C++有关时间代码

0. 时间日期

tm结构体

/* ISO C `broken-down time' structure.  */
struct tm
{
  int tm_sec;           /* Seconds. [0-60] (1 leap second) */
  int tm_min;           /* Minutes. [0-59] */
  int tm_hour;          /* Hours.   [0-23] */
  int tm_mday;          /* Day.     [1-31] */
  int tm_mon;           /* Month.   [0-11] */
  int tm_year;          /* Year - 1900.  */
  int tm_wday;          /* Day of week. [0-6] */
  int tm_yday;          /* Days in year.[0-365] */
  int tm_isdst;         /* DST.     [-1/0/1]*/

# ifdef __USE_MISC
  long int tm_gmtoff;       /* Seconds east of UTC.  */
  const char *tm_zone;      /* Timezone abbreviation.  */
# else
  long int __tm_gmtoff;     /* Seconds east of UTC.  */
  const char *__tm_zone;    /* Timezone abbreviation.  */
# endif
};

栗子代码1:

#include "time.h"
#include <iostream>

int main() {

    time_t now = time(0);
    tm *ltm = localtime(&now);

    std::cout << "year: " << 1900 + ltm->tm_year << std::endl;
    std::cout << "month: " << 1 + ltm->tm_mon << std::endl;
    std::cout << "day: " << ltm->tm_mday << std::endl;
    std::cout << "time: " << ltm->tm_hour << std::endl;
    std::cout << ltm->tm_min << ":";
    std::cout << ltm->tm_sec << std::endl;

    return 0;
}

栗子代码2 返回string:

std::string GetDateTimeNow() {
    time_t now = time(0);
    tm *ltm = localtime(&now);

    std::string str = "当前时间" + std::to_string(1900 + ltm->tm_year) + "年"
                        + std::to_string(1 + ltm->tm_mon) + "月"
                        + std::to_string(ltm->tm_mday) + "日"
                        + std::to_string(ltm->tm_hour) + "时"
                        + std::to_string(ltm->tm_min) + "分";

    return str;
}

1. 评估代码运行时间

time.h

#include "time.h"
#include <iostream>

int main() {
    
    clock_t start, finish;
    double duration;
    
    start = clock();
    // do sth
    finish = clock();
    duration = (double)(finish - start) / CLOCKS_PER_SEC;
    std::cout << "time : " << duration << std::endl;

    return 0;
}

这里输出CLOCKS_PER_SEC等于1000000