std::chrono::file_clock::now (3) - Linux Manuals

std::chrono::file_clock::now: std::chrono::file_clock::now

NAME

std::chrono::file_clock::now - std::chrono::file_clock::now

Synopsis

static std::chrono::time_point<std::chrono::file_clock> now() noexcept; (since C++20)

Returns a time point representing the current point in time.

Parameters

(none)

Return value

A time point representing the current time.

Example

// Run this code

  #include <iostream>
  #include <vector>
  #include <numeric>
  #include <chrono>

  volatile int sink;
  int main()
  {
      for (auto size = 1ull; size < 1000000000ull; size *= 100) {
          // record start time
          auto start = std::chrono::file_clock::now();
          // do some work
          std::vector<int> v(size, 42);
          sink = std::accumulate(v.begin(), v.end(), 0u); // make sure it's a side effect
          // record end time
          auto end = std::chrono::file_clock::now();
          std::chrono::duration<double> diff = end-start;
          std::cout << "Time to fill and iterate a vector of "
                    << size << " ints : " << diff.count() << " s\n";
      }
  }

Possible output:

  Time to fill and iterate a vector of 1 ints : 2.43e-07 s
  Time to fill and iterate a vector of 100 ints : 4.1e-07 s
  Time to fill and iterate a vector of 10000 ints : 2.519e-05 s
  Time to fill and iterate a vector of 1000000 ints : 0.00207669 s
  Time to fill and iterate a vector of 100000000 ints : 0.423087 s