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}", );
     spdlog::critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", );
     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(); // create ring buffer with capacity of 10  messages
     for (int i = ; i < ; 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());

         // 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\n", ex.what());
         return ;
     }
 }

 #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",  * , );
     int a = , b = ;
     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", , );
 }

 #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 = ; i < ; ++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 = ; i < ; 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) + ));
     // 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.. {} ,{}", , 3.23);
     // debug from default logger
     SPDLOG_DEBUG("Some debug message.. {} ,{}", , 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{  });
 }

 // 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 ***\n", 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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