Std::difftime (3) Linux Manual Page

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.

std::difftime (3) Linux Manual Page