Calculate diff of two struct timespec

timespec_diff.c

#include <time.h>

void timespec_diff(struct timespec *start, struct timespec *stop,
                   struct timespec *result)
{
    if ((stop->tv_nsec - start->tv_nsec) < 0) {
        result->tv_sec = stop->tv_sec - start->tv_sec - 1;
        result->tv_nsec = stop->tv_nsec - start->tv_nsec + 1000000000;
    } else {
        result->tv_sec = stop->tv_sec - start->tv_sec;
        result->tv_nsec = stop->tv_nsec - start->tv_nsec;
    }

    return;
}

<sys/time.h> has a macro for calculating the difference of two timevals called timersub.
Modifying it for timespecs is straightforward.

Thanks for that info. I just discovered that <sys/time.h> also has timespecsub() so you don't even need to modify it. It is a BSD function (actually a macro) and not a POSIX one. However, in linux we have libbsd to provide it.

The man pages includes many functions (or macros) which may also be interesting to you: man timespecsub

timerspecsub nor timersub are part of any standard.

timerspecsub nor timersub are part of any standard.

Yet they are useful, and relatively portable (Linux and BSDs).