def backward_lines(size = 10)

      file   = @file
      reg    = Regexp.new('\r\n|\r|\n')
      result = ""

      while file.pos > 0

        char = backward_char

        if char.nil?
          file.rewind
          break
        end

        # backward pos as bytesize of char
        file.seek(-(char.bytesize), IO::SEEK_CUR)

        break if char.match(reg) && result.scan(reg).size > size

        result.insert(0, char)
      end

      result
    end
def backward_lines(size = 10)

      file   = @file
      reg    = Regexp.new('\r\n|\r|\n')
      result = ""

      while file.pos > 0

        char = backward_char

        if char.nil?
          file.rewind
          break
        end

        # backward pos as bytesize of char
        file.seek(-(char.bytesize), IO::SEEK_CUR)

        break if char.match(reg) && result.scan(reg).size > size

        result.insert(0, char)
      end

      result
    end
get backward lines from file#pos
 #pos value should be at SOL (Start Of Line)

 args
   size ... indication of reading bytesize

 returner
   String object as lines