Generate random valid CPFs

cpf.rb

#! /usr/bin/env ruby

# Setup initial variables
number = Random.new
cpf = []
vd1 = 0
vd2 = 0

# Generate the 9 first numbers
1.upto(9) do |i|
  n = number.rand(0..9)
  cpf << n
  # start calculating the Verification Digits (VD)
  vd1 += n * (11 - i)
  vd2 += n * (12 - i)
end

# Calculate the first VD
vd1 = vd1 % 11
vd1 = vd1 < 2 ? 0 : 11 - vd1

# Add first VD to second VD
vd2 += vd1 * 2

# Calculate second VD
vd2 = vd2 % 11
vd2 = vd2 < 2 ? 0 : 11 - vd2

# Add VDs to CPF
cpf << vd1
cpf << vd2

# Print the new cpf
puts cpf.join