Recursively find and print out all subclasses

recursive_find_subclasses.rb

#!/usr/bin/env ruby

# recursively find classes

starting_file, working_directory = *ARGV

throw 'Please specify the file that contains the base class and the source directory' unless starting_file && working_directory

def files_that_subclass(file_path, dir)
  contents = File.read(file_path)
  # expects to find classes defined as "class foo..."
  class_name = contents[/^class ([a-zA-Z0-9]+)\b/, 1]
  # expects to find subclasses defined as "extends foo"
  subclass_regexp = 'extends ' + class_name + '\b'

  subclass_file_paths = `grep --files-with-matches --recursive --exclude-dir=".*" "#{subclass_regexp}" src`.split

  [File.absolute_path(file_path)] + subclass_file_paths.flat_map {|p| files_that_subclass(p, dir)}
end

puts files_that_subclass(starting_file, working_directory).sort