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A fast Gherkin parser in Ragel (The parser behind Cucumber)
Ruby Java JavaScript Other
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A fast lexer and parser for the Gherkin language based on Ragel. Gherkin is two things:

  • The language that has evolved out of the Cucumber project.
  • This library.

Supported platforms:

  • Ruby 1.8.7-1.9.3 (MRI, JRuby, REE, Rubinius)
  • Pure Java (jar file)
  • JavaScript (Tested with V8/node.js/Chrome, but might work on other JavaScript engines)
  • .NET (dll file)



gem install gherkin


On JRuby you may get an error saying:

ERROR:  While executing gem ... (ArgumentError)
undefined class/module YAML::Syck::DefaultKey

You can get around this problem by upgrading rubygems:

jruby -S gem install rubygems-update
gem update --system

Another problem you might encounter is:

ERROR: While executing gem ... (ArgumentError)
invalid byte sequence in US-ASCII

If this happens, try defining your shell's encoding:

# Linux
export LANG=en_US.UTF-8

# OS X
export LC_CTYPE=en_US.UTF-8


npm install gherkin


The jar file is in the central Maven repo.


You can get it manually from Maven Central


Get the dll from NuGet

API Docs

Hacking: Installing the toolchain

Due to the cross-platform nature of this library, you have to install a lot of tools to build gherkin yourself. In order to make it easier for occasional contributors to get the development environment up and running, you don't have to install everything up front. The build scripts should tell you if you are missing something. For example, you shouldn't have to install MinGW to build windows binaries if you are a Linux user and just want to fix a bug in the C code.

Common dependencies

These are the minimal tools you need to install:

  • Ragel (brew install ragel or apt-get install ragel)
  • Ruby (any version should do).
  • A clone of the cucumber git repo to a "cucumber" sibling folder of your gherkin folder. (Only needed to run cucumber tests)
  • RVM (you may not need this if you are only building for a single platform)

With this minimal tool chain installed, install Ruby gems needed by the build:

gem install bundler
bundle install

Running RSpec and Cucumber tests

rake clean spec cucumber

If the RL_LANGS environment variable is set, only the parsers for the languages specified there will be built. E.g. in Bash, export RL_LANGS="en,fr,no". This can be quite helpful when modifying the Ragel grammar.

See subsections for building for a specific platform.

MRI, REE or Rubinius

You'll need GCC installed.

Build the gem with:

rake build

Pure Java and JRuby

You must install JRuby to build the pure Java jar or the JRuby gem:

rvm install jruby
rvm use jruby
rvm gemset create cucumber
rvm gemset use cucumber
gem install bundler
bundle install

Now you can build the jar with:

rake clean jar


In order to build and test Gherkin for JavaScript you must install:

  • Node.js (0.6.17 or higher with npm)
  • Ragel with JavaScript support:
    • Make sure you have autoconf and automake (brew install automake)
    • Make sure you have the official ragel (brew install ragel)
    • Make sure you have kelbt (brew install kelbt). If that fails, install manually from
    • cd ragel-js/ragel-svn && ./ && ./configure --disable-manual
    • make && make install
  • Define the GHERKIN_JS environment variable in your shell (any value will do)

Now you can build the JavaScript with:

rake js

And you can try it out with node.js:

node js/example/print.js spec/gherkin/fixtures/1.feature

Or the json formatter:

node js/example/json_fomratter_example.js

If you're hacking and just want to rebuild the English parser:

rake js/lib/gherkin/lexer/en.js

In order to test the native JavaScript implementation of JSONFormatter, you also need to define the GHERKIN_JS_NATIVE environment variable. It's recommended you don't do this permanently, as it will disable testing the Ruby implementation. Try this instead:

GHERKIN_JS_NATIVE=true GHERKIN_JS=true bundle exec rake

TODO: Make all specs pass with js lexer - replace 'c(listener)' with 'js(listener)' in i18n.rb

.NET dll

You must install Mono SDK 2.10.8. The OS X package installer is not recommended as it modifies your system PATH and makes Homebrew unhappy. Install with homebrew instead:

brew install ikvm/mono.rb

You must also download NuGet.exe from CodePlex and place it in /usr/local/nuget/NuGet.exe. When it's installed, update it and register your NuGet API Key:

# In case we need to update
mono /usr/local/nuget/NuGet.exe Update -self

# The key is at
mono --runtime=v4.0.30319 /usr/local/nuget/NuGet.exe SetApiKey xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx

Now you can build the .NET dll with:

mkdir release
rake ikvm
rake release/nuspec/lib/gherkin.dll

This should build release/nuspec/lib/gherkin.dll

MinGW Rubies (for Windows gems)

In order to build Windows binaries (so we can release Windows gems from OS X/Linux) we first need to install MinGW:


Now, make sure you have openssl installed - it's needed to build the rubies.

brew install openssl

Next, we're going to install Ruby 1.8.7 and Ruby 1.9.3 for MinGW. We need both versions so we can build Windows binaries for both. OS X Lion (or later) doesn't ship with an LLVM free gcc, which you will need in order to install ruby 1.8.7. We can install it with:

brew install

For more info see:

Now we're ready to install the Windows rubies:


# 1.9.3
rvm install 1.9.3-p194
rvm use 1.9.3-p194
rvm gemset create cucumber
rvm gemset use cucumber
gem install bundler
bundle install
PATH=/usr/local/mingw/bin:$PATH CC=/usr/local/mingw/bin/i686-w64-mingw32-gcc rake-compiler cross-ruby VERSION=1.9.3-p194

# 1.8.7
CC=gcc-4.2 rvm install 1.8.7-p352
rvm use 1.8.7-p352
rvm gemset create cucumber
rvm gemset use cucumber
gem install bundler
bundle install
PATH=/usr/local/mingw/bin:$PATH CC=/usr/local/mingw/bin/i686-w64-mingw32-gcc rake-compiler cross-ruby VERSION=1.8.7-p352

Now you can build Windows gems:

rake compile
mkdir release
rake gems:win

Release process

Make sure you have access to all the servers where packages are being uploaded:

  • npm registry: npm login
  • gem push
  • ssh
  • sonatype: Check ~/.m2/settings.xml and that you have gnupg (OS X users: Install GPGTools)
  • nuget: See .NET section above

Run tests once with GHERKIN_JS_NATIVE=true:

GHERKIN_JS_NATIVE=true GHERKIN_JS=true bundle exec rake

Now we can release:

  • Make sure GHERKIN_JS is defined (see JavaScript section above)
  • Bump version in:
    • This file (Installation/Java section)
    • gherkin.gemspec
    • java/pom.xml
    • js/package.json
  • Run bundle update, so Gemfile.lock gets updated with the changes.
  • Commit changes, otherwise you will get an error at the end when a tag is made.
  • Run bundle exec rake gems:prepare && ./ && bundle exec rake release:ALL

Note on Patches/Pull Requests

  • Fork the project.
  • Run rake ragel:rb to generate all the I18n lexers
  • Make your feature addition or bug fix.
  • Add tests for it. This is important so I don't break it in a future version unintentionally.
  • Commit, do not mess with Rakefile, VERSION, or History.txt. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
  • Send me a pull request. Bonus points for topic branches.


Copyright (c) 2009-2012 Mike Sassak, Gregory Hnatiuk, Aslak Hellesøy. See LICENSE for details.

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