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RuboCop is a Ruby code style checker based on the Ruby Style Guide.


RuboCop's installation is pretty standard:

$ gem install rubocop

Basic Usage

Running rubocop with no arguments will check all Ruby source files in the current folder:

$ rubocop

Alternatively you can rubocop a list of files and folders to check:

$ rubocop app spec lib/something.rb

For more details check the available command-line options:

$ rubocop -h
Command flag Description
-v/--version Displays the current version and exits
-d/--debug Displays some extra debug output
-e/--emacs Output the results in Emacs format
-c/--config Run with specified config file
-s/--silent Suppress the final summary


The behavior of RuboCop can be controlled via the .rubocop.yml configuration file. The file can be placed either in your home folder or in some project folder.

RuboCop will start looking for the configuration file in the directory it was started in and continue its way up to the home folder.

The file has the following format:

  Enabled: true

  Enabled: true
  Max: 79

It allows to enable/disable certain cops (checks) and to alter their behavior if they accept any parameters.


Unfortunately every major Ruby implementation has its own code analysis tooling, which makes the development of a portable code analyzer a daunting task.

RuboCop currently supports MRI 1.9 and MRI 2.0. Support for JRuby and Rubinius is not planned at this point.

Copyright (c) 2012-2013 Bozhidar Batsov. See LICENSE.txt for further details.