C++ spdlog日志管理

【1】spdlog简介

spdlog是一个开源的、快速的、仅有头文件的基于C++11实现的一款C++专用日志管理库。

【2】源码下载

下载地址：https://github.com/gabime/spdlog

【3】工程配置

（1）解压缩源码包

解压后，找到include文件夹。类比本地：

注意：include文件夹里是所需的头文件及源码。

（2）工程配置

2.1 新建一个C++控制台应用程序空项目spdlog

2.2 在项目属性页：VC++目录->包含目录 中添加上述include路径，如下图：

2.3 在项目中添加头文件即可，如下：

#include "spdlog/spdlog.h"
using namespace spdlog;

OK 请尽情享用。是的，没错，就是这么简单，你不用怀疑你自己。。。。

【4】应用示例

为了更权威、更有说服力，遂决定把源码包中的example示例贴出来（加了若干自己理解的信息）

应用示例如下：

//
// Copyright(c) 2015 Gabi Melman.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

// spdlog usage example

#include <cstdio>

// 标准输出类型
void stdout_logger_example();
// 基本类型：日志文件会一直被写入，不断变大。
void basic_example();
// 滚动类型：日志文件会先写入一个文件，当超出规定大小时，会备份(或删除)当前日志内容，重建文件开始写入。
/* 说明：从函数声明可以看出，参数max_file_size规定了文件数量的最大值，当文件数量超过此值就会把最早的先清空。
参数max_file_size规定了滚动文件的个数。当logger_name存满时，将其名称更改为logger_name.1，再新建一个logger_name文件来存储新的日志。
再次存满时，把logger_name.1改名为logger_name.2，logger_name改名为logger_name.1，再新建一个logger_name来存放新的日志。
以此类推，max_files 数量为几，就可以有几个logger_name文件用来滚动。
*/
void rotating_example();
// 每日类型：每天新建一个日志，新建日志文件时间可以自定义。
void daily_example();
// 异步模式类型
void async_example();
// 二进制类型
void binary_example();
// 追踪类型
void trace_example();
// 多汇入类型
/* 带多接收器的记录器 - 每个接收器都有不同的格式和日志级别
譬如，创建具有 2 个不同日志级别和格式的目标的记录器。
控制台将仅显示警告或错误，而文件将记录所有。
*/
void multi_sink_example();
// 自定义类型
void user_defined_example();
// 错误处理类型
/*
自定义错误处理程序。将在日志失败时触发。
可以全局设置或针对性设置
*/
void err_handler_example();
// 系统类型 (linux/osx/freebsd)
void syslog_example();

// 重点备注:
// 日志实时写入接口：logger->flush();
/*
上述各种日志文件，仅在程序退出时才保存日志。
如果要想在程序运行时也能够实时保存日志，可以在程序中添加如上语句。
具体参见譬如166行的应用示例
*/

#include "spdlog/spdlog.h"

int main(int, char* [])
{
    spdlog::info("Welcome to spdlog version {}.{}.{}  !", SPDLOG_VER_MAJOR, SPDLOG_VER_MINOR, SPDLOG_VER_PATCH);
    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("{:>8} aligned, {:<8} aligned", "right", "left");

    // Runtime log levels
    // 支持设置日志级别：低于设置级别的日志将不会被输出。各level排序详见源码，数值越大级别越高：
    /*
    enum level_enum
    {
        trace = SPDLOG_LEVEL_TRACE,
        debug = SPDLOG_LEVEL_DEBUG,
        info = SPDLOG_LEVEL_INFO,
        warn = SPDLOG_LEVEL_WARN,
        err = SPDLOG_LEVEL_ERROR,
        critical = SPDLOG_LEVEL_CRITICAL,
        off = SPDLOG_LEVEL_OFF,
    };
    */
    spdlog::set_level(spdlog::level::info); // Set global log level to info
    spdlog::debug("This message should not be displayed!");
    spdlog::set_level(spdlog::level::trace); // Set specific logger's log level
    spdlog::debug("This message should be displayed..");

    // Customize msg format for all loggers
    // 支持自定义日志格式
    spdlog::set_pattern("[%H:%M:%S %z] [%^%L%$] [thread %t] %v");
    spdlog::info("This an info message with custom format");
    spdlog::set_pattern("%+"); // back to default format
    spdlog::set_level(spdlog::level::info);

    // 支持回溯分析
    // Backtrace support
    // Loggers can store in a ring buffer all messages (including debug/trace) for later inspection.
    // When needed, call dump_backtrace() to see what happened:
    spdlog::enable_backtrace(10); // create ring buffer with capacity of 10  messages
    for (int i = 0; i < 100; i++)
    {
        spdlog::debug("Backtrace message {}", i); // not logged.
    }
    // e.g. if some error happened:
    spdlog::dump_backtrace(); // log them now!

    try
    {
        stdout_logger_example();
        basic_example();
        rotating_example();
        daily_example();
        async_example();
        binary_example();
        multi_sink_example();
        user_defined_example();
        err_handler_example();
        trace_example();

        // Flush all *registered* loggers using a worker thread every 3 seconds.
        // note: registered loggers *must* be thread safe for this to work correctly!
        spdlog::flush_every(std::chrono::seconds(3));

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

        // Release all spdlog resources, and drop all loggers in the registry.
        // This is optional (only mandatory if using windows + async log).
        spdlog::shutdown();
    }

    // Exceptions will only be thrown upon failed logger or sink construction (not during logging).
    catch (const spdlog::spdlog_ex & ex)
    {
        std::printf("Log initialization failed: %s
", ex.what());
        return 1;
    }
}

#include "spdlog/sinks/stdout_color_sinks.h"
// or #include "spdlog/sinks/stdout_sinks.h" if no colors needed.
void stdout_logger_example()
{
    // Create color multi threaded logger.
    auto console = spdlog::stdout_color_mt("console");
    // or for stderr:
    // auto console = spdlog::stderr_color_mt("error-logger");
}

#include "spdlog/sinks/basic_file_sink.h"
void basic_example()
{
    // Create basic file logger (not rotated).
    auto my_logger = spdlog::basic_logger_mt("file_logger", "logs/basic-log.txt");
}

#include "spdlog/sinks/rotating_file_sink.h"
void rotating_example()
{
    // Create a file rotating logger with 5mb size max and 3 rotated files.
    auto rotating_logger = spdlog::rotating_logger_mt("some_logger_name", "logs/rotating.txt", 1048576 * 5, 3);
    int a = 100, b = 200;
    rotating_logger->error("error!");
    rotating_logger->info("a = {}, b = {}, a/b = {}, a%b = {}", a, b, a / b, a % b);
    rotating_logger->flush();
}

#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 daily_logger = spdlog::daily_logger_mt("daily_logger", "logs/daily.txt", 2, 30);
}

#include "spdlog/async.h"
void async_example()
{
    // Default thread pool settings can be modified *before* creating the async logger:
    // spdlog::init_thread_pool(32768, 1); // queue with max 32k items 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");

    for (int i = 1; i < 101; ++i)
    {
        async_file->info("Async message #{}", i);
    }
}

// Log binary data as hex.
// Many types of std::container<char> types can be used.
// Iterator 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.

#include "spdlog/fmt/bin_to_hex.h"
void binary_example()
{
    std::vector<char> buf;
    for (int i = 0; i < 80; i++)
    {
        buf.push_back(static_cast<char>(i & 0xff));
    }
    spdlog::info("Binary example: {}", spdlog::to_hex(buf));
    spdlog::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));
}

// Compile time log levels.
// define SPDLOG_ACTIVE_LEVEL to required level (e.g. SPDLOG_LEVEL_TRACE)
void trace_example()
{
    // trace from default logger
    SPDLOG_TRACE("Some trace message.. {} ,{}", 1, 3.23);
    // debug from default logger
    SPDLOG_DEBUG("Some debug message.. {} ,{}", 1, 3.23);

    // trace from logger object
    auto logger = spdlog::get("file_logger");
    SPDLOG_LOGGER_TRACE(logger, "another trace message");
}

// A logger with multiple sinks (stdout and file) - each with a different format and log level.
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");
}

// User defined types logging by implementing operator<<
#include "spdlog/fmt/ostr.h" // must be included
struct my_type
{
    int i;
    template<typename OStream>
    friend OStream& operator<<(OStream& os, const my_type& c)
    {
        return os << "[my_type i=" << c.i << "]";
    }
};

void user_defined_example()
{
    spdlog::info("user defined type: {}", my_type{ 14 });
}

// Custom error handler. Will be triggered on log failure.
void err_handler_example()
{
    // can be set globally or per logger(logger->set_error_handler(..))
    spdlog::set_error_handler([](const std::string& msg) { printf("*** Custom log error handler: %s ***
", msg.c_str()); });
}

// syslog example (linux/osx/freebsd)
#ifndef _WIN32
#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.");
}
#endif

// Android example.
#if defined(__ANDROID__)
#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.");
}

#endif

good good study, day day up.

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