c++ - Get millisecond part of time

Question

I need to get milliseconds from the timer

    // get timer part
    time_t timer = time(NULL);
    struct tm now = *localtime( &timer );
    char timestamp[256];

    // format date time
    strftime(timestamp, sizeof(timestamp), "%Y-%m-%d_%H.%M.%S", &now);

I want to get like this in C#:

DateTime.Now.ToString("yyyy-MM-dd_HH.mm.ss.ff")

I tried using %f or %F but it does work with C++. how can I get %f for milliseconds from tm?

Answer 1

#include <chrono>

typedef std::chrono::system_clock Clock;

auto now = Clock::now();
auto seconds = std::chrono::time_point_cast<std::chrono::seconds>(now);
auto fraction = now - seconds;
time_t cnow = Clock::to_time_t(now);

Then you can print out the time_t with seconds precision and then print whatever the fraction represents. Could be milliseconds, microseconds, or something else. To specifically get milliseconds:

auto milliseconds = std::chrono::duration_cast<std::chrono::milliseconds>(fraction);
std::cout << milliseconds.count() << '
';