user.gemspec The gemspec defines what's in the gem, who made it, and the version of gem. It's also your interface to RubyGems.org

Gem::Specification.new do |s|
s.name        = "user_greeting"
s.version     = "0.0.1"
s.summary     = "User Greeting"
s.description = "Greet the user!"
s.authors     = ["Bikash Shrestha"]
s.email       = "[email protected]"
s.files       = Dir["lib/*.rb"]
s.homepage    = "https://rubygems.org/gems/user_greeting"
s.license     = "MIT"
end

lib/user.rb

class User
  def self.greet name
     puts "Hello, #{name}"
  end
end

.
├── lib
│   └── user.rb
├── .ruby-version
└── user.gemspec

rbenv local 3.1.2 -> this creates .ruby-version file

After you've created a gemspec, you can build a ruby gem from it. Then you can install the generated gem locally to test it out.

To build gem run: gem build user.gemspec

To install gem run: gem install user_greeting-0.0.1.gem

Of course, the smoke test isn't over yet: the final step is to require the gem and use it:

$ irb
irb(main):004:0> require "user"
=> false
irb(main):005:0> User.greet "Bikash Shrestha"
Hello, Bikash Shrestha
=> nil

To publish your gem, you'll need to create an account on RubyGems.org.

After creating an account, you can push your gem to RubyGems.org using the following commands:

Sign in using gem signin (this will ask your email/username and password on command prompt)

gem push user_greeting-0.0.1.gem

Install your gem : gem install user_greeting

Ruby Gem Basics

Specification Ref.

Publish your first ruby gem

Crafting and Publishing Your Ruby Gem

RubyMine: Create & Publish your first Ruby gem

Lunch your own Ruby gem

A step by step guide for building ruby gem