time_t tm timeval 和 时间字符串的转换方法

struct tm {     int tm_sec;   /* seconds after the minute - [0,59] */     int tm_min;   /* minutes after the hour - [0,59] */     int tm_hour;  /* hours since midnight - [0,23] */     int tm_mday;  /* day of the month - [1,31] */     int tm_mon;   /* months since January - [0,11] */     int tm_year;  /* years since 1900 */     int tm_wday;  /* days since Sunday - [0,6] */     int tm_yday;  /* days since January 1 - [0,365] */     int tm_isdst;  /* daylight savings time flag */     }; 

struct timeval {     time_t    tv_sec;   /* seconds */     suseconds_t  tv_usec; /* microseconds */ };

time_t time(time_t *t); //取得从1970年1月1日至今的秒数 char *asctime(const struct tm *tm); //将结构中的信息转换为真实世界的时间，以字符串的形式显示 char *ctime(const time_t *timep); //将timep转换为真是世界的时间，以字符串显示，它和asctime不同就在于传入的参数形式不一样 struct tm *gmtime(const time_t *timep); //将time_t表示的时间转换为没有经过时区转换的UTC时间，是一个struct tm结构指针  struct tm *localtime(const time_t *timep); //和gmtime类似，但是它是经过时区转换的时间。 time_t mktime(struct tm *tm); //将struct tm 结构的时间转换为从1970年至今的秒数 int gettimeofday(struct timeval *tv, struct timezone *tz); //返回当前距离1970年的秒数和微妙数，后面的tz是时区，一般不用 double difftime(time_t time1, time_t time2); //返回两个时间相差的秒数 

time_t t; //秒时间 tm* local; //本地时间  tm* gmt;  //格林威治时间 char buf[128]= {0};  t = time(NULL); //或者time(&t);//获取目前秒时间 local = localtime(&t); //转为本地时间 strftime(buf, 64, "%Y-%m-%d %H:%M:%S", local); std::cout << buf << std::endl;  gmt = gmtime(&t);//转为格林威治时间 strftime(buf, 64, "%Y-%m-%d %H:%M:%S", gmt); std::cout << buf << std::endl; 

 tm tm_; time_t t_; char buf[128]= {0};  strcpy(buf, "2012-01-01 14:00:00"); strptime(buf, "%Y-%m-%d %H:%M:%S", &tm_); //将字符串转换为tm时间 tm_.tm_isdst = -1; t_ = mktime(&tm_); //将tm时间转换为秒时间 t_ += 3600; //秒数加3600  tm_ = *localtime(&t_);//输出时间 strftime(buf, 64, "%Y-%m-%d %H:%M:%S", &tm_); std::cout << buf << std::endl;  

time_t StringToDatetime(char *str) {   tm tm_;   int year, month, day, hour, minute,second;   sscanf(str,"%d-%d-%d %d:%d:%d", &year, &month, &day, &hour, &minute, &second);   tm_.tm_year = year-1900;   tm_.tm_mon  = month-1;   tm_.tm_mday = day;   tm_.tm_hour = hour;   tm_.tm_min  = minute;   tm_.tm_sec  = second;   tm_.tm_isdst = 0;    time_t t_ = mktime(&tm_); //已经减了8个时区   return t_; //秒时间 } 

struct timeval start_time, over_time, consume_time;gettimeofday(&over_time, NULL);//get the current timestart_time = over_time; do something.....gettimeofday(&over_time, NULL);timeval_subtract(&consume_time, &start_time, &over_time);//计算时间差104./**    * 计算两个时间的间隔，得到时间差    * @param struct timeval* resule 返回计算出来的时间    * @param struct timeval* x 需要计算的前一个时间    * @param struct timeval* y 需要计算的后一个时间    * return -1 failure ,0 success  **/ timeval_subtract(struct timeval* result, struct timeval* x, struct timeval* y)  {     if ( x->tv_sec>y->tv_sec )          return -1;       if ( (x->tv_sec==y->tv_sec) && (x->tv_usec>y->tv_usec) )          return -1;       result->tv_sec = ( y->tv_sec-x->tv_sec );     result->tv_usec = ( y->tv_usec-x->tv_usec );       if (result->tv_usec<0)     {          result->tv_sec--;          result->tv_usec+=1000000;     }       return 0;  }