RubyでShift_JISの範囲に収まっていない文字を見える化したい

pickout-damemoji.rb

  begin
    open(f, 'rb:Shift_JIS:UTF-8').read
  rescue Encoding::UndefinedConversionError => e
    fulltilde = "\x81\x60".force_encoding("Windows-31J")
    tmptab    = "\v".force_encoding("Windows-31J")

    w = open(f, 'rb:Windows-31J').read.gsub(fulltilde, tmptab)

    s = w.encode('Shift_JIS', undef: :replace, replace: '??'.colorize(:magenta))
    diff = s.encode('Windows-31J', undef: :replace, replace: '??'.colorize(:magenta)).lines - w.lines

    if diff.size > 0
      puts ""
      puts f

      puts diff.map {|e| e.gsub(tmptab, fulltilde).encode('UTF-8')}
    end
  end

colorize は https://github.com/fazibear/colorize です