A simple Ruby utility to validate and generate Luhn-compliant numbers.

luhn_util is able to:

• Validate an input according to the Luhn algorithm
• Calculate the check digit for a given numeric input
• Generate random Luhn number based on any valid length and prefix

The algorithm followed is based on Luhn Algorithm.

Install the gem and add to the application's Gemfile by executing:

bundle add luhn_util

If bundler is not being used to manage dependencies, install the gem by executing:

gem install luhn_util

Require the file:

require 'luhn'

To check if input is valid:

$ Luhn.valid?('5185443765446305')
$ true

To calculate the check digit:

$ Luhn.check_digit('1234567890')
$ 3

The generate method returns a 16-character number by default:

$ Luhn.generate
$ 5185443765446305

Length may also be specified:

$ Luhn.generate(length: 8)
$ 29974938

Prefix may also be supplied:

$ Luhn.generate(prefix: '88')
$ 8821951428417137

$ Luhn.generate(length: 8, prefix: '88')
$ 88405022

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/katpadi/luhn_util. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the luhn_util project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.