C/C++获取时间戳和计算时间差

#include <iostream>
#include <ctime>
#include <sys/time.h>
#include <thread>         // std::this_thread::sleep_for
#include <chrono>

int main001()
{
    std::time_t t = std::time(0);  // t is an integer type
    std::cout << t << " seconds since 01-Jan-1970\n";
    return 0;
}


int main002()
{
    unsigned long int sec1 = time(NULL);
    time_t sec2 = time(NULL);  // 这里的time_t不是std:time_t
    std::cout << sec1 << std::endl;
    std::cout << sec2 << std::endl;
    return 0;
}

// C/C++获取时间戳和计算时间差
int main003()
{

    std::chrono::milliseconds ms = std::chrono::duration_cast< std::chrono::milliseconds >(std::chrono::system_clock::now().time_since_epoch());
	long start= ms.count();
	
    std::cout << ms.count() << std::endl;
	std::cout << "start="<<start << std::endl;
	
	std::this_thread::sleep_for(std::chrono::seconds(1));
	std::this_thread::sleep_for(std::chrono::milliseconds(10));
	
	ms = std::chrono::duration_cast< std::chrono::milliseconds >(std::chrono::system_clock::now().time_since_epoch());
	long end= ms.count();
	std::cout << "end="<<end << std::endl;
	
	
	std::cout << "cha="<<end-start<<" ms"<< std::endl;

    return 0;
}

struct timezone tz;
long getNowTime()
{
	struct timeval tp;
    gettimeofday(&tp, &tz);
    long int ms = tp.tv_sec * 1000 + tp.tv_usec / 1000;
	return ms;
}

int main004()
{
	long start =getNowTime();	   	
	std::cout << "start2="<<start << std::endl;
	
		
	std::this_thread::sleep_for(std::chrono::seconds(1));
	
	long end =getNowTime();	
	
	std::cout << "end2="<<end << std::endl;
	
	std::cout << "cha2="<<end-start<<" ms"<< std::endl;
	
    return 0;
}


int main()
{

    std::chrono::nanoseconds ms = std::chrono::duration_cast< std::chrono::nanoseconds >(std::chrono::system_clock::now().time_since_epoch());
	long start= ms.count();
	
    std::cout << ms.count() << std::endl;
	
	std::cout << "start="<<start << std::endl;

	std::this_thread::sleep_for(std::chrono::seconds(1));
	//std::this_thread::sleep_for(std::chrono::nanoseconds(10));
	
	ms = std::chrono::duration_cast< std::chrono::nanoseconds >(std::chrono::system_clock::now().time_since_epoch());
	long end= ms.count();
	std::cout << "end="<<end << std::endl;
	
	long cha=end-start;
	
	std::cout << "cha="<<cha/1000/1000<<" ms, cha2="<<cha/1000<<" us" << std::endl;

    return 0;
}