After Facebook & Twitter share ,its time for Linkedin. I would suggest you to refer my 2 prev posts before going through this article.
Include "linkedin" gem in your Gemfile and bundle .
gem 'linkedin'
Route file:
match '/linkedin_share/auth' => 'linkedin_share#auth' , :method => :get , :as => :linkedin_auth match '/linkedin_share/callback' => 'linkedin_share#callback' , :method => :get , :as => :linkedin_callback