How to write a log file in text mode (rather than in binary mode)?

[N-Dekker]

When a file is specified as sink, it appears to be opened in binary mode: the letter b in both "ab" and "wb", at

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

Lines 37 to 38 in 927cc29

	auto *mode = SPDLOG_FILENAME_T("ab");
	auto *trunc_mode = SPDLOG_FILENAME_T("wb");

As a consequence, a \n with a string passed to the logger won't be converted automatically to \r\n, even though this might be preferable on Windows. For example:

auto text_file_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("my-log.txt");
text_file_sink->set_pattern("%v");
spdlog::default_logger()->sinks().push_back(text_file_sink);
spdlog::info("Line one\nLine two");

The resulting text file ("my-log.txt") looks as follows:

Line one\n
Line two\r\n

Is it be possible to tweak spdlog to write a log file in text mode, so that on Windows, each \n would be translated automatically to \r\n?

[tt4g]

spdlog does not provide an option to change the file open mode.
You can open pull requests if you need such a feature.

It should be possible to add something like an SPDLOG_EOL macro that changes the newline character that spdlog adds to the end of a line.

spdlog/include/spdlog/tweakme.h

Lines 62 to 66 in 927cc29

	///////////////////////////////////////////////////////////////////////////////
	// Uncomment to override default eol ("\n" or "\r\n" under Linux/Windows)
	//
	// #define SPDLOG_EOL ";-)\n"
	///////////////////////////////////////////////////////////////////////////////

spdlog/include/spdlog/details/os.h

Lines 23 to 32 in 654dbc5

	// eol definition
	#if !defined(SPDLOG_EOL)
	# ifdef _WIN32
	# define SPDLOG_EOL "\r\n"
	# else
	# define SPDLOG_EOL "\n"
	# endif
	#endif
	SPDLOG_CONSTEXPR static const char *default_eol = SPDLOG_EOL;

A workaround available in spdlog v1.11.0 is to create a custom formatter.
Wiki: https://github.com/gabime/spdlog/wiki/3.-Custom-formatting#extending-spdlog-with-your-own-flags

It should be possible to implement this with reference to v_formatter which handles the %v flag.
Just output an additional \r when \n appears in msg.paylod.

spdlog/include/spdlog/pattern_formatter-inl.h

Lines 679 to 692 in 927cc29

	template<typename ScopedPadder>
	class v_formatter final : public flag_formatter
	{
	public:
	explicit v_formatter(padding_info padinfo)
	: flag_formatter(padinfo)
	{}
	void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
	{
	ScopedPadder p(msg.payload.size(), padinfo_, dest);
	fmt_helper::append_string_view(msg.payload, dest);
	}
	};

[N-Dekker]

Thanks @tt4g I'm preparing a pull request: https://github.com/N-Dekker/spdlog/tree/file_sink-text-mode (still under construction)

Update: the pull request is there, please check: #2636