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std::difftime(3)	       C++ Standard Libary		std::difftime(3)

NAME
     std::difftime - std::difftime

Synopsis
	Defined in header <ctime>
	double difftime( std::time_t time_end, std::time_t time_beg );

	Computes  difference  between  two calendar times as std::time_t objects
     (time_end -
	time_beg) in seconds. If time_end refers to time point	before	time_beg
     then the
	result is negative.

Parameters
	time_beg, time_end - times to compare

Return value
	Difference between two times in seconds.

Notes
	On  POSIX  systems,  std::time_t is measured in seconds, and difftime is
     equivalent to
	arithmetic subtraction, but C and C++ allow fractional units for time_t.

Example
     // Run this code

      #include <ctime>
      #include <iostream>

      int main()
      {
	  std::time_t start = std::time(nullptr);
	  volatile double d = 1.0;

	  // some time-consuming operation
	  for (int p = 0; p < 10000; ++p)
	      for (int q = 0; q < 100000; ++q)
		  d = d + p * d * q + d;

	  std::cout << "Wall time passed: "
		    << std::difftime(std::time(nullptr), start) << " s.\n";
      }

Possible output:
      Wall time passed: 9 s.

See also
	duration a time interval
	(C++11)  (class template)
	C documentation for
	difftime

http://cppreference.com 	   2024.06.10			std::difftime(3)

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