Could I creating multiple file loggers with the difference output format with the same output file

[NiceBlueChai]

Could I creating multiple file loggers with the difference output format with the same output file

[tt4g]

You can do it, just pass a sink that makes the same file the output destination to one logger: https://github.com/gabime/spdlog/wiki/2.-Creating-loggers#creating-loggers-with-multiple-sinks

Note, file_sink does not lock files on write, so log messages may be mixed if log output from multiple threads.

Note also that logger->set_pattern() calls the same named method of all sinks in the logger, so sink->set_pattern() must be called for each.

auto first_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("log.txt");
auto second_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("log.txt");

first_sink->set_pattern(...);
second_sink->set_pattern(...);

std::vector<spdlog::sink_ptr> sinks;
sinks.push_back(first_sink);
sinks.push_back(second_sink);
auto logger = std::make_shared<spdlog::logger>("name", std::begin(sinks), std::end(sinks));

// Don't call it
logger->set_pattern(...);

//register it if you need to access it globally
spdlog::register_logger(logger);