std::difftime (3) - Linux Manuals

std::difftime: std::difftime

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 <iostream>
  #include <ctime>

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

      // some time-consuming operation
      for (int n=0; n<10000; ++n) {
          for (int m=0; m<100000; ++m) {
             d += d*n*m;
          }
      }

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

Output:

  Wall time passed: 7 s.