Where is the source for rails command line like new, generate located?

I would like to know when we run commands like rails new, rails generate. Which files are actually executed. In general for other tools like rake, rspec( not sure they are called command line tools ) or any other such gem, which files are executed first( at the beginning ). Thanks.

Most of them are located in this folder https://github.com/rails/rails/tree/3be590edbedab8ddcacdf72790d50c3cf9354434/railties/lib/rails/commands

For instance this https://github.com/rails/rails/blob/3be590edbedab8ddcacdf72790d50c3cf9354434/railties/lib/rails/commands/application/application_command.rb calls the app generator https://github.com/rails/rails/blob/3be590edbedab8ddcacdf72790d50c3cf9354434/railties/lib/rails/generators/rails/app/app_generator.rb