log库spdlog简介及使用[通俗易懂]

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spdlog 是一个开源的、快速的、仅有头文件的 C++11 日志库，代码地址在 https://www.php.cn/link/037be3f3bf37ffed5e5b8750c514ad17 ，目前最新发布版本为 0.14.0。它提供了向流、标准输出、文件、系统日志、调试器等多种目标输出日志的能力，支持的平台包括 Windows、Linux、Mac、Android。

spdlog 的特性包括：

(1) 速度极快，性能是其主要目标；

(2) 仅包含头文件，方便使用；

(3) 日志格式化处理使用开源的 fmt 库（https://www.php.cn/link/02251d47085ed33996c248c852dd3fa3）；

(4) 可选地支持 printf 语法；

(5) 提供非常快的异步模式（可选），支持异步写日志；

(6) 支持自定义格式；

(7) 支持条件日志；

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(8) 支持多线程和单线程日志；

(9) 多种日志目标：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 调试器；易于扩展自定义日志目标；

(10) 支持日志输出级别：阈值级别可以在运行时或编译时修改。

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 color
        auto console = spd::stdout_color_mt("console");
        console->info("Welcome to spdlog!");
        console->error("Some error message with arg{}..", 1);
        // Conditional logging example
        console->info_if(true, "Welcome to spdlog conditional logging!");
        // 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("{");
        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 files
        auto 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 2:30am
        auto 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 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 ***");
        rotating_logger->info("This is another message with custom format");
        // Runtime log levels
        spd::set_level(spd::level::info); //Set global log level to info
        console->debug("This message shold not be displayed!");
        console->set_level(spd::level::debug); // Set specific logger's log level
        console->debug("This message shold 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);
        SPDLOG_DEBUG_IF(console, true, "This is a debug log");
        // Apply a function on all registered loggers
        spd::apply_all([&](std::shared_ptr<spdlog::logger> l) { l->info("End of example."); });
        // Release and close all loggers
        spdlog::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 initialization failed: " << ex.what() << std::endl;
    }
    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_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
    return 0;
}
// user defined types logging by implementing operator<<
struct my_type {
    int i;
    explicit my_type(int a):i(a){}
};
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 {
        auto console = spd::stdout_color_mt("console");
        console->info("user defined type: {}", my_type{ 14 });
    } catch (const spd::spdlog_ex& ex) {
        std::cout << "Log initialization failed: " << ex.what() << std::endl;
    }
    return 0;
}
// error handling (can be set globally or per logger(using spdlog::logger::set_error_handler(..))
spdlog::set_error_handler([](const std::string& msg){std::cerr << "*** spdlog error: " << msg << " ***" << std::endl;});
int test_spdlog_error_handling(){
    try {
        auto console = spd::stdout_color_mt("console");
        console->info("some invalid message to trigger an error {}{}{}{}", 3);
    } catch (const spd::spdlog_ex& ex) {
        std::cout << "Log initialization failed: " << ex.what() << std::endl;
    }
    return 0;
}

执行结果如下：

GitHub： https://www.php.cn/link/df236b5b4ec12e88f2cb714b641b8cc4

发布者：全栈程序员栈长，转载请注明出处：https://www.php.cn/link/06ac68cc0db1c6c3992eb55812168e55

原文链接：https://www.php.cn/link/c8377ad2a50fb65de28b11cfc628d75c