std::difftime

 

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C-style date and time

 

C-style date and time utilities

Functions

Time manipulation

difftime

time

clock

timespec_get (C++17)

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asctime

ctime

strftime

wcsftime

gmtime

localtime

mktime

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CLOCKS_PER_SEC

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tm

time_t

clock_t

timespec (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

Run this code

#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";
}

Possible output:

Wall time passed: 9 s.

See also

duration (C++11)

a time interval (class template)