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

Question

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()
);

use <sys/time.h>

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

refer this.

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;
}

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;
}

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;
}