spdlog

Sat, 21 Jun 2025 15:28:00 +0800

gabime/spdlog

spdlog

Very fast, header only, C++ logging library.

Install

Just copy the headers:

Copy the source folder to your build tree and use a C++11 compiler.

Or use your favorite package manager:

Ubuntu: apt-get install libspdlog-dev
Homebrew: brew install spdlog
FreeBSD: cd /usr/ports/devel/spdlog/ && make install clean
Fedora: yum install spdlog
Gentoo: emerge dev-libs/spdlog
Arch Linux: yaourt -S spdlog-git
vcpkg: vcpkg install spdlog

Platforms

Linux, FreeBSD, Solaris, AIX
Windows (vc 2013+, cygwin)
Mac OSX (clang 3.5+)
Android

Features

Very fast - performance is the primary goal (see benchmarks below).
Headers only, just copy and use.
Feature rich call style using the excellent fmt library.
Optional printf syntax support.
Asynchronous mode (optional)
Custom formatting.
Conditional Logging
Multi/Single threaded loggers.
Various log targets:
- Rotating log files.
- Daily log files.
- Console logging (colors supported).
- syslog.
- Windows debugger (OutputDebugString(..))
- Easily extendable with custom log targets (just implement a single function in the sink interface).
Severity based filtering - threshold levels can be modified in runtime as well as in compile time.

Benchmarks

Below are some benchmarks comparing popular log libraries under Ubuntu 64 bit, Intel i7-4770 CPU @ 3.40GHz

Synchronous mode

Time needed to log 1,000,000 lines in synchronous mode (in seconds, the best of 3 runs):

threads	boost log 1.54	glog	easylogging	spdlog
1	4.169s	1.066s	0.975s	0.392s
10	6.180s	3.032s	2.857s	0.773s
100	5.981s	1.139s	4.512s	0.587s

Asynchronous mode

Time needed to log 1,000,000 lines in asynchronous mode, i.e. the time it takes to put them in the async queue (in seconds, the best of 3 runs):

threads	g2log ^{async logger}	spdlog ^{async mode}
1	1.850s	0.39s
10	0.943s	0.416s
100	0.959s	0.413s

Usage Example


#include "spdlog/spdlog.h"

#include <iostream>
#include <memory>

void async_example();
void syslog_example();
void user_defined_example();
void err_handler_example();

namespace spd = spdlog;
int main(int, char*[])
{
    try
    {
        // Console logger with color
        auto console = spd::stdout_color_mt("console");
        console->info("Welcome to spdlog!");
        console->error("Some error message with arg{}..", 1);
	
        // Formatting examples
        console->warn("Easy padding in numbers like {:08d}", 12);
        console->critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
        console->info("Support for floats {:03.2f}", 1.23456);
        console->info("Positional args are {1} {0}..", "too", "supported");
        console->info("{:<30}", "left aligned");
	
	// Use global registry to retrieve loggers
        spd::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name) function");
        
        // Create basic file logger (not rotated)
        auto my_logger = spd::basic_logger_mt("basic_logger", "logs/basic.txt");
        my_logger->info("Some log message");

        // Create a file rotating logger with 5mb size max and 3 rotated files
        auto rotating_logger = spd::rotating_logger_mt("some_logger_name", "logs/mylogfile.txt", 1048576 * 5, 3);
        for (int i = 0; i < 10; ++i)
            rotating_logger->info("{} * {} equals {:>10}", i, i, i*i);

        // Create a daily logger - a new file is created every day on 2:30am
        auto daily_logger = spd::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);
        // trigger flush if the log severity is error or higher
        daily_logger->flush_on(spd::level::err);
        daily_logger->info(123.44);

        // Customize msg format for all messages
        spd::set_pattern("[%^+++%$] [%H:%M:%S %z] [thread %t] %v");
        console->info("This an info message with custom format (and custom color range between the '%^' and '%$')");
	console->error("This an error message with custom format (and custom color range between the '%^' and '%$')");

        // Runtime log levels
	spd::set_level(spd::level::info); //Set global log level to info
	console->debug("This message should not be displayed!");
	console->set_level(spd::level::debug); // Set specific logger's log level
	console->debug("This message should be displayed..");

        // Compile time log levels
        // define SPDLOG_DEBUG_ON or SPDLOG_TRACE_ON
        SPDLOG_TRACE(console, "Enabled only #ifdef SPDLOG_TRACE_ON..{} ,{}", 1, 3.23);
        SPDLOG_DEBUG(console, "Enabled only #ifdef SPDLOG_DEBUG_ON.. {} ,{}", 1, 3.23);

        // Asynchronous logging is very fast..
        // Just call spdlog::set_async_mode(q_size) and all created loggers from now on will be asynchronous..
        async_example();

        // syslog example. linux/osx only
        syslog_example();

        // android example. compile with NDK
        android_example();

        // Log user-defined types example
        user_defined_example();

        // Change default log error handler
        err_handler_example();

        // Apply a function on all registered loggers
        spd::apply_all([&](std::shared_ptr<spd::logger> l)
        {
            l->info("End of example.");
        });

        // Release and close all loggers
        spd::drop_all();
    }
    // Exceptions will only be thrown upon failed logger or sink construction (not during logging)
    catch (const spd::spdlog_ex& ex)
    {
        std::cout << "Log init failed: " << ex.what() << std::endl;
        return 1;
    }
}

void async_example()
{
    size_t q_size = 4096; 
    spd::set_async_mode(q_size);
    auto async_file = spd::daily_logger_st("async_file_logger", "logs/async_log.txt");
    for (int i = 0; i < 100; ++i)
        async_file->info("Async message #{}", i);
}

//syslog example
void syslog_example()
{
#ifdef SPDLOG_ENABLE_SYSLOG 
    std::string ident = "spdlog-example";
    auto syslog_logger = spd::syslog_logger("syslog", ident, LOG_PID);
    syslog_logger->warn("This is warning that will end up in syslog..");
#endif
}

// user defined types logging by implementing operator<<
struct my_type
{
    int i;
    template<typename OStream>
    friend OStream& operator<<(OStream& os, const my_type &c)
    {
        return os << "[my_type i="<<c.i << "]";
    }
};

#include <spdlog/fmt/ostr.h> // must be included
void user_defined_example()
{
    spd::get("console")->info("user defined type: {}", my_type { 14 });
}

//
//custom error handler
//
void err_handler_example()
{	
	spd::set_error_handler([](const std::string& msg) {
		std::cerr << "my err handler: " << msg << std::endl;
	}); 
	// (or logger->set_error_handler(..) to set for specific logger)
}

Documentation

Documentation can be found in the wiki pages.

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spdlog

gabime/spdlog

spdlog

Install

Just copy the headers:

Or use your favorite package manager:

Platforms

Features

Benchmarks

Synchronous mode

Asynchronous mode

Usage Example

Documentation