[glog]_[C/C++]_[使用glog来记录日志]

glog 快速使用教程

场景

1.大部分程序由函数组成, 每个函数执行一段设计好的逻辑, 但是大部分的时候有可能出现意料之外的值, 这时候就很想知道这种意料以外的值是如何产生的, 这就需要一个函数调用和参数跟踪, 日志正好发挥作用.

2.调试多线程程序时某些函数执行顺序可能出现期望之外的顺序，或者需要知道出问题时线程执行的顺序，而Debug程序并不能同时Debug多个线程的函数调用, 而且会影响线程的竞争导致bug无法重现，这时只能用日志.

3.在客户使用软件时, 经常需要分析用户的使用习惯和行为, 从而根据用户行为习惯来重点推荐产品, 这时候就需要历史日志.

说明

1.glog只支持utf8编码的日志文件.

2.glog的严重程度级别只支持4种, INFO, WARNING, ERROR, and FATAL. 也就是LOG(XXX); DLOG用来记录DEBUG模式的日志, 在Release模式下会未定义,不用担心性能问题(#ifndef NDEBUG). 默认情况下会把 ERROR 或 FATAL 级别输出到stderr.

3.条件或偶发性日志, 可允许指定变量满足特定值才输出日志. 比如a>10,每请求10次日志才输出一次,限制输出的前几次. LOG_IF,LOG_EVERY_N,LOG_IF_EVERY_N,LOG_FIRST_N. 如果只需要在Debug模式下输出. DLOG,DLOG_IF,DLOG_EVERY_N.

4.检查宏用来检查期待的条件, 如果不满足条件,就会中断程序.CHECK,CHECK_NE,CHECK_EQ,CHECK_EQ,CHECK_NOTNULL,CHECK_STREQ,CHECK_STRNE,CHECK_STRCASEEQ,CHECK_STRCASENE 等等. 如果不想让程序中断的话, 这些宏很少用.

5.设置标记, 可以通过命令行设置参数, 比如 ./your_application –logtostderr=1, 但是要使用 Google gflags library. 如果没有使用gflags库, 可以使用环境变量设置. GLOG_logtostderr=1, FLAGS_v=1. 或者在代码里设置 FLAGS_*.

6.Raw Logging, 使用头文件

例子

1. 注意, 这个例子只是产生输出, 如果想把日志输出到文件, 那么把 FLAGS_logtostderr=false.

// test-log.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

// 使用Windows自带的SEVERITIES定义
#define GLOG_NO_ABBREVIATED_SEVERITIES
#include <Windows.h>

#include <glog/logging.h>
#include <glog/raw_logging.h>

static char* ConvertUnicodeToUtf8(const wchar_t* unicode)
{
    if(unicode == NULL)
    {
        return strdup("\0");
    }

    int len;
    len = WideCharToMultiByte(CP_UTF8, 0,unicode, -1, NULL, 0, NULL, NULL);
    char *szUtf8 = (char*)malloc(len + 1);
    memset(szUtf8, 0, len + 1);
    WideCharToMultiByte(CP_UTF8, 0,unicode, -1, szUtf8, len, NULL,NULL);
    return szUtf8;
}

void TestLogSeverityLevel()
{
    LOG(INFO) << "TestLogSeverityLevel the INFO text";
    DLOG(INFO) << "TestLogSeverityLevel the DEBUG text";
    LOG(ERROR) << "TestLogSeverityLevel the ERROR text1";
    LOG(WARNING) << "TestLogSeverityLevelthe warning text";
    LOG(ERROR) << "TestLogSeverityLevel the ERROR text2";
    // DLOG(FATAL) << "DEBUG FATAL"; // 会产生一个abort中断之前先输出到日志
}

void TestSettingFlags()
{
    // 日志文件格式
    ///tmp/<program name>.<hostname>.<user name>.log.<severity level>.<date>.<time>.<pid>
    // test-log.exe.APPLE-PC.apple.log.INFO.20161230-155337.2472

    // 注意,文件路径编码必须是GB2312,不然不识别以下中文路径,如果文件不是本地编码(ANSI),那么需要转换为ANSI编码.
    // 设置日志目录,必须是ANSI(中文系统即GB2312)编码,不支持UNICODE
    // 该目录必须存在,不然生成不了日志文件.
    FLAGS_logtostderr = true; // 不输出到文件,输出到stderr.
    FLAGS_log_dir = "E:\\新建文件夹\\";
    FLAGS_max_log_size = 20; // 设置最大日志文件大小.
}

void TestConditionalAndOccasionalLogging()
{
    for(int i = 0; i< 100;++i)
    {
        LOG_IF(INFO,i%10 == 0) << "LOG_IF i is " << i; // 每10次输出一次.
        LOG_EVERY_N(INFO,10) << " LOG_EVERY_N i is " << i <<  " Got the " << google::COUNTER; // 也是每间隔10次输出
        LOG_FIRST_N(INFO, 20) << "LOG_FIRST_N i is " << i << " Got the " << google::COUNTER; // 输出前20个
    }
}

void TestCHECKMacros()
{
    std::string first = "abcd";
    std::string second = "AbCd";
    CHECK_EQ(first,second); //产生一个中断之前先输出到日志
}

int _tmain(int argc, _TCHAR* argv[])
{
    // Initialize Google's logging library.
    // glog保存的文件时UTF-8格式编码,所以需要转码需要记录的字符串为UTF-8,转换为utf8.

    char* argv0 = ConvertUnicodeToUtf8(argv[0]);
    google::InitGoogleLogging(argv0);

    TestSettingFlags();
    TestLogSeverityLevel();
    TestConditionalAndOccasionalLogging();
    TestCHECKMacros();

    // 日志内容
    //Log file created at: 2016/12/30 15:53:37
    //Running on machine: APPLE-PC
    //Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg
    //I1230 15:53:37.337400  5456 test-log.cpp:35] the same file

    //google::FlushLogFiles(google::GLOG_ERROR);
    google::ShutdownGoogleLogging();
    return 0;
}

输出

I1231 20:33:15.303700  5852 test-log.cpp:31] TestLogSeverityLevel the INFO text
I1231 20:33:15.303700  5852 test-log.cpp:32] TestLogSeverityLevel the DEBUG text

E1231 20:33:15.303700  5852 test-log.cpp:33] TestLogSeverityLevel the ERROR text
1
W1231 20:33:15.303700  5852 test-log.cpp:34] TestLogSeverityLevelthe warning tex
t
E1231 20:33:15.303700  5852 test-log.cpp:35] TestLogSeverityLevel the ERROR text
2
I1231 20:33:15.303700  5852 test-log.cpp:57] LOG_IF i is 0
I1231 20:33:15.303700  5852 test-log.cpp:58]  LOG_EVERY_N i is 0 Got the 1
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 0 Got the 1
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 1 Got the 2
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 2 Got the 3
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 3 Got the 4
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 4 Got the 5
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 5 Got the 6
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 6 Got the 7
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 7 Got the 8
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 8 Got the 9
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 9 Got the 10
I1231 20:33:15.303700  5852 test-log.cpp:57] LOG_IF i is 10
I1231 20:33:15.303700  5852 test-log.cpp:58]  LOG_EVERY_N i is 10 Got the 11
I1231 20:33:15.303700  5852 test-log.cpp:59] LOG_FIRST_N i is 10 Got the 11
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 11 Got the 12
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 12 Got the 13
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 13 Got the 14
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 14 Got the 15
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 15 Got the 16
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 16 Got the 17
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 17 Got the 18
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 18 Got the 19
I1231 20:33:15.319300  5852 test-log.cpp:59] LOG_FIRST_N i is 19 Got the 20
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 20
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 20 Got the 21
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 30
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 30 Got the 31
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 40
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 40 Got the 41
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 50
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 50 Got the 51
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 60
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 60 Got the 61
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 70
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 70 Got the 71
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 80
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 80 Got the 81
I1231 20:33:15.319300  5852 test-log.cpp:57] LOG_IF i is 90
I1231 20:33:15.319300  5852 test-log.cpp:58]  LOG_EVERY_N i is 90 Got the 91
F1231 20:33:15.319300  5852 test-log.cpp:67] Check failed: first == second (abcd
 vs. AbCd)
*** Check failure stack trace: ***

参考

1.源码的doc/glog.html