C ++：如何获取实际时间与时间和本地时间？ [英] C++: how to get the actual time with time and localtime?

问题描述

我正在寻找一种方法来节省时间在HH :: MM :: SS时尚在C + +。我在这里看到他们是很多解决方案，经过一番研究，我选择了时间和 localtime 。但是， localtime 函数似乎有点棘手，因为它说：

对localtime和gmtime的所有调用使用相同的静态结构，因此
每个调用覆盖上一次调用的结果。

这会导致的问题显示在下面的代码段中：

  #include< ctime> 
 #include< iostream> 
 using namespace std; 
 
 int main（）{
 time_t t1 = time（0）; // get time now 
 struct tm * now = localtime（& t1）; 
 
 std :: cout<< t1 < std :: endl; 
 sleep（2）; 
 time_t t2 = time（0）; // get time now 
 struct tm * now2 = localtime（& t2）; 
 std :: cout<< t2 < std :: endl; 
 
 cout<< （now-> tm_year + 1900）< ' - '
< （now-> tm_mon + 1）< ' - '
<< now-> tm_mday<< ，
<< now-> tm_hour<< ：<< now-> tm_min<< ：<< now-> tm_sec 
<< endl; 
 
 cout<< （now2-> tm_year + 1900）< ' - '
<< （now2-> tm_mon + 1）< ' - '
<< now2-> tm_mday<< ，
<< now2-> tm_hour<< ：<< now2-> tm_min<< ：<< now2-> tm_sec 
<< endl; 
} 
  

典型输出为：

  1320655946 
 1320655948 
 2011-11-7，9:52:28 
 2011-11-7，9:52： 28 
  

可以看到， time_t 时间戳是正确的，但是本地时间混乱了一切。

我的问题是：如何将时间戳类型 time_t 转换成人类可读的时间？如果你担心 localtime 和

解决方案

> gmtime ，有 localtime_r 和 gmtime_r 可以处理多个呼叫。 >

当按照你的喜好格式化时间时，检查函数 strftime 。

I'm looking for a way to save the time in a HH::MM::SS fashion in C++. I saw here that they are many solutions and after a little research I opted for time and localtime. However, it seems like the localtime function is a little tricky, since it says:

All calls to localtime and gmtime use the same static structure, so each call overwrites the results of the previous call.

The problem that this causes is shown in the next snippet of code:

#include <ctime>
#include <iostream>
using namespace std;

int main() {
time_t t1 = time(0);   // get time now
struct tm * now = localtime( & t1 );

std::cout << t1 << std::endl;
sleep(2);
time_t t2 = time(0);   // get time now
struct tm * now2 = localtime( & t2 );
std::cout << t2 << std::endl;

cout << (now->tm_year + 1900) << '-'
     << (now->tm_mon + 1) << '-'
     <<  now->tm_mday << ", "
     << now->tm_hour << ":" << now->tm_min << ":" << now->tm_sec
     << endl;

cout << (now2->tm_year + 1900) << '-'
     << (now2->tm_mon + 1) << '-'
     <<  now2->tm_mday << ", "
     << now2->tm_hour << ":" << now2->tm_min << ":" << now2->tm_sec
     << endl;
}

A typical output for this is:

1320655946
1320655948
2011-11-7, 9:52:28
2011-11-7, 9:52:28

So as you can see, the time_t timestamps are correct, but the localtime messes everything up.

My question is: how do I convert a timestamp ot type time_t into a human-readable time?

解决方案

If you are worried about reentrancy in localtime and gmtime, there is localtime_r and gmtime_r which can handle multiple calls.

When it comes to formatting the time to your liking, check the function strftime.

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