使用 C++ 获取 Unix 时间戳
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/6012663/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Get Unix timestamp with C++
提问by 2rs2ts
How do I get a uintunix timestamp in C++? I've googled a bit and it seems that most methods are looking for more convoluted ways to represent time. Can't I just get it as a uint?
如何uint在 C++ 中获得unix 时间戳？我用谷歌搜索了一下，似乎大多数方法都在寻找更复杂的方式来表示时间。我不能把它当作一个uint吗？
回答by Tony Delroy
C++20 introduced a guarantee that time_since_epochwill be relative to the UNIX epoch, and gives this example (distilled to relevant code, and in units of seconds rather than hours):
C++20 引入了一个time_since_epoch与 UNIX 时代相关的保证，并给出了这个例子（提炼为相关代码，以秒而不是小时为单位）：
#include <iostream>
#include <chrono>
int main()
{
const auto p1 = std::chrono::system_clock::now();
std::cout << "seconds since epoch: "
<< std::chrono::duration_cast<std::chrono::seconds>(
p1.time_since_epoch()).count() << '\n';
}
Using C++17 or earlier, time()is the simplest function - seconds since Epoch, which for Linux and UNIX at least would be the UNIX epoch. Linux manpage here.
使用 C++17 或更早版本，time()是最简单的函数 - 自 Epoch 以来的秒数，对于 Linux 和 UNIX 至少将是 UNIX epoch。此处为Linux 联机帮助页。
The cppreference page linked above gives this example:
上面链接的 cppreference 页面给出了这个例子：
#include <ctime>
#include <iostream>
int main()
{
std::time_t result = std::time(nullptr);
std::cout << std::asctime(std::localtime(&result))
<< result << " seconds since the Epoch\n";
}
回答by wilhelmtell
#include<iostream>
#include<ctime>
int main()
{
std::time_t t = std::time(0); // t is an integer type
std::cout << t << " seconds since 01-Jan-1970\n";
return 0;
}
回答by MSalters
The most common advice is wrong, you can't just rely on time(). That's used for relative timing: ISO C++ doesn't specify that 1970-01-01T00:00Zis time_t(0)
最常见的建议是错误的，你不能仅仅依赖time(). 这用于相对时间：ISO C++ 没有指定1970-01-01T00:00Z是time_t(0)
What's worse is that you can't easily figure it out, either. Sure, you can find the calendar date of time_t(0)with gmtime, but what are you going to do if that's 2000-01-01T00:00Z? How many seconds were there between 1970-01-01T00:00Zand 2000-01-01T00:00Z? It's certainly no multiple of 60, due to leap seconds.
更糟糕的是，您也无法轻松弄清楚。当然，您可以找到time_t(0)with的日历日期gmtime，但是如果是，您将怎么办2000-01-01T00:00Z？1970-01-01T00:00Z和之间有多少秒2000-01-01T00:00Z？由于闰秒，它肯定不是 60 的倍数。
回答by anijhaw
#include <iostream>
#include <sys/time.h>
using namespace std;
int main ()
{
unsigned long int sec= time(NULL);
cout<<sec<<endl;
}
回答by Tharwen
As this is the first result on google and there's no C++20 answer yet, here's how to use std::chrono to do this:
由于这是 google 上的第一个结果，而且还没有 C++20 答案，这里是如何使用 std::chrono 来做到这一点：
#include <chrono>
//...
using namespace std::chrono;
int64_t timestamp = duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
In versions of C++ before 20, system_clock's epoch being Unix epoch is a de-facto convention, but it's not standardized. If you're not on C++20, use at your own risk.
在 20 之前的 C++ 版本中，system_clock 的纪元是 Unix 纪元是事实上的约定，但它没有标准化。如果您使用的不是 C++20，请自担风险。
回答by davecb
Windows uses a different epoch and time units: see Convert Windows Filetime to second in Unix/Linux
Windows 使用不同的纪元和时间单位：参见 Convert Windows Filetime to second in Unix/Linux
What std::time() returns on Windows is (as yet) unknown to me (;-))
我不知道 std::time() 在 Windows 上返回的内容（迄今为止）（;-)）
回答by xinthose
I created a global define with more information:
我创建了一个包含更多信息的全局定义：
#include <iostream>
#include <ctime>
#include <iomanip>
#define INFO std::cout << std::put_time(std::localtime(&time_now), "%y-%m-%d %OH:%OM:%OS") << " [INFO] " << __FILE__ << "(" << __FUNCTION__ << ":" << __LINE__ << ") >> "
#define ERROR std::cout << std::put_time(std::localtime(&time_now), "%y-%m-%d %OH:%OM:%OS") << " [ERROR] " << __FILE__ << "(" << __FUNCTION__ << ":" << __LINE__ << ") >> "
static std::time_t time_now = std::time(nullptr);
Use it like this:
像这样使用它：
INFO << "Hello world" << std::endl;
ERROR << "Goodbye world" << std::endl;
Sample output:
示例输出：
16-06-23 21:33:19 [INFO] src/main.cpp(main:6) >> Hello world
16-06-23 21:33:19 [ERROR] src/main.cpp(main:7) >> Goodbye world
Put these lines in your header file. I find this very useful for debugging, etc.
将这些行放在您的头文件中。我发现这对于调试等非常有用。
