转自：https://bbs.csdn.net/topics/391943383
#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#ifdef _MSC_VER

    #pragma warning(disable:4996)

    #include <windows.h>

    #include <io.h>

#else

    #include <unistd.h>

    #include <sys/time.h>

    #include <pthread.h>

    #define  CRITICAL_SECTION   pthread_mutex_t

    #define  _vsnprintf         vsnprintf

#endif

//Log{

#define MAXLOGSIZE 20000000

#define MAXLINSIZE 16000

#include <time.h>

#include <sys/timeb.h>

#include <stdarg.h>

char logfilename1[]="MyLog1.log";

char logfilename2[]="MyLog2.log";

static char logstr[MAXLINSIZE+];

char datestr[];

char timestr[];

char mss[];

CRITICAL_SECTION cs_log;

FILE *flog;

#ifdef _MSC_VER

void Lock(CRITICAL_SECTION *l) {

    EnterCriticalSection(l);

}

void Unlock(CRITICAL_SECTION *l) {

    LeaveCriticalSection(l);

}

#else

void Lock(CRITICAL_SECTION *l) {

    pthread_mutex_lock(l);

}

void Unlock(CRITICAL_SECTION *l) {

    pthread_mutex_unlock(l);

}

#endif

void LogV(const char *pszFmt,va_list argp) {

    struct tm *now;

    struct timeb tb;

    if (NULL==pszFmt||==pszFmt[]) return;

    _vsnprintf(logstr,MAXLINSIZE,pszFmt,argp);

    ftime(&tb);

    now=localtime(&tb.time);

    sprintf(datestr,"%04d-%02d-%02d",now->tm_year+,now->tm_mon+,now->tm_mday);

    sprintf(timestr,"%02d:%02d:%02d",now->tm_hour     ,now->tm_min  ,now->tm_sec );

    sprintf(mss,"%03d",tb.millitm);

    printf("%s %s.%s %s",datestr,timestr,mss,logstr);

    flog=fopen(logfilename1,"a");

    if (NULL!=flog) {

        fprintf(flog,"%s %s.%s %s",datestr,timestr,mss,logstr);

        if (ftell(flog)>MAXLOGSIZE) {

            fclose(flog);

            if (rename(logfilename1,logfilename2)) {

                remove(logfilename2);

                rename(logfilename1,logfilename2);

            }

        } else {

            fclose(flog);

        }

    }

}

void Log(const char *pszFmt,...) {

    va_list argp;

    Lock(&cs_log);

    va_start(argp,pszFmt);

    LogV(pszFmt,argp);

    va_end(argp);

    Unlock(&cs_log);

}

//Log}

int main(int argc,char * argv[]) {

    int i;

#ifdef _MSC_VER

    InitializeCriticalSection(&cs_log);

#else

    pthread_mutex_init(&cs_log,NULL);

#endif

    for (i=;i<;i++) {

        Log("This is a Log %04d from FILE:%s LINE:%d\n",i, __FILE__, __LINE__);

    }

#ifdef _MSC_VER

    DeleteCriticalSection(&cs_log);

#else

    pthread_mutex_destroy(&cs_log);

#endif

    return ;

}

//1-79行添加到你带main的.c或.cpp的那个文件的最前面

//81-86行添加到你的main函数开头

//90-94行添加到你的main函数结束前

//在要写LOG的地方仿照第88行的写法写LOG到文件MyLog1.log中