CODEWITHSUNDEEP
c++timestamp
AKIWEB
AKIWEB

Reputation: 19612

How to get current timestamp in milliseconds since 1970 just the way Java gets

In Java, we can use System.currentTimeMillis() to get the current timestamp in Milliseconds since epoch time which is -

the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC.

In C++ how to get the same thing?

Currently I am using this to get the current timestamp - 

struct timeval tp;
gettimeofday(&tp, NULL);
long int ms = tp.tv_sec * 1000 + tp.tv_usec / 1000; //get current timestamp in milliseconds

cout << ms << endl;

This looks right or not?

Upvotes: 197

Views: 498280

Answers (5)

rli
rli

Reputation: 1885

If using gettimeofday you have to cast to long long otherwise you will get overflows and thus not the number of milliseconds since the epoch:

long int msint = tp.tv_sec * 1000 + tp.tv_usec / 1000;

will give you a number like 767990892 which is about 8 days after the epoch ;-).

int main(int argc, char* argv[])
{
    struct timeval tp;
    gettimeofday(&tp, NULL);
    long long mslong = (long long) tp.tv_sec * 1000L + tp.tv_usec / 1000; //get current timestamp in milliseconds
    std::cout << mslong << std::endl;
}

Upvotes: 14

Alessandro Pezzato
Alessandro Pezzato

Reputation: 8802

Since C++11 you can use std::chrono:

  • get current system time: std::chrono::system_clock::now()
  • get time since epoch: .time_since_epoch()
  • translate the underlying unit to milliseconds: duration_cast<milliseconds>(d)
  • translate std::chrono::milliseconds to integer (uint64_t to avoid overflow)
#include <chrono>
#include <cstdint>
#include <iostream>

uint64_t timeSinceEpochMillisec() {
  using namespace std::chrono;
  return duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
}

int main() {
  std::cout << timeSinceEpochMillisec() << std::endl;
  return 0;
}

Upvotes: 58

kayleeFrye_onDeck
kayleeFrye_onDeck

Reputation: 6958

This answer is pretty similar to Oz.'s, using <chrono> for C++ -- I didn't grab it from Oz. though...

I picked up the original snippet at the bottom of this page, and slightly modified it to be a complete console app. I love using this lil' ol' thing. It's fantastic if you do a lot of scripting and need a reliable tool in Windows to get the epoch in actual milliseconds without resorting to using VB, or some less modern, less reader-friendly code.

#include <chrono>
#include <iostream>

int main() {
    unsigned __int64 now = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count();
    std::cout << now << std::endl;
    return 0;
}

Upvotes: 32

Trying
Trying

Reputation: 14278

use <sys/time.h>

struct timeval tp;
gettimeofday(&tp, NULL);
long int ms = tp.tv_sec * 1000 + tp.tv_usec / 1000;

refer this.

Upvotes: 49

Oz.
Oz.

Reputation: 5458

If you have access to the C++ 11 libraries, check out the std::chrono library. You can use it to get the milliseconds since the Unix Epoch like this:

#include <chrono>

// ...

using namespace std::chrono;
milliseconds ms = duration_cast< milliseconds >(
    system_clock::now().time_since_epoch()
);

Upvotes: 357

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