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Sinatra

Gem Version Build Status SemVer

Sinatra is a DSL for quickly creating web applications in Ruby with minimal effort:

# myapp.rb
require 'sinatra'

get '/' do 'Hello world!' end

Install the gem:

gem install sinatra

And run with:

ruby myapp.rb

View at: 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.

It is recommended to also run

gem install puma
, which Sinatra will pick up if available.

Table of Contents

Routes

In Sinatra, a route is an HTTP method paired with a URL-matching pattern. Each route is associated with a block:

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:

get '/foo' do
  # Does not match "GET /foo/"
end

Route patterns may include named parameters, accessible via the

params
hash:
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:

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:
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:

get '/download/*.*' do |path, ext|
  [path, ext] # => ["path/to/file", "xml"]
end

Route matching with Regular Expressions:

get /\/hello\/([\w]+)/ do
  "Hello, #{params['captures'].first}!"
end

Or with a block parameter:

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:

get '/posts/:format?' do
  # matches "GET /posts/" and any extension "GET /posts/json", "GET /posts/xml" etc
end

Routes may also utilize query parameters:

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), the request path might be modified before matching against your routes.

You may customize the Mustermann options used for a given route by passing in a

:mustermann_opts
hash:
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, but it isn't one! These options will be merged into the global

:mustermann_opts
hash described below.

Conditions

Routes may include a variety of matching conditions, such as the user agent:

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
:
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:

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:

set(:auth) do |*roles|   #  [: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 any 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:

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) to reduce boiler plate 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:

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:

get // do
  pass if request.path_info == "/index"
  # ...
end

Or, using negative look ahead:

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:
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) to add
Cache-Control
header info.

Views / Templates

Each template language is exposed via its own rendering method. These methods simply return a string:

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:

get '/' do
  code = ""
  erb code
end

Templates take a second argument, the options hash:

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:

get '/' do
  haml :index, :format => :html5
end

You can also set options per template language in general:

set :haml, :format => :html5

get '/' do haml :index end

Options passed to the render method override options set via

set
.

Available Options:

locals
List of locals passed to the document. Handy with partials. Example: erb "", :locals => {:foo => "bar"}
default_encoding
String encoding to use if uncertain. Defaults to settings.default_encoding.
views
Views folder to load templates from. Defaults to settings.views.
layout
Whether to use a layout (true or false). If it's a Symbol, specifies what template to use. Example: erb :index, :layout => !request.xhr?
content_type
Content-Type the template produces. Default depends on template language.
scope
Scope to render template under. Defaults to the application instance. If you change this, instance variables and helper methods will not be available.
layout_engine
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: set :rdoc, :layout_engine => :erb
layout_options
Special options only used for rendering the layout. Example: set :rdoc, :layout_options => { :views => 'views/layouts' }

Templates are assumed to be located directly under the

./views
directory. To use a different views directory:
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

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:
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:

require 'rdiscount' # or require 'bluecloth'
get('/') { markdown :index }

Haml Templates

Dependency haml
File Extension .haml
Example haml :index, :format => :html5

Erb Templates

Dependency erubi or erubis or erb (included in Ruby)
File Extensions .erb, .rhtml or .erubi (Erubi only) or .erubis (Erubis only)
Example erb :index

Builder Templates

Dependency builder
File Extension .builder
Example builder { |xml| xml.em "hi" }

It also takes a block for inline templates (see example).

Nokogiri Templates

Dependency nokogiri
File Extension .nokogiri
Example nokogiri { |xml| xml.em "hi" }

It also takes a block for inline templates (see example).

Sass Templates

Dependency sass
File Extension .sass
Example sass :stylesheet, :style => :expanded

SCSS Templates

Dependency sass
File Extension .scss
Example scss :stylesheet, :style => :expanded

Less Templates

Dependency less
File Extension .less
Example less :stylesheet

Liquid Templates

Dependency liquid
File Extension .liquid
Example liquid :index, :locals => { :key => 'value' }

Since you cannot call Ruby methods (except for

yield
) from a Liquid template, you almost always want to pass locals to it.

Markdown Templates

Dependency Anyone of: RDiscount, RedCarpet, BlueCloth, kramdown, maruku commonmarker pandoc
File Extensions .markdown, .mkd and .md
Example markdown :index, :layout_engine => :erb

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:

erb :overview, :locals => { :text => markdown(:introduction) }

Note that you may also call the

markdown
method from within other templates:
%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

Dependency RedCloth
File Extension .textile
Example textile :index, :layout_engine => :erb

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:

erb :overview, :locals => { :text => textile(:introduction) }

Note that you may also call the

textile
method from within other templates:
%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

Dependency RDoc
File Extension .rdoc
Example rdoc :README, :layout_engine => :erb

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:

erb :overview, :locals => { :text => rdoc(:introduction) }

Note that you may also call the

rdoc
method from within other templates:
%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

Dependency Asciidoctor
File Extension .asciidoc, .adoc and .ad
Example asciidoc :README, :layout_engine => :erb

Since you cannot call Ruby methods directly from an AsciiDoc template, you almost always want to pass locals to it.

Radius Templates

Dependency Radius
File Extension .radius
Example radius :index, :locals => { :key => 'value' }

Since you cannot call Ruby methods directly from a Radius template, you almost always want to pass locals to it.

Markaby Templates

Dependency Markaby
File Extension .mab
Example markaby { h1 "Welcome!" }

It also takes a block for inline templates (see example).

RABL Templates

Dependency Rabl
File Extension .rabl
Example rabl :index

Slim Templates

Dependency Slim Lang
File Extension .slim
Example slim :index

Creole Templates

Dependency Creole
File Extension .creole
Example creole :wiki, :layout_engine => :erb

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:

erb :overview, :locals => { :text => creole(:introduction) }

Note that you may also call the

creole
method from within other templates:
%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

Dependency WikiCloth
File Extension .mediawiki and .mw
Example mediawiki :wiki, :layout_engine => :erb

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:

erb :overview, :locals => { :text => mediawiki(:introduction) }

Note that you may also call the

mediawiki
method from within other templates:
%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

Dependency CoffeeScript and a way to execute javascript
File Extension .coffee
Example coffee :index

Stylus Templates

Dependency Stylus and a way to execute javascript
File Extension .styl
Example stylus :index

Before being able to use Stylus templates, you need to load

stylus
and
stylus/tilt
first:
require 'sinatra'
require 'stylus'
require 'stylus/tilt'

get '/' do stylus :example end

Yajl Templates

Dependency yajl-ruby
File Extension .yajl
Example yajl :index, :locals => { :key => 'qux' }, :callback => 'present', :variable => 'resource'

The template source is evaluated as a Ruby string, and the resulting json variable is converted using

#to_json
:
json = { :foo => 'bar' }
json[:baz] = key

The

:callback
and
:variable
options can be used to decorate the rendered object:
var resource = {"foo":"bar","baz":"qux"};
present(resource);

WLang Templates

Dependency WLang
File Extension .wlang
Example wlang :index, :locals => { :key => 'value' }

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:

get '/:id' do
  @foo = Foo.find(params['id'])
  haml '%h1= @foo.name'
end

Or, specify an explicit Hash of local variables:

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:
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:

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:

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:

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:
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
:
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:
Tilt.register :tt, Tilt[:textile]

Adding Your Own Template Engine

First, register your engine with Tilt, then create a rendering method:

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.

Using Custom Logic for Template Lookup

To implement your own template lookup mechanism you can write your own

#find_template
method:
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:

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:

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:

before '/protected/*' do
  authenticate!
end

after '/create/:slug' do |slug| session[:last_slug] = slug end

Like routes, filters also take conditions:

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:
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:

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:

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 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

$ ruby -e "require 'securerandom'; puts SecureRandom.hex(64)"
99ae8af...snip...ec0f262ac

Session Secret Generation (Bonus Points)

Use the sysrandom gem to prefer use of system RNG facilities to generate random values instead of userspace

OpenSSL
which MRI Ruby currently defaults to:
$ 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:
# echo "export SESSION_SECRET=99ae8af...snip...ec0f262ac" >> ~/.bashrc

Session Secret App Config

Setup 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 here as well:

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:
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:

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:
enable :sessions
set :session_store, Rack::Session::Pool

Or to set up sessions with a hash of options:

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:

use Rack::Session::Pool, :expire_after => 2592000
use Rack::Protection::RemoteToken
use Rack::Protection::SessionHijacking

See 'Configuring attack protection' for more information.

Halting

To immediately stop a request within a filter or route use:

halt

You can also specify the status when halting:

halt 410

Or the body:

halt 'this will be the body'

Or both:

halt 401, 'go away!'

With headers:

halt 402, {'Content-Type' => 'text/plain'}, 'revenge'

It is of course possible to combine a template with

halt
:
halt erb(:error)

Passing

A route can punt processing to the next matching route using

pass
:
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:
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 there on to access the body:
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").

Similar to the body, you can also set the status code and headers:

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 tea pot!"
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:
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, and can be used as the basis for WebSockets. 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 web server 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:
# config.ru
require 'sinatra/base'

class App < Sinatra::Base connections = []

get '/subscribe' 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 '/:message' do connections.each do |out| # notify client that a new message has arrived out << params['message'] << "\n"

  # indicate client to connect again
  out.close
end

# acknowledge
"message received"

end end

run App

# rainbows.conf
Rainbows! do
  use :EventMachine
end

Run:

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:
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:
class MyApp < Sinatra::Base
  configure :production, :development do
    enable :logging
  end
end

To avoid any logging middleware to be set up, set the

logging
setting 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:
configure do
  mime_type :foo, 'text/foo'
end

You can also use it with the

content_type
helper:
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:
%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 for an example).

Browser Redirect

You can trigger a browser redirect with the

redirect
helper method:
get '/foo' do
  redirect to('/bar')
end

Any additional parameters are handled like arguments passed to

halt
:
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
:
get '/foo' do
  "do something"
end

get '/bar' do do_something redirect back end

To pass arguments with a redirect, either add them to the query:

redirect to('/bar?sum=42')

Or use a session:

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:

get '/' do
  cache_control :public
  "cache it!"
end

Pro tip: Set up caching in a before filter:

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:
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:
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:

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:

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) 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:
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:
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:
get '/' do
  send_file 'foo.png'
end

It also takes options:

send_file 'foo.png', :type => :jpg

The options are:

filename
File name to be used in the response, defaults to the real file name.
last_modified
Value for Last-Modified header, defaults to the file's mtime.
type
Value for Content-Type header, guessed from the file extension if missing.
disposition
Value for Content-Disposition header, possible values: nil (default), :attachment and :inline
length
Value for Content-Length header, defaults to file size.
status
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.

Accessing the Request Object

The incoming request object can be accessed from request level (filter, routes, error handlers) through the

request
method:
# 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:
before { request.path_info = "/" }

get "/" do "all requests end up here" end

The

request.body
is an IO or StringIO object:
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:
get '/' do
  attachment
  "store it!"
end

You can also pass it a file name:

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:
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:
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:
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:

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:

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 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:

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
:
configure :production do
  ...
end

Run when the environment is set to either

:production
or
:test
:
configure :production, :test do
  ...
end

You can access those options via

settings
:
configure do
  set :foo, 'bar'
end

get '/' do settings.foo? # => true settings.foo # => 'bar' ... end

Configuring attack protection

Sinatra is using Rack::Protection 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):

disable :protection

To skip a single defense layer, set

protection
to an options hash:
set :protection, :except => :path_traversal

You can also hand in an array in order to disable a list of protections:

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'. 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:
set :protection, :session => true

Available Settings

absolute_redirects
If disabled, Sinatra will allow relative redirects, however, Sinatra will no longer conform with RFC 2616 (HTTP 1.1), which only allows absolute redirects.
Enable if your app is running behind a reverse proxy that has not been set up properly. Note that the url helper will still produce absolute URLs, unless you pass in false as the second parameter.
Disabled by default.
add_charset
Mime types the content_type helper will automatically add the charset info to. You should add to it rather than overriding this option: settings.add_charset << "application/foobar"
app_file
Path to the main application file, used to detect project root, views and public folder and inline templates.
bind
IP address to bind to (default: 0.0.0.0 or localhost if your `environment` is set to development). Only used for built-in server.
default_content_type
Content-Type to assume if unknown (defaults to "text/html"). Set to nil 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 nosniff is enabled in Rack::Protection::XSSHeader, assume application/octet-stream).
default_encoding
Encoding to assume if unknown (defaults to "utf-8").
dump_errors
Display errors in the log.
environment
Current environment. Defaults to ENV['APP_ENV'], or "development" if not available.
logging
Use the logger.
lock
Places a lock around every request, only running processing on request per Ruby process concurrently.
Enabled if your app is not thread-safe. Disabled by default.
method_override
Use _method magic to allow put/delete forms in browsers that don't support it.
mustermann_opts
A default hash of options to pass to Mustermann.new when compiling routing paths.
port
Port to listen on. Only used for built-in server.
prefixed_redirects
Whether or not to insert request.script_name into redirects if no absolute path is given. That way redirect '/foo' would behave like redirect to('/foo'). Disabled by default.
protection
Whether or not to enable web attack protections. See protection section above.
public_dir
Alias for public_folder. See below.
public_folder
Path to the folder public files are served from. Only used if static file serving is enabled (see static setting below). Inferred from app_file setting if not set.
quiet
Disables logs generated by Sinatra's start and stop commands. false by default.
reload_templates
Whether or not to reload templates between requests. Enabled in development mode.
root
Path to project root folder. Inferred from app_file setting if not set.
raise_errors
Raise exceptions (will stop application). Enabled by default when environment is set to "test", disabled otherwise.
run
If enabled, Sinatra will handle starting the web server. Do not enable if using rackup or other means.
running
Is the built-in server running now? Do not change this setting!
server
Server or list of servers to use for built-in server. Order indicates priority, default depends on Ruby implementation.
server_settings
If you are using a WEBrick web server, presumably for your development environment, you can pass a hash of options to server_settings, such as SSLEnable or SSLVerifyClient. However, web servers such as Puma do not support this, so you can set server_settings by defining it as a method when you call configure.
sessions
Enable cookie-based sessions support using Rack::Session::Cookie. See 'Using Sessions' section for more information.
session_store
The Rack session middleware used. Defaults to Rack::Session::Cookie. See 'Using Sessions' section for more information.
show_exceptions
Show a stack trace in the browser when an exception happens. Enabled by default when environment is set to "development", disabled otherwise.
Can also be set to :after_handler to trigger app-specified error handling before showing a stack trace in the browser.
static
Whether Sinatra should handle serving static files.
Disable when using a server able to do this on its own.
Disabling will boost performance.
Enabled by default in classic style, disabled for modular apps.
static_cache_control
When Sinatra is serving static files, set this to add Cache-Control headers to the responses. Uses the cache_control helper. Disabled by default.
Use an explicit array when setting multiple values: set :static_cache_control, [:public, :max_age => 300]
threaded
If set to true, will tell server to use EventMachine.defer for processing the request.
traps
Whether Sinatra should handle system signals.
views
Path to the views folder. Inferred from app_file setting if not set.
x_cascade
Whether or not to set the X-Cascade header if no route matches. Defaults to true.

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:
APP_ENV=production ruby my_app.rb

You can use predefined methods:

development?
,
test?
and
production?
to check the current environment setting:
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:
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
:
set :show_exceptions, :after_handler

The exception object can be obtained from the

sinatra.error
Rack variable:
error do
  'Sorry there was a nasty error - ' + env['sinatra.error'].message
end

Custom errors:

error MyCustomError do
  'So what happened was...' + env['sinatra.error'].message
end

Then, if this happens:

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:

error 403 do
  'Access forbidden'
end

get '/secret' do 403 end

Or a range:

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, 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:
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 DSL (most frequently used from rackup files). For example, the
use
method accepts multiple/variable args as well as blocks:
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, rack-contrib, or in the Rack wiki.

Testing

Sinatra tests can be written using any Rack-based testing library or framework. Rack::Test is recommended:

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:
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 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
:
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 the classic styles.

If switching from one style to the other, you should be aware of slightly different default settings:

Setting Classic Modular Modular
app_file file loading sinatra file subclassing Sinatra::Base file subclassing Sinatra::Application
run $0 == app_file false false
logging true false true
method_override true false true
inline_templates true false true
static true File.exist?(public_folder) true

Serving a Modular Application

There are two common options for starting a modular app, actively starting with

run!
:
# 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:

ruby my_app.rb

Or with a

config.ru
file, which allows using any Rack handler:
# config.ru (run with rackup)
require './my_app'
run MyApp

Run:

rackup -p 4567

Using a Classic Style Application with a config.ru

Write your app file:

# app.rb
require 'sinatra'

get '/' do 'Hello world!' end

And a corresponding

config.ru
:
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/...):

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 login." 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
:
require 'sinatra/base'
my_app = Sinatra.new { get('/') { "hi" } }
my_app.run!

It takes the application to inherit from as an optional argument:

# 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:

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 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:
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 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:
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 # =&gt; 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 being extending the main object.

Command Line

Sinatra applications can be run directly:

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)

Multi-threading

Paraphrasing from this StackOverflow answer by Konstantin

Sinatra doesn't impose any concurrency model, but leaves that to the underlying Rack handler (server) like Puma or WEBrick. Sinatra itself is thread-safe, so there won't be any problem if the Rack handler uses a threaded model of concurrency. This would mean that when starting the server, you'd have to specify the correct invocation method for the specific Rack handler. The following example is a demonstration of how to start a multi-threaded Rainbows server:

# config.ru

require 'sinatra/base'

class App < Sinatra::Base get '/' do "Hello, World" end end

run App

# rainbows.conf

Rainbows configurator is based on Unicorn.

Rainbows! do use :ThreadSpawn end

To start the server, the command would be:

rainbows -c rainbows.conf

Requirement

The following Ruby versions are officially supported:

Ruby 2.3
2.3 is fully supported and recommended. There are currently no plans to drop official support for it.

Rubinius
Rubinius is officially supported (Rubinius >= 2.x). It is recommended to gem install puma.

JRuby
The latest stable release of JRuby is officially supported. It is not recommended to use C extensions with JRuby. It is recommended to gem install trinidad.

Versions of Ruby prior to 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

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 is the recommended way.

First, install bundler, if you haven't:

gem install bundler

Then, in your project directory, create a

Gemfile
:
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:

bundle exec ruby myapp.rb

Versioning

Sinatra follows Semantic Versioning, both SemVer and SemVerTag.

Further Reading

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