def exiftool_args
      fail MultiExiftool::Error, 'No filenames.' if filenames.empty?
      cmd = []
      cmd << Writer.mandatory_args
      cmd << options_args
      cmd << values_args
      cmd << filenames
      cmd.flatten
    end
def exiftool_args
      fail MultiExiftool::Error, 'No filenames.' if filenames.empty?
      cmd = []
      cmd << Writer.mandatory_args
      cmd << options_args
      cmd << values_args
      cmd << filenames
      cmd.flatten
    end
Getting the command-line arguments which would be executed
 when calling #write. It could be useful for logging, debugging or
 maybe even for creating a batch-file with exiftool command to be
 processed.