std::difftime

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

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

#include <iostream>
#include <ctime>
 
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";
}

Wall time passed: 9 s.

See also