auth.rb

require 'rest-client'
require 'json'

client_id = '42f5e************************'
client_secret = 'secret-b42-************************'

begin 
response = RestClient.post('www.my_app.com/oauth/token', {
  grant_type: 'client_credentials',
  client_id: client_id,
  client_secret: client_secret
}) { |response, request, result|
  case response.code
  when 301, 302, 307
    response.follow_redirection
  else
    response.return!
  end
}
puts response.body

rescue RestClient::ExceptionWithResponse => e
  puts e.response
end

get.rb

require 'rest-client'
require 'json'

access_tokken = "bearer_token_********"
access_tokken = "Bearer #{access_tokken}"

url = "my_secret_ressource_endpoint/31"
response = RestClient.get(url, {
  Authorization: access_tokken
})

puts response.body