summer.cpp

#include <chrono>
#include <cstdlib>
#include <iostream>
#include <signal.h>
#include <string>
#include <unistd.h>

volatile double sum = 0;
std::chrono::system_clock::time_point start_time;

void sig_handler(int s)
{
  auto end = std::chrono::system_clock::now();
  std::chrono::duration<double> diff = end - start_time;
  std::cout << diff.count() << "s elapsed" << std::endl;
  std::cout << sum << std::endl;
}

int
main(int argc, char *argv[])
{
  if (argc < 2)
  {
    std::cout << "Gimme a number! (up to size ull)" << std::endl;
    exit(1);
  }

  unsigned long long number = atoll(argv[1]);
  signal(SIGUSR1, sig_handler);

  std::cout << "Send SIGUSR1 to this process to print the time elapsed and ";
  std::cout << "current sum" << std::endl;
  std::cout << "PID: " << ::getpid() << std::endl;
  std::cout << "Ready!" << std::endl;
  start_time = std::chrono::system_clock::now();
  for (unsigned long long i = 1; i < number; ++i)
  {
    sum += 1.0 / i;
  }
  auto end_time = std::chrono::system_clock::now();
  auto diff = end_time - start_time;
  std::cout << "Finished in " << diff.count() << "s" << std::endl;
  std::cout << sum << std::endl;

  exit(0);
}