C++ get time in milliseconds precision

g++ -g -std=c++11 -I. h1.cpp -o h1 -luuid

#include <iostream>
#include <unistd.h>
#include <ctime>
#include <uuid/uuid.h>
#include <string>
#include <sstream>
#include <fstream>
#include <chrono>
#include <sys/time.h>

std::string getDateTime11();

int main()
{
    while(1)
    {
        cout << getDateTime11() << endl;
        sleep(1);
    }    
}

std::string getDateTime11()
{
    time_t rawtime = time(nullptr);
    struct tm timeinfo = *localtime(&rawtime);
    char *buffer = (char *)malloc(20);

    auto now = std::chrono::system_clock::now();
    auto tt = std::chrono::system_clock::to_time_t(now);
    auto nowTruncated = std::chrono::system_clock::from_time_t(tt);
    auto ms = (now - nowTruncated).count(); 
    strftime(buffer, 20, "%Y%m%d%H%M%S", &timeinfo);
    string str;
    str.append(buffer); 
    str.append(std::to_string(ms).substr(0, 3));
    return str;
}

run ./h1