17_c/c++开源库 easylogging日志库

1.简介与安装

简介:
EasyLogging的主要特点包括：

简单易用：EasyLogging的API设计简洁明了，使用起来非常方便。开发者只需包含头文件并初始化库，即可开始记录日志。
高效性：EasyLogging采用异步日志记录方式，将日志信息的写入操作与程序的主线程分离，从而避免了日志记录对程序性能的影响。
线程安全：EasyLogging支持多线程环境下的日志记录，内部采用了锁机制来保证线程安全。
可配置性：EasyLogging提供了丰富的配置选项，允许开发者根据需要自定义日志记录的级别、格式、输出目标等。
跨平台兼容：EasyLogging支持多种操作系统和编译器，具有良好的跨平台兼容性。

安装

sudo apt install libeasyloggingpp-dev

使用

编译依赖
pkg-config --cflags --libs easyloggingpp

没错,你没有看错, ubuntu20.04上默认安装libeasyloggingpp-dev 没有提示任何 ld链接选项.
通过github 下载最新的源代码, 编译安装, 也是一样.
但实际上, ld链接时提示错误:

g++ -o 1_easylogging_日志.out 1_easylogging_日志.o
/bin/ld: 1_easylogging_日志.o: in function `main':
/home/liuj/1_data/3_cpp-practice/21_开源库/17_easylogging日志库/1_easylogging_日志.cc:7: undefined reference to `el::base::Writer::construct(int, char const*, ...)'
/bin/ld: 1_easylogging_日志.o: in function `__static_initialization_and_destruction_0(int, int)':
/home/liuj/1_data/3_cpp-practice/21_开源库/17_easylogging日志库/1_easylogging_日志.cc:4: undefined reference to `el::base::Storage::Storage(std::shared_ptr const&)'
/bin/ld: 1_easylogging_日志.o: in function `el::LogBuilder::LogBuilder()':
/usr/include/easylogging++.h:2197: undefined reference to `el::base::utils::OS::termSupportsColor()'
/bin/ld: 1_easylogging_日志.o: in function `el::base::Writer::~Writer()':
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解决方法1:
将easylogging++.cc 源代码以头文件方式导入

#include 
#include 
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解决方法2:
将libeasylogging++.cc 编译为动态库 libeasylogging.so, 拷贝到系统lib目录下 /usr/lib
本文使用的是: 解决方法2
1. 在scons中检测库/usr/lib/libeasylogging.so 存在,不存在则拷贝
2. 链接选项: -leasylogging

2.实例

1.代码

1_easylogging_日志.cc

#include 
// #include 

INITIALIZE_EASYLOGGINGPP    // 初始化宏，有且只能使用一次

int main(int argc, char* argv[]) {
   LOG(INFO) << "My first info log using default logger";
   return 0;
}

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---

my_log.conf

* GLOBAL:
    ENABLED                 =   true
    TO_FILE                 =   true
    TO_STANDARD_OUTPUT      =   true
    FORMAT                  =   "[%level | %datetime] | %msg"
    FILENAME                =   "log/log_%datetime{%Y%M%d}.log"
    MILLISECONDS_WIDTH      =   3
    PERFORMANCE_TRACKING    =   false
    MAX_LOG_FILE_SIZE       =   2097152 ## 2MB
    LOG_FLUSH_THRESHOLD     =   0

* TRACE:
    FILENAME                =   "log/trace_log_%datetime{%Y%M%d}.log"

* DEBUG:
    FILENAME                =   "log/debug_log_%datetime{%Y%M%d}.log"

* FATAL:
    ENABLED                 =   false

* ERROR:
    FILENAME                =   "log/error_log_%datetime{%Y%M%d}.log"

* WARNING:
    FILENAME                =   "log/warning_log_%datetime{%Y%M%d}.log"

* INFO:
    FILENAME                =   "log/info_log_%datetime{%Y%M%d}.log"

* VERBOSE:
    ENABLED                 =   false
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2_easylogging_读取配置.cc

#include "easylogging++.h"

INITIALIZE_EASYLOGGINGPP

int main(int argc, char** argv)
{
	el::Configurations conf("my_log.conf");
	el::Loggers::reconfigureAllLoggers(conf);

	LOG(TRACE)   << "***** trace log  *****";
	LOG(DEBUG)   << "***** debug log  *****";
	LOG(ERROR)   << "***** error log  *****";
	LOG(WARNING) << "***** warning log  *****";
	LOG(INFO)    << "***** info log  *****";

	system("pause");
	return 0;
}
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---

3_easylogging_条件打印.cc

#include "easylogging++.h"

INITIALIZE_EASYLOGGINGPP

int main(int argc, char **argv)
{
	int i = 0;
	while (i++ < 100)
	{
		//  条件日志
		LOG_IF((i % 5 == 0), INFO) << " %5 == 0" << i;
		// 每n次记录一次
		LOG_EVERY_N(20, INFO) << "LOG_EVERY_N i = " << i;
		// 当计数达到n次之后，才开始记录日志
		LOG_AFTER_N(6, INFO) << "LOG_AFTER_N i = " << i;
		// 当记录次数达到n次之后，就不再记录
		LOG_N_TIMES(1, INFO) << "LOG_N_TIMES i = " << i;
	}

	return 0;
}

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2.scons编译

SConstruct

import os
env = Environment()
env["PROGSUFFIX"] = ".out"            # 可执行文件后缀.out
env["CCFLAGS"] = " -g3 -O0 -Wall"     # gdb 调试

def build_share_lib():
    SharedLibrary("easylogging","easylogging++.cc")
    # Install(target="/usr/lib",source=['easylogging.so'])  # --NG
    # Command("/usr/lib/libeasylogging.so","libeasylogging.so","sudo cp -rf libeasylogging.so /usr/lib/")    # --NG
    # Command("./lib/libeasylogging.so","libeasylogging.so","cp -rf libeasylogging.so ./lib/libeasylogging.so")  # --OK
    if not os.path.exists("/usr/lib/libeasylogging.so"):
        os.system("sudo cp -rf libeasylogging.so /usr/lib/libeasylogging.so") # --ok
        print("copy libeasylogging.so /usr/lib ---ok")
        # os.system("sudo install libeasylogging.so /usr/lib") # --ok

## 模板2
build_share_lib()
env["LIBS"] = ["easylogging"]
env.Program("1_easylogging_日志.cc", LIBS=["easylogging"],LIBPATH='.') # fix:scons无法优先编译 动态库easylogging.so
env.Program("2_easylogging_读取配置.cc")
env.Program("3_easylogging_条件打印.cc")
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scons

scons: Reading SConscript files …
scons: done reading SConscript files.
scons: Building targets …
g++ -o 1_easylogging_日志.o -c -g3 -O0 -Wall 1_easylogging_日志.cc
g++ -o easylogging++.os -c -fPIC easylogging++.cc
g++ -o libeasylogging.so -shared easylogging++.os
g++ -o 1_easylogging_日志.out 1_easylogging_日志.o -L. -leasylogging
g++ -o 2_easylogging_读取配置.o -c -g3 -O0 -Wall 2_easylogging_读取配置.cc
g++ -o 2_easylogging_读取配置.out 2_easylogging_读取配置.o -leasylogging
g++ -o 3_easylogging_条件打印.o -c -g3 -O0 -Wall 3_easylogging_条件打印.cc
g++ -o 3_easylogging_条件打印.out 3_easylogging_条件打印.o -leasylogging
scons: done building targets.

3.运行

./1_easylogging_日志.out

2024-04-24 00:45:55,850 INFO [default] My first info log using default logger

./2_easylogging_读取配置.out

[TRACE | 2024-04-24 00:45:58,466] | ***** trace log  *****
[DEBUG | 2024-04-24 00:45:58,466] | ***** debug log  *****
[ERROR | 2024-04-24 00:45:58,466] | ***** error log  *****
[WARNING | 2024-04-24 00:45:58,466] | ***** warning log  *****
[INFO | 2024-04-24 00:45:58,466] | ***** info log  *****
sh: pause: command not found
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./3_easylogging_条件打印.out

2024-04-24 00:46:03,897 INFO [default] LOG_N_TIMES i = 1
2024-04-24 00:46:03,897 INFO [default]  %5 == 05
2024-04-24 00:46:03,897 INFO [default] LOG_AFTER_N i = 7
2024-04-24 00:46:03,897 INFO [default] LOG_AFTER_N i = 8
2024-04-24 00:46:03,897 INFO [default] LOG_AFTER_N i = 9
2024-04-24 00:46:03,897 INFO [default]  %5 == 010
2024-04-24 00:46:03,897 INFO [default] LOG_AFTER_N i = 10
2024-04-24 00:46:03,897 INFO [default] LOG_AFTER_N i = 11
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 12
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 13
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 14
2024-04-24 00:46:03,898 INFO [default]  %5 == 015
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 15
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 16
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 17
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 18
2024-04-24 00:46:03,898 INFO [default] LOG_AFTER_N i = 19
2024-04-24 00:46:03,898 INFO [default]  %5 == 020
2024-04-24 00:46:03,898 INFO [default] LOG_EVERY_N i = 20
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gitee 在线代码

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