std::difftime

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< cpplrm; | chronolrm; | c
Date and time utilities
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Clocks
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Calendars
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Time zones
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C-style date and time
C-style date and time utilities
Functions
Time manipulation
difftime
Format conversions
Constants
Types
(C++17)
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

#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.

See also

(C++11)
a time interval
(class template)