spdlog

     

Fast C++ logging library

Install

Header-only version

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

Compiled version (recommended - much faster compile times)

$ git clone https://github.com/gabime/spdlog.git
$ cd spdlog && mkdir build && cd build
$ cmake .. && cmake --build .

see example CMakeLists.txt on how to use.

Platforms

• Linux, FreeBSD, OpenBSD, Solaris, AIX
• Windows (msvc 2013+, cygwin)
• macOS (clang 3.5+)
• Android

Package managers:

• Debian: sudo apt install libspdlog-dev
• Homebrew: brew install spdlog
• MacPorts: sudo port install spdlog
• FreeBSD: pkg install spdlog
• Fedora: dnf install spdlog
• Gentoo: emerge dev-libs/spdlog
• Arch Linux: pacman -S spdlog
• openSUSE: sudo zypper in spdlog-devel
• ALT Linux: apt-get install libspdlog-devel
• vcpkg: vcpkg install spdlog
• conan: conan install --requires=spdlog/[*]
• conda: conda install -c conda-forge spdlog
• build2: depends: spdlog ^1.8.2

Features

• Very fast (see benchmarks below).
• Headers only or compiled
• Feature-rich formatting, using the excellent fmt library.
• Asynchronous mode (optional)
• Custom formatting.
• Multi/Single threaded loggers.
• Various log targets:
  • Rotating log files.
  • Daily log files.
  • Console logging (colors supported).
  • syslog.
  • Windows event log.
  • Windows debugger (OutputDebugString(..)).
  • Log to Qt widgets (example).
  • Easily extendable with custom log targets.
• Log filtering - log levels can be modified at runtime as well as compile time.
• Support for loading log levels from argv or environment var.
• Backtrace support - store debug messages in a ring buffer and display them later on demand.

Usage samples

Basic usage

#include "spdlog/spdlog.h"

int main() 
{
    spdlog::info("Welcome to spdlog!");
    spdlog::error("Some error message with arg: {}", 1);
    
    spdlog::warn("Easy padding in numbers like {:08d}", 12);
    spdlog::critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
    spdlog::info("Support for floats {:03.2f}", 1.23456);
    spdlog::info("Positional args are {1} {0}..", "too", "supported");
    spdlog::info("{:<30}", "left aligned");
    
    spdlog::set_level(spdlog::level::debug); // Set *global* log level to debug
    spdlog::debug("This message should be displayed..");    
    
    // change log pattern
    spdlog::set_pattern("[%H:%M:%S %z] [%n] [%^---%L---%$] [thread %t] %v");
    
    // Compile time log levels
    // Note that this does not change the current log level, it will only
    // remove (depending on SPDLOG_ACTIVE_LEVEL) the call on the release code.
    SPDLOG_TRACE("Some trace message with param {}", 42);
    SPDLOG_DEBUG("Some debug message");
}

---

Create stdout/stderr logger object

#include "spdlog/spdlog.h"
#include "spdlog/sinks/stdout_color_sinks.h"
void stdout_example()
{
    // create a color multi-threaded logger
    auto console = spdlog::stdout_color_mt("console");    
    auto err_logger = spdlog::stderr_color_mt("stderr");    
    spdlog::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name)");
}

---

Basic file logger

#include "spdlog/sinks/basic_file_sink.h"
void basic_logfile_example()
{
    try 
    {
        auto logger = spdlog::basic_logger_mt("basic_logger", "logs/basic-log.txt");
    }
    catch (const spdlog::spdlog_ex &ex)
    {
        std::cout << "Log init failed: " << ex.what() << std::endl;
    }
}

---

Rotating files

#include "spdlog/sinks/rotating_file_sink.h"
void rotating_example()
{
    // Create a file rotating logger with 5 MB size max and 3 rotated files
    auto max_size = 1048576 * 5;
    auto max_files = 3;
    auto logger = spdlog::rotating_logger_mt("some_logger_name", "logs/rotating.txt", max_size, max_files);
}

---

Daily files

#include "spdlog/sinks/daily_file_sink.h"
void daily_example()
{
    // Create a daily logger - a new file is created every day at 2:30 am
    auto logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);
}

---

Backtrace support

// Debug messages can be stored in a ring buffer instead of being logged immediately.
// This is useful to display debug logs only when needed (e.g. when an error happens).
// When needed, call dump_backtrace() to dump them to your log.

spdlog::enable_backtrace(32); // Store the latest 32 messages in a buffer. 
// or my_logger->enable_backtrace(32)..
for(int i = 0; i < 100; i++)
{
  spdlog::debug("Backtrace message {}", i); // not logged yet..
}
// e.g. if some error happened:
spdlog::dump_backtrace(); // log them now! show the last 32 messages
// or my_logger->dump_backtrace(32)..

---

Periodic flush

// periodically flush all *registered* loggers every 3 seconds:
// warning: only use if all your loggers are thread-safe ("_mt" loggers)
spdlog::flush_every(std::chrono::seconds(3));

---

Stopwatch

// Stopwatch support for spdlog
#include "spdlog/stopwatch.h"
void stopwatch_example()
{
    spdlog::stopwatch sw;    
    spdlog::debug("Elapsed {}", sw);
    spdlog::debug("Elapsed {:.3}", sw);       
}

---

Log binary data in hex

// many types of std::container<char> types can be used.
// ranges are supported too.
// format flags:
// {:X} - print in uppercase.
// {:s} - don't separate each byte with space.
// {:p} - don't print the position on each line start.
// {:n} - don't split the output into lines.
// {:a} - show ASCII if :n is not set.

#include "spdlog/fmt/bin_to_hex.h"

void binary_example()
{
    auto console = spdlog::get("console");
    std::array<char, 80> buf;
    console->info("Binary example: {}", spdlog::to_hex(buf));
    console->info("Another binary example:{:n}", spdlog::to_hex(std::begin(buf), std::begin(buf) + 10));
    // more examples:
    // logger->info("uppercase: {:X}", spdlog::to_hex(buf));
    // logger->info("uppercase, no delimiters: {:Xs}", spdlog::to_hex(buf));
    // logger->info("uppercase, no delimiters, no position info: {:Xsp}", spdlog::to_hex(buf));
}

---

Logger with multi sinks - each with a different format and log level

// create a logger with 2 targets, with different log levels and formats.
// The console will show only warnings or errors, while the file will log all. 
void multi_sink_example()
{
    auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>();
    console_sink->set_level(spdlog::level::warn);
    console_sink->set_pattern("[multi_sink_example] [%^%l%$] %v");

    auto file_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("logs/multisink.txt", true);
    file_sink->set_level(spdlog::level::trace);

    spdlog::logger logger("multi_sink", {console_sink, file_sink});
    logger.set_level(spdlog::level::debug);
    logger.warn("this should appear in both console and file");
    logger.info("this message should not appear in the console, only in the file");
}

---

Register several loggers - change global level

// Creation of loggers. Set levels to all registered loggers. 
void set_level_example()
{
    auto logger1 = spdlog::basic_logger_mt("logger1", "logs/logger1.txt");
    auto logger2 = spdlog::basic_logger_mt("logger2", "logs/logger2.txt");

    spdlog::set_default_logger(logger2);
    spdlog::default_logger()->set_level(spdlog::level::trace); // set level for the default logger (logger2) to trace

    spdlog::trace("trace message to the logger2 (specified as default)");

    spdlog::set_level(spdlog::level::off) // (sic!) set level for *all* registered loggers to off (disable)
  
    logger1.warn("warn message will not appear because the level set to off");
    logger2.warn("warn message will not appear because the level set to off");
    spdlog::warn("warn message will not appear because the level set to off");
}

---

User-defined callbacks about log events

// create a logger with a lambda function callback, the callback will be called
// each time something is logged to the logger
void callback_example()
{
    auto callback_sink = std::make_shared<spdlog::sinks::callback_sink_mt>([](const spdlog::details::log_msg &msg) {
         // for example you can be notified by sending an email to yourself
    });
    callback_sink->set_level(spdlog::level::err);

    auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>();
    spdlog::logger logger("custom_callback_logger", {console_sink, callback_sink});

    logger.info("some info log");
    logger.error("critical issue"); // will notify you
}