Access variables defined in _config.yml within Jekyll Hook

Question

How can one access site variables (i.e. variables defined in _config.yml) from within a Jekyll::Hooks plugin?

I thought site.variable would do it but this raises:

Error:  undefined local variable or method `site' for main:Object

Answer 1

Aha, one has to pass the site variable into the hook itself:

Jekyll::Hooks.register :site, :post_write do |site|
  if site.config['create_index']
    system('npm run index')
  end
end