, Sinatra will only set up session based protection if `:sessions`
+have been enabled. See '[Using Sessions](#using-sessions)'. Sometimes you may want to set up
+sessions "outside" of the Sinatra app, such as in the config.ru or with a
+separate `Rack::Builder` instance. In that case, you can still set up session
+based protection by passing the `:session` option:
+
+```ruby
+set :protection, :session => true
+```
+
+### Available Settings
+
+<dl>
+  <dt>absolute_redirects</dt>
+    <dd>
+      If disabled, Sinatra will allow relative redirects, however, Sinatra
+      will no longer conform with RFC 2616 (HTTP 1.1), which only allows
+      absolute redirects.
+    </dd>
+    <dd>
+      Enable if your app is running behind a reverse proxy that has not been
+      set up properly. Note that the <tt>url</tt> helper will still produce
+      absolute URLs, unless you pass in <tt>false</tt> as the second
+      parameter.
+    </dd>
+    <dd>Disabled by default.</dd>
+
+  <dt>add_charset</dt>
+    <dd>
+      Mime types the <tt>content_type</tt> helper will automatically add the
+      charset info to. You should add to it rather than overriding this
+      option: <tt>settings.add_charset << "application/foobar"</tt>
+    </dd>
+
+  <dt>app_file</dt>
+    <dd>
+      Path to the main application file, used to detect project root, views
+      and public folder and inline templates.
+    </dd>
+
+  <dt>bind</dt>
+    <dd>
+      IP address to bind to (default: <tt>0.0.0.0</tt> <em>or</em>
+      <tt>localhost</tt> if your `environment` is set to development). Only
+      used for built-in server.
+    </dd>
+
+  <dt>default_content_type</dt>
+  <dd>
+    Content-Type to assume if unknown (defaults to <tt>"text/html"</tt>). Set
+    to <tt>nil</tt> to not set a default Content-Type on every response; when
+    configured so, you must set the Content-Type manually when emitting content
+    or the user-agent will have to sniff it (or, if <tt>nosniff</tt> is enabled
+    in Rack::Protection::XSSHeader, assume <tt>application/octet-stream</tt>).
+  </dd>
+
+  <dt>default_encoding</dt>
+    <dd>Encoding to assume if unknown (defaults to <tt>"utf-8"</tt>).</dd>
+
+  <dt>dump_errors</dt>
+    <dd>Display errors in the log. Enabled by default unless environment is "test".</dd>
+
+  <dt>environment</dt>
+    <dd>
+      Current environment. Defaults to <tt>ENV['APP_ENV']</tt>, or
+      <tt>"development"</tt> if not available.
+    </dd>
+
+  <dt>logging</dt>
+    <dd>Use the logger.</dd>
+
+  <dt>lock</dt>
+    <dd>
+      Places a lock around every request, only running processing on request
+      per Ruby process concurrently.
+    </dd>
+    <dd>Enabled if your app is not thread-safe. Disabled by default.</dd>
+
+  <dt>method_override</dt>
+    <dd>
+      Use <tt>_method</tt> magic to allow put/delete forms in browsers that
+      don't support it.
+    </dd>
+
+  <dt>mustermann_opts</dt>
+  <dd>
+    A default hash of options to pass to Mustermann.new when compiling routing
+    paths.
+  </dd>
+
+  <dt>port</dt>
+    <dd>Port to listen on. Only used for built-in server.</dd>
+
+  <dt>prefixed_redirects</dt>
+    <dd>
+      Whether or not to insert <tt>request.script_name</tt> into redirects
+      if no absolute path is given. That way <tt>redirect '/foo'</tt> would
+        behave like <tt>redirect to('/foo')</tt>. Disabled by default.
+    </dd>
+
+  <dt>protection</dt>
+    <dd>
+      Whether or not to enable web attack protections. See protection section
+      above.
+    </dd>
+
+  <dt>public_dir</dt>
+    <dd>Alias for <tt>public_folder</tt>. See below.</dd>
+
+  <dt>public_folder</dt>
+    <dd>
+      Path to the folder public files are served from. Only used if static
+      file serving is enabled (see <tt>static</tt> setting below). Inferred
+      from <tt>app_file</tt> setting if not set.
+    </dd>
+
+  <dt>quiet</dt>
+    <dd>
+      Disables logs generated by Sinatra's start and stop commands.
+      <tt>false</tt> by default.
+    </dd>
+
+  <dt>reload_templates</dt>
+    <dd>
+      Whether or not to reload templates between requests. Enabled in
+      development mode.
+    </dd>
+
+  <dt>root</dt>
+    <dd>
+      Path to project root folder. Inferred from <tt>app_file</tt> setting
+      if not set.
+    </dd>
+
+  <dt>raise_errors</dt>
+    <dd>
+      Raise exceptions (will stop application). Enabled by default when
+      <tt>environment</tt> is set to <tt>"test"</tt>, disabled otherwise.
+    </dd>
+
+  <dt>run</dt>
+    <dd>
+      If enabled, Sinatra will handle starting the web server. Do not
+      enable if using rackup or other means.
+    </dd>
+
+  <dt>running</dt>
+    <dd>Is the built-in server running now? Do not change this setting!</dd>
+
+  <dt>server</dt>
+    <dd>
+      Server or list of servers to use for built-in server. Order indicates
+      priority, default depends on Ruby implementation.
+    </dd>
+
+  <dt>server_settings</dt>
+    <dd>
+      If you are using a WEBrick web server, presumably for your development
+      environment, you can pass a hash of options to <tt>server_settings</tt>,
+      such as <tt>SSLEnable</tt> or <tt>SSLVerifyClient</tt>. However, web
+      servers such as Puma do not support this, so you can set
+      <tt>server_settings</tt> by defining it as a method when you call
+      <tt>configure</tt>.
+    </dd>
+
+  <dt>sessions</dt>
+    <dd>
+      Enable cookie-based sessions support using
+      <tt>Rack::Session::Cookie</tt>. See 'Using Sessions' section for more
+      information.
+    </dd>
+
+  <dt>session_store</dt>
+    <dd>
+      The Rack session middleware used. Defaults to
+      <tt>Rack::Session::Cookie</tt>. See 'Using Sessions' section for more
+      information.
+    </dd>
+
+  <dt>show_exceptions</dt>
+    <dd>
+      Show a stack trace in the browser when an exception happens. Enabled by
+      default when <tt>environment</tt> is set to <tt>"development"</tt>,
+      disabled otherwise.
+    </dd>
+    <dd>
+      Can also be set to <tt>:after_handler</tt> to trigger app-specified
+      error handling before showing a stack trace in the browser.
+    </dd>
+
+  <dt>static</dt>
+    <dd>Whether Sinatra should handle serving static files.</dd>
+    <dd>Disable when using a server able to do this on its own.</dd>
+    <dd>Disabling will boost performance.</dd>
+    <dd>
+      Enabled by default in classic style, disabled for modular apps.
+    </dd>
+
+  <dt>static_cache_control</dt>
+    <dd>
+      When Sinatra is serving static files, set this to add
+      <tt>Cache-Control</tt> headers to the responses. Uses the
+      <tt>cache_control</tt> helper. Disabled by default.
+    </dd>
+    <dd>
+      Use an explicit array when setting multiple values:
+      <tt>set :static_cache_control, [:public, :max_age => 300]</tt>
+    </dd>
+
+  <dt>threaded</dt>
+    <dd>
+      If set to <tt>true</tt>, will tell server to use
+      <tt>EventMachine.defer</tt> for processing the request.
+    </dd>
+
+  <dt>traps</dt>
+    <dd>Whether Sinatra should handle system signals.</dd>
+
+  <dt>views</dt>
+    <dd>
+      Path to the views folder. Inferred from <tt>app_file</tt> setting if
+      not set.
+    </dd>
+
+  <dt>x_cascade</dt>
+    <dd>
+      Whether or not to set the X-Cascade header if no route matches.
+      Defaults to <tt>true</tt>.
+    </dd>
+</dl>
+
+## Environments
+
+There are three predefined `environments`: `"development"`,
+`"production"` and `"test"`. Environments can be set through the
+`APP_ENV` environment variable. The default value is `"development"`.
+In the `"development"` environment all templates are reloaded between
+requests, and special `not_found` and `error` handlers display stack
+traces in your browser. In the `"production"` and `"test"` environments,
+templates are cached by default.
+
+To run different environments, set the `APP_ENV` environment variable:
+
+```shell
+APP_ENV=production ruby my_app.rb
+```
+
+You can use predefined methods: `development?`, `test?` and `production?` to
+check the current environment setting:
+
+```ruby
+get '/' do
+  if settings.development?
+    "development!"
+  else
+    "not development!"
+  end
+end
+```
+
+## Error Handling
+
+Error handlers run within the same context as routes and before filters,
+which means you get all the goodies it has to offer, like `haml`, `erb`,
+`halt`, etc.
+
+### Not Found
+
+When a `Sinatra::NotFound` exception is raised, or the response's status
+code is 404, the `not_found` handler is invoked:
+
+```ruby
+not_found do
+  'This is nowhere to be found.'
+end
+```
+
+### Error
+
+The `error` handler is invoked any time an exception is raised from a route
+block or a filter. But note in development it will only run if you set the
+show exceptions option to `:after_handler`:
+
+```ruby
+set :show_exceptions, :after_handler
+```
+
+The exception object can be obtained from the `sinatra.error` Rack variable:
+
+```ruby
+error do
+  'Sorry there was a nasty error - ' + env['sinatra.error'].message
+end
+```
+
+Custom errors:
+
+```ruby
+error MyCustomError do
+  'So what happened was...' + env['sinatra.error'].message
+end
+```
+
+Then, if this happens:
+
+```ruby
+get '/' do
+  raise MyCustomError, 'something bad'
+end
+```
+
+You get this:
+
+```
+So what happened was... something bad
+```
+
+Alternatively, you can install an error handler for a status code:
+
+```ruby
+error 403 do
+  'Access forbidden'
+end
+
+get '/secret' do
+  403
+end
+```
+
+Or a range:
+
+```ruby
+error 400..510 do
+  'Boom'
+end
+```
+
+Sinatra installs special `not_found` and `error` handlers when
+running under the development environment to display nice stack traces
+and additional debugging information in your browser.
+
+## Rack Middleware
+
+Sinatra rides on [Rack](https://rack.github.io/), a minimal standard
+interface for Ruby web frameworks. One of Rack's most interesting
+capabilities for application developers is support for "middleware" --
+components that sit between the server and your application monitoring
+and/or manipulating the HTTP request/response to provide various types
+of common functionality.
+
+Sinatra makes building Rack middleware pipelines a cinch via a top-level
+`use` method:
+
+```ruby
+require 'sinatra'
+require 'my_custom_middleware'
+
+use Rack::Lint
+use MyCustomMiddleware
+
+get '/hello' do
+  'Hello World'
+end
+```
+
+The semantics of `use` are identical to those defined for the
+[Rack::Builder](http://www.rubydoc.info/github/rack/rack/master/Rack/Builder) DSL
+(most frequently used from rackup files). For example, the `use` method
+accepts multiple/variable args as well as blocks:
+
+```ruby
+use Rack::Auth::Basic do |username, password|
+  username == 'admin' && password == 'secret'
+end
+```
+
+Rack is distributed with a variety of standard middleware for logging,
+debugging, URL routing, authentication, and session handling. Sinatra uses
+many of these components automatically based on configuration so you
+typically don't have to `use` them explicitly.
+
+You can find useful middleware in
+[rack](https://github.com/rack/rack/tree/master/lib/rack),
+[rack-contrib](https://github.com/rack/rack-contrib#readme),
+or in the [Rack wiki](https://github.com/rack/rack/wiki/List-of-Middleware).
+
+## Testing
+
+Sinatra tests can be written using any Rack-based testing library or
+framework.
+[Rack::Test](http://www.rubydoc.info/github/brynary/rack-test/master/frames)
+is recommended:
+
+```ruby
+require 'my_sinatra_app'
+require 'minitest/autorun'
+require 'rack/test'
+
+class MyAppTest < Minitest::Test
+  include Rack::Test::Methods
+
+  def app
+    Sinatra::Application
+  end
+
+  def test_my_default
+    get '/'
+    assert_equal 'Hello World!', last_response.body
+  end
+
+  def test_with_params
+    get '/meet', :name => 'Frank'
+    assert_equal 'Hello Frank!', last_response.body
+  end
+
+  def test_with_user_agent
+    get '/', {}, 'HTTP_USER_AGENT' => 'Songbird'
+    assert_equal "You're using Songbird!", last_response.body
+  end
+end
+```
+
+Note: If you are using Sinatra in the modular style, replace
+`Sinatra::Application` above with the class name of your app.
+
+## Sinatra::Base - Middleware, Libraries, and Modular Apps
+
+Defining your app at the top-level works well for micro-apps but has
+considerable drawbacks when building reusable components such as Rack
+middleware, Rails metal, simple libraries with a server component, or even
+Sinatra extensions. The top-level assumes a micro-app style configuration
+(e.g., a single application file, `./public` and `./views`
+directories, logging, exception detail page, etc.). That's where
+`Sinatra::Base` comes into play:
+
+```ruby
+require 'sinatra/base'
+
+class MyApp < Sinatra::Base
+  set :sessions, true
+  set :foo, 'bar'
+
+  get '/' do
+    'Hello world!'
+  end
+end
+```
+
+The methods available to `Sinatra::Base` subclasses are exactly the same
+as those available via the top-level DSL. Most top-level apps can be
+converted to `Sinatra::Base` components with two modifications:
+
+* Your file should require `sinatra/base` instead of `sinatra`;
+  otherwise, all of Sinatra's DSL methods are imported into the main
+  namespace.
+* Put your app's routes, error handlers, filters, and options in a subclass
+  of `Sinatra::Base`.
+
+`Sinatra::Base` is a blank slate. Most options are disabled by default,
+including the built-in server. See [Configuring
+Settings](http://www.sinatrarb.com/configuration.html) for details on
+available options and their behavior. If you want behavior more similar
+to when you define your app at the top level (also known as Classic
+style), you can subclass `Sinatra::Application`:
+
+```ruby
+require 'sinatra/base'
+
+class MyApp < Sinatra::Application
+  get '/' do
+    'Hello world!'
+  end
+end
+```
+
+### Modular vs. Classic Style
+
+Contrary to common belief, there is nothing wrong with the classic
+style. If it suits your application, you do not have to switch to a
+modular application.
+
+The main disadvantage of using the classic style rather than the modular
+style is that you will only have one Sinatra application per Ruby
+process. If you plan to use more than one, switch to the modular style.
+There is no reason you cannot mix the modular and classic styles.
+
+If switching from one style to the other, you should be aware of
+slightly different default settings:
+
+<table>
+  <tr>
+    <th>Setting</th>
+    <th>Classic</th>
+    <th>Modular</th>
+    <th>Modular</th>
+  </tr>
+
+  <tr>
+    <td>app_file</td>
+    <td>file loading sinatra</td>
+    <td>file subclassing Sinatra::Base</td>
+    <td>file subclassing Sinatra::Application</td>
+  </tr>
+
+  <tr>
+    <td>run</td>
+    <td>$0 == app_file</td>
+    <td>false</td>
+    <td>false</td>
+  </tr>
+
+  <tr>
+    <td>logging</td>
+    <td>true</td>
+    <td>false</td>
+    <td>true</td>
+  </tr>
+
+  <tr>
+    <td>method_override</td>
+    <td>true</td>
+    <td>false</td>
+    <td>true</td>
+  </tr>
+
+  <tr>
+    <td>inline_templates</td>
+    <td>true</td>
+    <td>false</td>
+    <td>true</td>
+  </tr>
+
+  <tr>
+    <td>static</td>
+    <td>true</td>
+    <td>File.exist?(public_folder)</td>
+    <td>true</td>
+  </tr>
+</table>
+
+### Serving a Modular Application
+
+There are two common options for starting a modular app, actively
+starting with `run!`:
+
+```ruby
+# my_app.rb
+require 'sinatra/base'
+
+class MyApp < Sinatra::Base
+  # ... app code here ...
+
+  # start the server if ruby file executed directly
+  run! if app_file == $0
+end
+```
+
+Start with:
+
+```shell
+ruby my_app.rb
+```
+
+Or with a `config.ru` file, which allows using any Rack handler:
+
+```ruby
+# config.ru (run with rackup)
+require './my_app'
+run MyApp
+```
+
+Run:
+
+```shell
+rackup -p 4567
+```
+
+### Using a Classic Style Application with a config.ru
+
+Write your app file:
+
+```ruby
+# app.rb
+require 'sinatra'
+
+get '/' do
+  'Hello world!'
+end
+```
+
+And a corresponding `config.ru`:
+
+```ruby
+require './app'
+run Sinatra::Application
+```
+
+### When to use a config.ru?
+
+A `config.ru` file is recommended if:
+
+* You want to deploy with a different Rack handler (Passenger, Unicorn,
+  Heroku, ...).
+* You want to use more than one subclass of `Sinatra::Base`.
+* You want to use Sinatra only for middleware, and not as an endpoint.
+
+**There is no need to switch to a `config.ru` simply because you
+switched to the modular style, and you don't have to use the modular
+style for running with a `config.ru`.**
+
+### Using Sinatra as Middleware
+
+Not only is Sinatra able to use other Rack middleware, any Sinatra
+application can, in turn, be added in front of any Rack endpoint as
+middleware itself. This endpoint could be another Sinatra application,
+or any other Rack-based application (Rails/Hanami/Roda/...):
+
+```ruby
+require 'sinatra/base'
+
+class LoginScreen < Sinatra::Base
+  enable :sessions
+
+  get('/login') { haml :login }
+
+  post('/login') do
+    if params['name'] == 'admin' && params['password'] == 'admin'
+      session['user_name'] = params['name']
+    else
+      redirect '/login'
+    end
+  end
+end
+
+class MyApp < Sinatra::Base
+  # middleware will run before filters
+  use LoginScreen
+
+  before do
+    unless session['user_name']
+      halt "Access denied, please <a href='/login'>login</a>."
+    end
+  end
+
+  get('/') { "Hello #{session['user_name']}." }
+end
+```
+
+### Dynamic Application Creation
+
+Sometimes you want to create new applications at runtime without having to
+assign them to a constant. You can do this with `Sinatra.new`:
+
+```ruby
+require 'sinatra/base'
+my_app = Sinatra.new { get('/') { "hi" } }
+my_app.run!
+```
+
+It takes the application to inherit from as an optional argument:
+
+```ruby
+# config.ru (run with rackup)
+require 'sinatra/base'
+
+controller = Sinatra.new do
+  enable :logging
+  helpers MyHelpers
+end
+
+map('/a') do
+  run Sinatra.new(controller) { get('/') { 'a' } }
+end
+
+map('/b') do
+  run Sinatra.new(controller) { get('/') { 'b' } }
+end
+```
+
+This is especially useful for testing Sinatra extensions or using Sinatra in
+your own library.
+
+This also makes using Sinatra as middleware extremely easy:
+
+```ruby
+require 'sinatra/base'
+
+use Sinatra do
+  get('/') { ... }
+end
+
+run RailsProject::Application
+```
+
+## Scopes and Binding
+
+The scope you are currently in determines what methods and variables are
+available.
+
+### Application/Class Scope
+
+Every Sinatra application corresponds to a subclass of `Sinatra::Base`.
+If you are using the top-level DSL (`require 'sinatra'`), then this
+class is `Sinatra::Application`, otherwise it is the subclass you
+created explicitly. At the class level, you have methods like `get` or
+`before`, but you cannot access the `request` or `session` objects, as
+there is only a single application class for all requests.
+
+Options created via `set` are methods at class level:
+
+```ruby
+class MyApp < Sinatra::Base
+  # Hey, I'm in the application scope!
+  set :foo, 42
+  foo # => 42
+
+  get '/foo' do
+    # Hey, I'm no longer in the application scope!
+  end
+end
+```
+
+You have the application scope binding inside:
+
+* Your application class body
+* Methods defined by extensions
+* The block passed to `helpers`
+* Procs/blocks used as a value for `set`
+* The block passed to `Sinatra.new`
+
+You can reach the scope object (the class) like this:
+
+* Via the object passed to configure blocks (`configure { |c| ... }`)
+* `settings` from within the request scope
+
+### Request/Instance Scope
+
+For every incoming request, a new instance of your application class is
+created, and all handler blocks run in that scope. From within this scope you
+can access the `request` and `session` objects or call rendering methods like
+`erb` or `haml`. You can access the application scope from within the request
+scope via the `settings` helper:
+
+```ruby
+class MyApp < Sinatra::Base
+  # Hey, I'm in the application scope!
+  get '/define_route/:name' do
+    # Request scope for '/define_route/:name'
+    @value = 42
+
+    settings.get("/#{params['name']}") do
+      # Request scope for "/#{params['name']}"
+      @value # => nil (not the same request)
+    end
+
+    "Route defined!"
+  end
+end
+```
+
+You have the request scope binding inside:
+
+* get, head, post, put, delete, options, patch, link and unlink blocks
+* before and after filters
+* helper methods
+* templates/views
+
+### Delegation Scope
+
+The delegation scope just forwards methods to the class scope. However, it
+does not behave exactly like the class scope, as you do not have the class
+binding. Only methods explicitly marked for delegation are available, and you
+do not share variables/state with the class scope (read: you have a different
+`self`). You can explicitly add method delegations by calling
+`Sinatra::Delegator.delegate :method_name`.
+
+You have the delegate scope binding inside:
+
+* The top-level binding, if you did `require "sinatra"`
+* An object extended with the `Sinatra::Delegator` mixin
+
+Have a look at the code for yourself: here's the
+[Sinatra::Delegator mixin](https://github.com/sinatra/sinatra/blob/ca06364/lib/sinatra/base.rb#L1609-1633)
+being [extending the main object](https://github.com/sinatra/sinatra/blob/ca06364/lib/sinatra/main.rb#L28-30).
+
+## Command Line
+
+Sinatra applications can be run directly:
+
+```shell
+ruby myapp.rb [-h] [-x] [-q] [-e ENVIRONMENT] [-p PORT] [-o HOST] [-s HANDLER]
+```
+
+Options are:
+
+```
+-h # help
+-p # set the port (default is 4567)
+-o # set the host (default is 0.0.0.0)
+-e # set the environment (default is development)
+-s # specify rack server/handler (default is puma)
+-q # turn on quiet mode for server (default is off)
+-x # turn on the mutex lock (default is off)
+```
+
+### Wielowątkowość
+
+_Parafrazując
+[this StackOverflow answer](https://stackoverflow.com/a/6282999/5245129)
+dodane przez Konstantin_
+
+Sinatra nie narzuca żadnego modelu współbieżności, ale pozostawia go w rękach programom obsługi Rack'a (serwerom) takim jak Puma lub WEBrick. Sam Sinatra jest bezpieczny wątkowo, więc nie będzie żadnego problemu, jeśli program obsługi Rack'a używa wielowątkowego modelu współbieżności. Oznaczałoby to, że kiedy uruchamiasz
+serwer, musiałbyś określić poprawną metodę wywołania dla konkretnego modułu obsługi Rack. Poniższy przykład pokazuje, jak uruchomić wielowątkowy Rainbows serwer:
+
+```ruby
+# config.ru
+
+require 'sinatra/base'
+
+class App < Sinatra::Base
+  get '/' do
+    "Witaj świecie"
+  end
+end
+
+run App
+```
+
+```ruby
+# rainbows.conf
+
+# Konfiguracja Rainbows bazuje na Unicorn.
+Rainbows! do
+  use :ThreadSpawn
+end
+```
+
+Aby uruchomić serwer, należy użyć komendy:
+
+```shell
+rainbows -c rainbows.conf
+```
+
+## Wymagania
+
+Podane poniżej wersje są wspierane:
+<dl>
+  <dt>Ruby 2.3</dt>
+  <dd>
+    2.3 jest całkowicie wspierana i polecana. Nie ma żadnych planów, aby wersja została przestała być wspierana.
+  </dd>
+
+  <dt>Rubinius</dt>
+  <dd>
+    Rubinius is officially supported (Rubinius >= 2.x). It is recommended to
+    <tt>gem install puma</tt>.
+  </dd>
+
+  <dt>JRuby</dt>
+  <dd>
+    The latest stable release of JRuby is officially supported. It is not
+    recommended to use C extensions with JRuby. It is recommended to
+    <tt>gem install trinidad</tt>.
+  </dd>
+</dl>
+
+Versions of Ruby before 2.3 are no longer supported as of Sinatra 2.1.0.
+
+We also keep an eye on upcoming Ruby versions.
+
+The following Ruby implementations are not officially supported but still are
+known to run Sinatra:
+
+* Older versions of JRuby and Rubinius
+* Ruby Enterprise Edition
+* MacRuby, Maglev, IronRuby
+* Ruby 1.9.0 and 1.9.1 (but we do recommend against using those)
+
+Not being officially supported means if things only break there and not on a
+supported platform, we assume it's not our issue but theirs.
+
+We also run our CI against ruby-head (future releases of MRI), but we
+can't guarantee anything, since it is constantly moving. Expect upcoming
+2.x releases to be fully supported.
+
+Sinatra should work on any operating system supported by the chosen Ruby
+implementation.
+
+If you run MacRuby, you should `gem install control_tower`.
+
+Sinatra currently doesn't run on Cardinal, SmallRuby, BlueRuby or any
+Ruby version prior to 2.2.
+
+## The Bleeding Edge
+
+If you would like to use Sinatra's latest bleeding-edge code, feel free
+to run your application against the master branch, it should be rather
+stable.
+
+We also push out prerelease gems from time to time, so you can do a
+
+```shell
+gem install sinatra --pre
+```
+
+to get some of the latest features.
+
+### With Bundler
+
+If you want to run your application with the latest Sinatra, using
+[Bundler](https://bundler.io) is the recommended way.
+
+First, install bundler, if you haven't:
+
+```shell
+gem install bundler
+```
+
+Then, in your project directory, create a `Gemfile`:
+
+```ruby
+source 'https://rubygems.org'
+gem 'sinatra', :github => 'sinatra/sinatra'
+
+# other dependencies
+gem 'haml'                    # for instance, if you use haml
+```
+
+Note that you will have to list all your application's dependencies in
+the `Gemfile`. Sinatra's direct dependencies (Rack and Tilt) will,
+however, be automatically fetched and added by Bundler.
+
+Now you can run your app like this:
+
+```shell
+bundle exec ruby myapp.rb
+```
+
+## Versioning
+
+Sinatra follows [Semantic Versioning](https://semver.org/), both SemVer and
+SemVerTag.
+
+## Further Reading
+
+* [Project Website](http://www.sinatrarb.com/) - Additional documentation,
+  news, and links to other resources.
+* [Contributing](http://www.sinatrarb.com/contributing) - Find a bug? Need
+  help? Have a patch?
+* [Issue tracker](https://github.com/sinatra/sinatra/issues)
+* [Twitter](https://twitter.com/sinatra)
+* [Mailing List](https://groups.google.com/forum/#!forum/sinatrarb)
+* IRC: [#sinatra](irc://chat.freenode.net/#sinatra) on [Freenode](https://freenode.net)
+* [Sinatra & Friends](https://sinatrarb.slack.com) on Slack
+  ([get an invite](https://sinatra-slack.herokuapp.com/))
+* [Sinatra Book](https://github.com/sinatra/sinatra-book) - Cookbook Tutorial
+* [Sinatra Recipes](http://recipes.sinatrarb.com/) - Community contributed
+  recipes
+* API documentation for the [latest release](http://www.rubydoc.info/gems/sinatra)
+  or the [current HEAD](http://www.rubydoc.info/github/sinatra/sinatra) on
+  [RubyDoc](http://www.rubydoc.info/)
+* [CI server](https://travis-ci.org/sinatra/sinatra)