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# spdlog
Very fast, header-only/compiled, C++ logging library. [](https://github.com/gabime/spdlog/actions/workflows/ci.yml) [](https://ci.appveyor.com/project/gabime/spdlog) [](https://github.com/gabime/spdlog/releases/latest)
## Install
#### Header only version
Copy the include [folder](https://github.com/gabime/spdlog/tree/v1.x/include/spdlog) to your build tree and use a C++11 compiler.
#### Compiled version (recommended - much faster compile times)
```console$ git clone https://github.com/gabime/spdlog.git$ cd spdlog && mkdir build && cd build$ cmake .. && make -j``` see example [CMakeLists.txt](https://github.com/gabime/spdlog/blob/v1.x/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`* vcpkg: `vcpkg install spdlog`* conan: `spdlog/[>=1.4.1]`* conda: `conda install -c conda-forge spdlog`* build2: ```depends: spdlog ^1.8.2```
## Features
* Very fast (see [benchmarks](#benchmarks) below).* Headers only or compiled* Feature rich formatting, using the excellent [fmt](https://github.com/fmtlib/fmt) library.* Asynchronous mode (optional)* [Custom](https://github.com/gabime/spdlog/wiki/3.-Custom-formatting) 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(..)```). * Easily [extendable](https://github.com/gabime/spdlog/wiki/4.-Sinks#implementing-your-own-sink) with custom log targets.* Log filtering - log levels can be modified in runtime as well as in compile time.* Support for loading log levels from argv or from environment var.* [Backtrace](#backtrace-support) support - store debug messages in a ring buffer and display later on demand. ## Usage samples
#### Basic usage
```c++#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 // define SPDLOG_ACTIVE_LEVEL to desired level SPDLOG_TRACE("Some trace message with param {}", 42); SPDLOG_DEBUG("Some debug message");}
```---#### Create stdout/stderr logger object
```c++#include "spdlog/spdlog.h"
#include "spdlog/sinks/stdout_color_sinks.h"
void stdout_example(){ // create 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
```c++#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
```c++#include "spdlog/sinks/rotating_file_sink.h"
void rotating_example(){ // Create a file rotating logger with 5mb 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
```c++
#include "spdlog/sinks/daily_file_sink.h"
void daily_example(){ // Create a daily logger - a new file is created every day on 2:30am auto logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);}
```
---#### Backtrace support
```c++// Debug messages can be stored in a ring buffer instead of being logged immediately.// This is useful in order to display debug logs only when really needed (e.g. when error happens).// When needed, call dump_backtrace() to see them.
spdlog::enable_backtrace(32); // Store the latest 32 messages in a buffer. Older messages will be dropped.// 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
```c++// 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
```c++// 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
```c++// 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 to 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 different format and log level
```c++
// create 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");}```
---#### Asynchronous logging
```c++#include "spdlog/async.h"
#include "spdlog/sinks/basic_file_sink.h"
void async_example(){ // default thread pool settings can be modified *before* creating the async logger: // spdlog::init_thread_pool(8192, 1); // queue with 8k items and 1 backing thread. auto async_file = spdlog::basic_logger_mt<spdlog::async_factory>("async_file_logger", "logs/async_log.txt"); // alternatively: // auto async_file = spdlog::create_async<spdlog::sinks::basic_file_sink_mt>("async_file_logger", "logs/async_log.txt"); }
```
---#### Asynchronous logger with multi sinks
```c++#include "spdlog/sinks/stdout_color_sinks.h"
#include "spdlog/sinks/rotating_file_sink.h"
void multi_sink_example2(){ spdlog::init_thread_pool(8192, 1); auto stdout_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt >(); auto rotating_sink = std::make_shared<spdlog::sinks::rotating_file_sink_mt>("mylog.txt", 1024*1024*10, 3); std::vector<spdlog::sink_ptr> sinks {stdout_sink, rotating_sink}; auto logger = std::make_shared<spdlog::async_logger>("loggername", sinks.begin(), sinks.end(), spdlog::thread_pool(), spdlog::async_overflow_policy::block); spdlog::register_logger(logger);}``` ---#### User defined types
```c++template<>struct fmt::formatter<my_type> : fmt::formatter<std::string>{ auto format(my_type my, format_context &ctx) -> decltype(ctx.out()) { return format_to(ctx.out(), "[my_type i={}]", my.i); }};
void user_defined_example(){ spdlog::info("user defined type: {}", my_type(14));}
```
---#### User defined flags in the log pattern
```c++ // Log patterns can contain custom flags.// the following example will add new flag '%*' - which will be bound to a <my_formatter_flag> instance.#include "spdlog/pattern_formatter.h"
class my_formatter_flag : public spdlog::custom_flag_formatter{public: void format(const spdlog::details::log_msg &, const std::tm &, spdlog::memory_buf_t &dest) override { std::string some_txt = "custom-flag"; dest.append(some_txt.data(), some_txt.data() + some_txt.size()); }
std::unique_ptr<custom_flag_formatter> clone() const override { return spdlog::details::make_unique<my_formatter_flag>(); }};
void custom_flags_example(){ auto formatter = std::make_unique<spdlog::pattern_formatter>(); formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v"); spdlog::set_formatter(std::move(formatter));}
```
---#### Custom error handler
```c++void err_handler_example(){ // can be set globally or per logger(logger->set_error_handler(..)) spdlog::set_error_handler([](const std::string &msg) { spdlog::get("console")->error("*** LOGGER ERROR ***: {}", msg); }); spdlog::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3);}
```
---#### syslog
```c++#include "spdlog/sinks/syslog_sink.h"
void syslog_example(){ std::string ident = "spdlog-example"; auto syslog_logger = spdlog::syslog_logger_mt("syslog", ident, LOG_PID); syslog_logger->warn("This is warning that will end up in syslog.");}```---#### Android example
```c++#include "spdlog/sinks/android_sink.h"
void android_example(){ std::string tag = "spdlog-android"; auto android_logger = spdlog::android_logger_mt("android", tag); android_logger->critical("Use \"adb shell logcat\" to view this message.");}```
---#### Load log levels from env variable or from argv
```c++#include "spdlog/cfg/env.h"
int main (int argc, char *argv[]){ spdlog::cfg::load_env_levels(); // or from command line: // ./example SPDLOG_LEVEL=info,mylogger=trace // #include "spdlog/cfg/argv.h" // for loading levels from argv // spdlog::cfg::load_argv_levels(argc, argv);}```So then you can:
```console$ export SPDLOG_LEVEL=info,mylogger=trace$ ./example```
---#### Log file open/close event handlers
```c++// You can get callbacks from spdlog before/after log file has been opened or closed. // This is useful for cleanup procedures or for adding someting the start/end of the log files.void file_events_example(){ // pass the spdlog::file_event_handlers to file sinks for open/close log file notifications spdlog::file_event_handlers handlers; handlers.before_open = [](spdlog::filename_t filename) { spdlog::info("Before opening {}", filename); }; handlers.after_open = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("After opening\n", fstream); }; handlers.before_close = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("Before closing\n", fstream); }; handlers.after_close = [](spdlog::filename_t filename) { spdlog::info("After closing {}", filename); }; auto my_logger = spdlog::basic_logger_st("some_logger", "logs/events-sample.txt", true, handlers); }```
---#### Replace the Default Logger
```c++void replace_default_logger_example(){ auto new_logger = spdlog::basic_logger_mt("new_default_logger", "logs/new-default-log.txt", true); spdlog::set_default_logger(new_logger); spdlog::info("new logger log message");}```
---## Benchmarks
Below are some [benchmarks](https://github.com/gabime/spdlog/blob/v1.x/bench/bench.cpp) done in Ubuntu 64 bit, Intel i7-4770 CPU @ 3.40GHz
#### Synchronous mode
```[info] **************************************************************[info] Single thread, 1,000,000 iterations[info] **************************************************************[info] basic_st Elapsed: 0.17 secs 5,777,626/sec[info] rotating_st Elapsed: 0.18 secs 5,475,894/sec[info] daily_st Elapsed: 0.20 secs 5,062,659/sec[info] empty_logger Elapsed: 0.07 secs 14,127,300/sec[info] **************************************************************[info] C-string (400 bytes). Single thread, 1,000,000 iterations[info] **************************************************************[info] basic_st Elapsed: 0.41 secs 2,412,483/sec[info] rotating_st Elapsed: 0.72 secs 1,389,196/sec[info] daily_st Elapsed: 0.42 secs 2,393,298/sec[info] null_st Elapsed: 0.04 secs 27,446,957/sec[info] **************************************************************[info] 10 threads, competing over the same logger object, 1,000,000 iterations[info] **************************************************************[info] basic_mt Elapsed: 0.60 secs 1,659,613/sec[info] rotating_mt Elapsed: 0.62 secs 1,612,493/sec[info] daily_mt Elapsed: 0.61 secs 1,638,305/sec[info] null_mt Elapsed: 0.16 secs 6,272,758/sec```#### Asynchronous mode
```[info] -------------------------------------------------[info] Messages : 1,000,000[info] Threads : 10[info] Queue : 8,192 slots[info] Queue memory : 8,192 x 272 = 2,176 KB [info] -------------------------------------------------[info] [info] *********************************[info] Queue Overflow Policy: block[info] *********************************[info] Elapsed: 1.70784 secs 585,535/sec[info] Elapsed: 1.69805 secs 588,910/sec[info] Elapsed: 1.7026 secs 587,337/sec[info] [info] *********************************[info] Queue Overflow Policy: overrun[info] *********************************[info] Elapsed: 0.372816 secs 2,682,285/sec[info] Elapsed: 0.379758 secs 2,633,255/sec[info] Elapsed: 0.373532 secs 2,677,147/sec
```
## Documentation
Documentation can be found in the [wiki](https://github.com/gabime/spdlog/wiki/1.-QuickStart) pages.
---
Thanks to [JetBrains](https://www.jetbrains.com/?from=spdlog) for donating product licenses to help develop **spdlog** <a href="https://www.jetbrains.com/?from=spdlog"><img src="logos/jetbrains-variant-4.svg" width="94" align="center" /></a>
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