How to read last n messages?

[copark86]

While it might be easy, I really can't find it anywhere.

I have a c++ back-end program that logs everything with spdlog. I would like to send the last 5 messages to the front-end. How do I read last n messages from spdlog?

[tt4g]

You can use spdlog::sinks::ringbuffer_sink.

[copark86]

You can use spdlog::sinks::ringbuffer_sink.

Thanks! This is what I was looking for!

Just one more question. How should I use this? I tried the following but it didn't work.

spdlog::sinks::ringbuffer_sink_mt test(5); std::vector<std::string> last_log = test.last_formatted(5);
I am using spdlog in the following way.
spdlog::info("Downloading the serial number");

[tt4g]

Create spdlog::logger with spdlog::sinks::ringbuffer_sink and call spdlog::sinks::ringbuffer_sink::last_formatted(size_t) after logging.

Wiki (Creating loggers with multiple sinks): https://github.com/gabime/spdlog/wiki/2.-Creating-loggers#creating-loggers-with-multiple-sinks

Example:

auto ringbuffer_sink = std::make_shared<spdlog::sinks::ringbuffer_sink_mt>(5);

std::vector<spdlog::sink_ptr> sinks;
sinks.push_back(std::make_shared<spdlog::sinks::basic_file_sink_mt>("path/to/file.log"));
sinks.push_back(ringbuffer_sink);

auto logger = std::make_shared<spdlog::logger>("my_logger", sinks.begin(), sinks.end());

logger->info("foo");
logger->info("bar");
logger->info("baz");

// `log_message` contains "foo", "bar" and "baz".
std::vector<std::string> log_message = ringbuffer_sink->last_formatted();

[copark86]

with multiple sinks): https://github.com/gabime/spdlog/wiki/2.-Creating-loggers#creating-loggers-with-multiple-sinks

Example:

Thanks for the kind explanation. It would be very nice to include your example somewhere.

[tt4g]

Added ringbuffer_sink section in Wiki: https://github.com/gabime/spdlog/wiki/4.-Sinks