argument of daily_file_sink

[330305020]

For daily_file_sink , it mentioned that
/*

• Rotating file sink based on date.
• If truncate != false , the created file will be truncated.
• If max_files > 0, retain only the last max_files and delete previous.
  */
  I have two questions:

1. if truncate is set to true, based on which criteria the created file will be truncated? file size?
2. max_files: if one day the process is stopped, file of that day is not created, that means one file is missing, then files before process stop will not be deleted.
   

[tt4g]

1. if truncate is set to true, based on which criteria the created file will be truncated? file size?

This is the same behavior as if the O_TRUNC flag were specified for open() for log files.

spdlog/include/spdlog/details/file_helper-inl.h

Lines 32 to 60 in 2ee8bac

	SPDLOG_INLINE void file_helper::open(const filename_t &fname, bool truncate)
	{
	close();
	filename_ = fname;
	auto *mode = SPDLOG_FILENAME_T("ab");
	auto *trunc_mode = SPDLOG_FILENAME_T("wb");
	if (event_handlers_.before_open)
	{
	event_handlers_.before_open(filename_);
	}
	for (int tries = 0; tries < open_tries_; ++tries)
	{
	// create containing folder if not exists already.
	os::create_dir(os::dir_name(fname));
	if (truncate)
	{
	// Truncate by opening-and-closing a tmp file in "wb" mode, always
	// opening the actual log-we-write-to in "ab" mode, since that
	// interacts more politely with eternal processes that might
	// rotate/truncate the file underneath us.
	std::FILE *tmp;
	if (os::fopen_s(&tmp, fname, trunc_mode))
	{
	continue;
	}
	std::fclose(tmp);
	}

2. max_files: if one day the process is stopped, file of that day is not created, that means one file is missing, then files before process stop will not be deleted.

This is a specification.

You are only considering a pattern where there are no logfiles for one day old, but what do you think would happen if there were only 10 logfiles when max_file = 20?
Since no file older than 11 days exists, path_exists?(filename) will always return false, resulting in an infinite loop.