Detect invalid characters in a CSV

detect.rb

contents = File.read('/Users/Josh/Desktop/1.csv')

unless contents.valid_encoding?
  invalid_characters = {}

  contents.each_line.with_index do |line, idx|
    invalid_characters[idx] ||= []

    line.each_char do |char|
      unless char.valid_encoding?
        invalid_characters[idx] << char
      end
    end
  end

  invalid_characters.select!{ |_line, characters| characters.any? }

  invalid_characters.each do |line, characters|
    if characters.any?
      puts "Line #{line}: #{characters.join(',')}"
    end
  end
end