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

Question

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

the difference, m

Answer 1

Include <ctime> and use the time function.

Answer 2

use <sys/time.h>

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

refer this.

Answer 3

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()
);

Answer 4

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;
}

Answer 5

If using gettimeofday you have to cast to long long otherwise you will get overflows and thus not the real 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 round 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;
}

Answer 6

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;
}