std:: difftime

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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

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