log库spdlog简介及使用

spdlog是一个开源的、快速的、仅有头文件的C++11 日志库，code地址在 https://github.com/gabime/spdlog ，目前最新的发布版本为0.14.0。它提供了向流、标准输出、文件、系统日志、调试器等目标输出日志的能力。它支持的平台包括Windows、Linux、Mac、Android。

spdlog特性：

(1)、非常快，性能是它的主要目标；

(2)、仅包括头文件；

(3)、日志的格式化处理使用开源的fmt库(  https://github.com/fmtlib/fmt )；

(4)、可选的printf语法支持；

(5)、非常快的异步模式(可选)，支持异步写日志；

(6)、自定义格式；

(7)、条件日志；

(8)、多线程/单线程日志；

(9)、各种日志目标：可对日志文件进行循环输出；可每日生成日志文件；支持控制台日志输出(支持颜色)；系统日志；Windows debugger；较容易扩展自定义日志目标；

(10)、支持日志输出级别：阈值级别既可以在运行时也可以在编译时修改。

以下是测试代码，主要来自spdlog/example/example.cpp:

#include "funset.hpp"#include <iostream>#include "spdlog/spdlog.h"#include "spdlog/fmt/ostr.h"namespace spd = spdlog;int test_spdlog_console(){try {// Console logger with colorauto console = spd::stdout_color_mt("console");console->info("Welcome to spdlog!");console->error("Some error message with arg{}..", 1);// Conditional logging exampleconsole->info_if(true, "Welcome to spdlog conditional logging!");// Formatting examplesconsole->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");SPDLOG_DEBUG_IF(console, true, "This is a debug log");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", "E:/GitCode/Messy_Test/testdata/basic_log");my_logger->info("Some log message");// Create a file rotating logger with 5mb size max and 3 rotated filesauto rotating_logger = spd::rotating_logger_mt("some_logger_name", "E:/GitCode/Messy_Test/testdata/mylogfile_log", 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 2:30amauto daily_logger = spd::daily_logger_mt("daily_logger", "E:/GitCode/Messy_Test/testdata/daily_log", 2, 30);// trigger flush if the log severity is error or higherdaily_logger->flush_on(spd::level::err);daily_logger->info(123.44);// Customize msg format for all messagesspd::set_pattern("*** [%H:%M:%S %z] [thread %t] %v ***");rotating_logger->info("This is another message with custom format");// Runtime log levelsspd::set_level(spd::level::info); //Set global log level to infoconsole->debug("This message shold not be displayed!");console->set_level(spd::level::debug); // Set specific logger's log levelconsole->debug("This message shold be displayed..");// Compile time log levels// define SPDLOG_DEBUG_ON or SPDLOG_TRACE_ONSPDLOG_TRACE(console, "Enabled only #ifdef SPDLOG_TRACE_ON..{} ,{}", 1, 3.23);SPDLOG_DEBUG(console, "Enabled only #ifdef SPDLOG_DEBUG_ON.. {} ,{}", 1, 3.23);SPDLOG_DEBUG_IF(console, true, "This is a debug log");// Apply a function on all registered loggersspd::apply_all([&](std::shared_ptr<spdlog::logger> l) { l->info("End of example."); });// Release and close all loggersspdlog::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;}return 0;}int test_spdlog_async(){// Asynchronous logging is very fast..// Just call spdlog::set_async_mode(q_size) and all created loggers from now on will be asynchronous..size_t q_size = 4096; //queue size must be power of 2spdlog::set_async_mode(q_size);auto async_file = spd::daily_logger_st("async_file_logger", "E:/GitCode/Messy_Test/testdata/async_log");for (int i = 0; i < 100; ++i)async_file->info("Async message #{}", i);return 0;}int test_spdlog_syslog(){// there is no syslog.h file in windows, so macro SPDLOG_ENABLE_SYSLOG should be disenable#ifdef SPDLOG_ENABLE_SYSLOGstd::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.");#endifreturn 0;}// 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 << "]";}};int test_spdlog_user_defined(){try {//spd::get("console")->info("user defined type: {}", my_type{ 14 });auto console = spd::stdout_color_mt("console");console->info("user defined type: {}", my_type{ 14 });} catch (const spd::spdlog_ex& ex) {std::cout << "user defined log fail: " << ex.what() << std::endl;return -1;}return 0;}int test_spdlog_err_handler(){// can be set globaly or per logger(logger->set_error_handler(..))spdlog::set_error_handler([](const std::string& msg){std::cerr << "my err handler: " << msg << std::endl;});//spd::get("console")->info("some invalid message to trigger an error {}{}{}{}", 3);auto console = spd::stdout_color_mt("console");console->info("some invalid message to trigger an error {}{}{}{}", 3);return 0;}

执行结果如下：

GitHub： https://github.com/fengbingchun/Messy_Test