How to call a non-class function from a class method?

Question

I'm trying to call the sh method from FileUtils.

class A
  def self.method
    sh('echo hello')
  end
end

def function
  sh('echo hello')
end

function # this is fine
A.method # this gives an error

The error I get is NoMethodError: undefined method 'sh' for A:Class How can I change my method to be able to call the function?