C++ 日志库log4cpp使用详解

# Ubuntu/Debian
sudo apt-get install liblog4cpp5-dev

# CentOS/RHEL（需先配置 EPEL 源）
sudo yum install log4cpp-devel

# 下载源码
wget https://downloads.sourceforge.net/project/log4cpp/log4cpp-1.1.x%20%28new%29/log4cpp-1.1.3/log4cpp-1.1.3.tar.gz
tar zxvf log4cpp-1.1.3.tar.gz
cd log4cpp-1.1.3

# 编译安装
./configure --prefix=/usr/local
make
sudo make install

#include <log4cpp/Category.hh>
#include <log4cpp/PropertyConfigurator.hh>
#include <log4cpp/Appender.hh>
#include <log4cpp/FileAppender.hh>
#include <log4cpp/OstreamAppender.hh>
#include <log4cpp/Layout.hh>
#include <log4cpp/PatternLayout.hh>
#include <log4cpp/Priority.hh>

// 定义日志宏，自动添加文件名、函数名和行号
#define LOG_DEBUG(msg) \
    log4cpp::Category::getRoot() << log4cpp::Priority::DEBUG << "[" << __FILE__ << ":" << __LINE__ << "] " << __func__ << ": " << msg

#define LOG_INFO(msg) \
    log4cpp::Category::getRoot() << log4cpp::Priority::INFO << "[" << __FILE__ << ":" << __LINE__ << "] " << __func__ << ": " << msg

#define LOG_WARN(msg) \
    log4cpp::Category::getRoot() << log4cpp::Priority::WARN << "[" << __FILE__ << ":" << __LINE__ << "] " << __func__ << ": " << msg

#define LOG_ERROR(msg) \
    log4cpp::Category::getRoot() << log4cpp::Priority::ERROR << "[" << __FILE__ << ":" << __LINE__ << "] " << __func__ << ": " << msg

#define LOG_FATAL(msg) \
    log4cpp::Category::getRoot() << log4cpp::Priority::FATAL << "[" << __FILE__ << ":" << __LINE__ << "] " << __func__ << ": " << msg

// 带格式化输出的日志宏
#define LOG_DEBUG_F(fmt, ...) \
    do { \
        char buffer[1024]; \
        snprintf(buffer, sizeof(buffer), fmt, ##__VA_ARGS__); \
        LOG_DEBUG(buffer); \
    } while(0)

#define LOG_INFO_F(fmt, ...) \
    do { \
        char buffer[1024]; \
        snprintf(buffer, sizeof(buffer), fmt, ##__VA_ARGS__); \
        LOG_INFO(buffer); \
    } while(0)

// 初始化日志配置
void initLog() {
    // 创建控制台输出器
    log4cpp::Appender* consoleAppender = new log4cpp::OstreamAppender("console", &std::cout);
    
    // 创建文件输出器
    log4cpp::Appender* fileAppender = new log4cpp::FileAppender("file", "app.log");
    
    // 创建布局，设置日志格式
    log4cpp::PatternLayout* layout = new log4cpp::PatternLayout();
    // 格式说明：%d-日期 %p-优先级 %c-类别 %m-消息 %n-换行
    layout->setConversionPattern("%d{%Y-%m-%d %H:%M:%S} %p %c %m%n");
    
    // 为输出器设置布局
    consoleAppender->setLayout(layout);
    fileAppender->setLayout(layout);
    
    // 获取根日志类别，并添加输出器
    log4cpp::Category& root = log4cpp::Category::getRoot();
    root.addAppender(consoleAppender);
    root.addAppender(fileAppender);
    
    // 设置根日志的优先级（低于此级别的日志不输出）
    root.setPriority(log4cpp::Priority::DEBUG);
}

// 测试函数
void testLogFunction(int value) {
    LOG_DEBUG("进入测试函数");
    LOG_INFO_F("参数值为: %d", value);
    
    if (value < 0) {
        LOG_WARN("参数值为负数");
    }
    
    if (value == 0) {
        LOG_ERROR("参数值不能为零");
    }
}

int main() {
    // 初始化日志
    initLog();
    
    LOG_INFO("程序启动");
    
    // 测试日志输出
    testLogFunction(10);
    testLogFunction(-5);
    testLogFunction(0);
    
    LOG_INFO("程序退出");
    
    // 清理日志资源
    log4cpp::Category::shutdown();
    return 0;
}
    

g++ log4cpp_demo.cpp -o log_demo -llog4cpp -lpthread
./log_demo

# 根日志类别设置
log4cpp.rootCategory=DEBUG, console, file

# 控制台输出器配置
log4cpp.appender.console=org.apache.log4j.ConsoleAppender
log4cpp.appender.console.layout=org.apache.log4j.PatternLayout
log4cpp.appender.console.layout.ConversionPattern=%d{%Y-%m-%d %H:%M:%S} %p %c %m%n

# 文件输出器配置
log4cpp.appender.file=org.apache.log4j.FileAppender
log4cpp.appender.file.fileName=app.log
log4cpp.appender.file.layout=org.apache.log4j.PatternLayout
log4cpp.appender.file.layout.ConversionPattern=%d{%Y-%m-%d %H:%M:%S} %p %c [%-20F:%-4L] %-20M %m%n

# 模块特定日志配置（例如网络模块）
log4cpp.category.net=INFO, netfile
log4cpp.additivity.net=false
log4cpp.appender.netfile=org.apache.log4j.FileAppender
log4cpp.appender.netfile.fileName=net.log
log4cpp.appender.netfile.layout=org.apache.log4j.PatternLayout
log4cpp.appender.netfile.layout.ConversionPattern=%d %p %m%n

#include <log4cpp/Category.hh>
#include <log4cpp/PropertyConfigurator.hh>

// 日志宏定义（同上）
// ...

int main() {
    try {
        // 通过配置文件初始化
        log4cpp::PropertyConfigurator::configure("log4cpp.properties");
    } catch (log4cpp::ConfigureFailure& f) {
        std::cerr << "配置文件加载失败: " << f.what() << std::endl;
        return 1;
    }
    
    // 获取根日志类别
    log4cpp::Category& root = log4cpp::Category::getRoot();
    root.info("程序启动");
    
    // 获取网络模块日志类别
    log4cpp::Category& netCat = log4cpp::Category::getInstance("net");
    netCat.info("网络连接建立");
    
    // ... 其他日志输出
    
    log4cpp::Category::shutdown();
    return 0;
}

// 在代码中配置
log4cpp::RollingFileAppender* rollingAppender = 
    new log4cpp::RollingFileAppender("rolling", "rolling.log", 1024*1024, 5); // 1MB 每个，最多 5 个文件

log4cpp.appender.rolling=org.apache.log4j.RollingFileAppender
log4cpp.appender.rolling.fileName=rolling.log
log4cpp.appender.rolling.maxFileSize=1048576
log4cpp.appender.rolling.maxBackupIndex=5

log4cpp.appender.daily=org.apache.log4j.DailyRollingFileAppender
log4cpp.appender.daily.fileName=daily.log
log4cpp.appender.daily.datePattern='.'yyyy-MM-dd

// 代码中设置
log4cpp::Category::getRoot().setPriority(log4cpp::Priority::INFO);
log4cpp::Category::getInstance("debug.module").setPriority(log4cpp::Priority::DEBUG);