NAME¶

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