linux C/C++ 日志打印函数

//宏定义日志文件名

#define PROCESSNAME  "log_filename"


//当日志文件大于5M时，会删除该文件，该接口使用方法 参照printf
void WriteLog(const char *fm, ...)
{
    int buflen = 5120;
    char buf[buflen];
    int i = 0;
    memset(buf, 0, buflen);
    va_list args;
    va_start( args, fm );
    vsnprintf(buf, buflen, fm,args);
    va_end( args );

    printf("%s
", buf);
    FILE* logfile=NULL;
    char logpath[128] = {0};
    snprintf(logpath,sizeof(logpath),"/var/log/");
    if(access(logpath,0)!=0)
    {
        char cmdstr[256] = {0};
        sprintf(cmdstr,"mkdir -p %s",logpath);
        system(cmdstr);
    }

    char fname[256];
    char longtime[200];
    time_t t;
    memset(fname,0,sizeof(fname));
    time(&t);
    struct tm local = {0};
    localtime_r(&t, &local);
    sprintf(longtime,"%04d-%02d-%02d %02d:%02d:%02d", local.tm_year+1900,
            local.tm_mon+1, local.tm_mday, local.tm_hour, local.tm_min, local.tm_sec);
    sprintf(fname,"%s/%s", logpath, PROCESSNAME);
    for(i= 0; i < 3; i++)
    {
        logfile = fopen(fname, "ab");
        if(logfile)
            break;
        sleep(1);
    }
    if(logfile)
    {
        // 判断文件大小
        if (ftell(logfile) < 5*1024*1024)   // 5M
        {
            //日期时间
            const char* pTemp = longtime;
            fwrite(pTemp, 1, strlen(pTemp), logfile);
            fwrite(" ", 1, 1, logfile);
            //内容
            fwrite(buf, 1, strlen(buf), logfile);
            fwrite(" 
", 1, 3, logfile);
            fclose(logfile);
        }
        else
        {
            fclose(logfile);
            remove(fname);
        }
    }
}