file/edit.go
func NewEdit(filename string) (*edit, error) {
	if err := Backup(filename); err != nil {
		return nil, err
	}

	file, err := os.OpenFile(filename, os.O_RDWR, 0666)
	if err != nil {
		return nil, err
	}

	return &edit{
		_editDefault,
		file,
		bufio.NewReadWriter(bufio.NewReader(file), bufio.NewWriter(file)),
	}, nil
}
func NewEdit(filename string) (*edit, error) {
	if err := Backup(filename); err != nil {
		return nil, err
	}

	file, err := os.OpenFile(filename, os.O_RDWR, 0666)
	if err != nil {
		return nil, err
	}

	return &edit{
		_editDefault,
		file,
		bufio.NewReadWriter(bufio.NewReader(file), bufio.NewWriter(file)),
	}, nil
}
// NewEdit opens a file to edit; it is created a backup.