man Gemfile (5): A format for describing gem dependencies for Ruby programs

SYNOPSIS

A Gemfile describes the gem dependencies required to execute associated Ruby code.

Place the Gemfile in the root of the directory containing the associated code. For instance, in a Rails application, place the Gemfile in the same directory as the Rakefile.

SYNTAX

A Gemfile is evaluated as Ruby code, in a context which makes available a number of methods used to describe the gem requirements.

SOURCES (#source)

At the top of the Gemfile, add one line for each Rubygems source that might contain the gems listed in the Gemfile.

source "http://rubygems.org"
source "http://gems.github.com"

Each of these _source_s MUST be a valid Rubygems repository.

GEMS (#gem)

Specify gem requirements using the gem method, with the following arguments. All parameters are OPTIONAL unless otherwise specified.

NAME (required)

For each gem requirement, list a single gem line.

gem "nokogiri"

VERSION

Each gem MAY have one or more version specifiers.

gem "nokogiri", ">= 1.4.2"
gem "RedCloth", ">= 4.1.0", "< 4.2.0"

REQUIRE AS (:require)

Each gem MAY specify files that should be used when autorequiring via Bundler.require. You may pass an array with multiple files, or false to prevent any file from being autorequired.

gem "sqlite3-ruby", :require => "sqlite3"
gem "redis", :require => ["redis/connection/hiredis", "redis"]
gem "webmock", :require => false

The argument defaults to the name of the gem. For example, these are identical:

gem "nokogiri"
gem "nokogiri", :require => "nokogiri"

GROUPS (:group or :groups)

Each gem MAY specify membership in one or more groups. Any gem that does not specify membership in any group is placed in the default group.

gem "rspec", :group => :test
gem "wirble", :groups => [:development, :test]

The Bundler runtime allows its two main methods, Bundler.setup and Bundler.require, to limit their impact to particular groups.

# setup adds gems to Ruby's load path
Bundler.setup                    # defaults to all groups
require "bundler/setup"          # same as Bundler.setup
Bundler.setup(:default)          # only set up the _default_ group
Bundler.setup(:test)             # only set up the _test_ group (but `not` _default_)
Bundler.setup(:default, :test)   # set up the _default_ and _test_ groups, but no others
# require requires all of the gems in the specified groups
Bundler.require                  # defaults to just the _default_ group
Bundler.require(:default)        # identical
Bundler.require(:default, :test) # requires the _default_ and _test_ groups
Bundler.require(:test)           # requires just the _test_ group

The Bundler CLI allows you to specify a list of groups whose gems bundle install should not install with the --without option. To specify multiple groups to ignore, specify a list of groups separated by spaces.

bundle install --without test
bundle install --without development test

After running bundle install --without test, bundler will remember that you excluded the test group in the last installation. The next time you run bundle install, without any --without option, bundler will recall it.

Also, calling Bundler.setup with no parameters, or calling require "bundler/setup" will setup all groups except for the ones you excluded via --without (since they are obviously not available).

Note that on bundle install, bundler downloads and evaluates all gems, in order to create a single canonical list of all of the required gems and their dependencies. This means that you cannot list different versions of the same gems in different groups. For more details, see Understanding Bundler http://gembundler.com/rationale.html.

PLATFORMS (:platforms)

If a gem should only be used in a particular platform or set of platforms, you can specify them. Platforms are essentially identical to groups, except that you do not need to use the --without install-time flag to exclude groups of gems for other platforms.

There are a number of Gemfile platforms:

ruby: C Ruby (MRI) or Rubinius, but NOT Windows
ruby_18: ruby AND version 1.8
ruby_19: ruby AND version 1.9
mri: Same as ruby, but not Rubinius
mri_18: mri AND version 1.8
mri_19: mri AND version 1.9
rbx: Same as ruby, but only Rubinius (not MRI)
jruby: JRuby
mswin: Windows
mingw: Windows 'mingw32' platform (aka RubyInstaller)
mingw_18: mingw AND version 1.8
mingw_19: mingw AND version 1.9

As with groups, you can specify one or more platforms:

gem "weakling",   :platforms => :jruby
gem "ruby-debug", :platforms => :mri_18
gem "nokogiri",   :platforms => [:mri_18, :jruby]

All operations involving groups (bundle install, Bundler.setup, Bundler.require) behave exactly the same as if any groups not matching the current platform were explicitly excluded.

GIT (:git)

If necessary, you can specify that a gem is located at a particular git repository. The repository can be public (http://github.com/rails/rails.git) or private ([email protected]:rails/rails.git). If the repository is private, the user that you use to run bundle install MUST have the appropriate keys available in their $HOME/.ssh.

Git repositories are specified using the :git parameter. The group, platforms, and require options are available and behave exactly the same as they would for a normal gem.

gem "rails", :git => "git://github.com/rails/rails.git"

A git repository SHOULD have at least one file, at the root of the directory containing the gem, with the extension .gemspec. This file MUST contain a valid gem specification, as expected by the gem build command. It MUST NOT have any dependencies, other than on the files in the git repository itself and any built-in functionality of Ruby or Rubygems.

If a git repository does not have a .gemspec, bundler will attempt to create one, but it will not contain any dependencies, executables, or C extension compilation instructions. As a result, it may fail to properly integrate into your application.

If a git repository does have a .gemspec for the gem you attached it to, a version specifier, if provided, means that the git repository is only valid if the .gemspec specifies a version matching the version specifier. If not, bundler will print a warning.

gem "rails", "2.3.8", :git => "git://github.com/rails/rails.git"
# bundle install will fail, because the .gemspec in the rails
# repository's master branch specifies version 3.0.0

If a git repository does not have a .gemspec for the gem you attached it to, a version specifier MUST be provided. Bundler will use this version in the simple .gemspec it creates.

Git repositories support a number of additional options.

branch, tag, and ref: You MUST only specify at most one of these options. The default is :branch => "master"
submodules: Specify :submodules => true to cause bundler to expand any submodules included in the git repository

If a git repository contains multiple .gemspecs, each .gemspec represents a gem located at the same place in the file system as the .gemspec.

|~rails                   [git root]
| |-rails.gemspec         [rails gem located here]
|~actionpack
| |-actionpack.gemspec    [actionpack gem located here]
|~activesupport
| |-activesupport.gemspec [activesupport gem located here]
|...

To install a gem located in a git repository, bundler changes to the directory containing the gemspec, runs gem build name.gemspec and then installs the resulting gem. The gem build command, which comes standard with Rubygems, evaluates the .gemspec in the context of the directory in which it is located.

PATH (:path)

You can specify that a gem is located in a particular location on the file system. Relative paths are resolved relative to the directory containing the Gemfile.

Similar to the semantics of the :git option, the :path option requires that the directory in question either contains a .gemspec for the gem, or that you specify an explicit version that bundler should use.

Unlike :git, bundler does not compile C extensions for gems specified as paths.

gem "rails", :path => "vendor/rails"

BLOCK FORM OF GIT, PATH, GROUP and PLATFORMS

The :git, :path, :group, and :platforms options may be applied to a group of gems by using block form.

git "git://github.com/rails/rails.git" do
  gem "activesupport"
  gem "actionpack"
end
platforms :ruby do
  gem "ruby-debug"
  gem "sqlite3-ruby"
end
group :development do
  gem "wirble"
  gem "faker"
end

In the case of the git block form, the :ref, :branch, :tag, and :submodules options may be passed to the git method, and all gems in the block will inherit those options.

GEMSPEC (#gemspec)

If you wish to use Bundler to help install dependencies for a gem while it is being developed, use the gemspec method to pull in the dependencies listed in the .gemspec file.

The gemspec method adds any runtime dependencies as gem requirements in the default group. It also adds development dependencies as gem requirements in the development group. Finally, it adds a gem requirement on your project (:path => '.'). In conjunction with Bundler.setup, this allows you to require project files in your test code as you would if the project were installed as a gem; you need not manipulate the load path manually or require project files via relative paths.

The gemspec method supports optional :path, :name, and :development_group options, which control where bundler looks for the .gemspec, what named .gemspec it uses (if more than one is present), and which group development dependencies are included in.

SOURCE PRIORITY

When attempting to locate a gem to satisfy a gem requirement, bundler uses the following priority order:

1.

The source explicitly attached to the gem (using :path or :git)

2.

For implicit gems (dependencies of explicit gems), any git or path repository otherwise declared. This results in bundler prioritizing the ActiveSupport gem from the Rails git repository over ones from rubygems.org

3.

The sources specified via source, searching each source in your Gemfile from last added to first added.