std::mktime
Defined in header <ctime> | | |
|---|---|---|
std::time_t mktime( std::tm* time ); | | |
将本地日历时间作为time_t对象。time->tm_wday和time->tm_yday被忽视了。中的值time被允许超出正常范围。
负值time->tm_isdst原因mktime尝试确定夏令时间是否有效。
如果转换成功，则time对象被修改。所有领域time更新以适应它们的适当范围。time->tm_wday和time->tm_yday使用其他字段中可用的信息重新计算。
参数
time | - | pointer to a std::tm object specifying local calendar time to convert |
|---|
返回值
作为一个时代std::time_t在成功或-1如果time不能表示为std::time_t对象。
注记
如果std::tm对象是从std::get_time或POSIX短时的价值tm_isdst是不确定的，需要在调用mktime...
例
显示100个月前的时间。
二次
#include <iostream>
#include <iomanip>
#include <ctime>
#include <stdlib.h>
int main()
{
setenv("TZ", "/usr/share/zoneinfo/America/New_York", 1); // POSIX-specific
std::time_t t = std::time(NULL);
std::tm tm = *std::localtime(&t);
std::cout << "Today is " << std::put_time(&tm, "%c %Z")
<< " and DST is " << (tm.tm_isdst ? "in effect" : "not in effect") << '\n';
tm.tm_mon -= 100; // tm_mon is now outside its normal range
std::mktime(&tm); // tm_dst is not set to -1; today's DST status is used
std::cout << "100 months ago was " << std::put_time(&tm, "%c %Z")
<< " and DST was " << (tm.tm_isdst ? "in effect" : "not in effect") << '\n';
}二次
产出：
二次
Today is Fri Apr 22 11:40:36 2016 EDT and DST is in effect
100 months ago was Sat Dec 22 10:40:36 2007 EST and DST was not in effect二次
另见
localtime | converts time since epoch to calendar time expressed as local time (function) |
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c mktime文档
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