clk_test.c

#include <time.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

int main(int argc, char *argv[])
{
    struct timespec         cur;
    struct timespec         prev;
    unsigned int            ticks;
    int                     delay;

    if(argc > 1)
    {
        delay = atoi(argv[1]);
    }
    else
    {
        delay = 1;
    }

    printf("Using delay=%u milliseconds between calls.\n", delay);

    if(clock_getres(CLOCK_MONOTONIC_RAW, &cur) != 0)
    {
        printf("Failed clock resolution read errno=%d [%s].\n",
                errno, strerror(errno));
        return(0);
    }

    printf("Clock resolution sec=%lu nsec=%lu\n",
            cur.tv_sec, cur.tv_nsec);

    if(clock_gettime(CLOCK_MONOTONIC_RAW, &cur) != 0)
    {
        printf("Failed initial read errno=%d [%s].\n",
                errno, strerror(errno));
        return(0);
    }

    printf("Initial time sec=%lu nsec=%lu\n",
            cur.tv_sec, cur.tv_nsec);

    ticks = 0;

    while(1)
    {
        prev = cur;

        poll(0, 0, delay);

        if(clock_gettime(CLOCK_MONOTONIC_RAW, &cur) != 0)
        {
            printf("Failed subsequent read errno=%d [%s].\n",
                    errno, strerror(errno));
            return(0);
        }

        if((cur.tv_sec <= prev.tv_sec) &&
                (cur.tv_nsec < prev.tv_nsec))
        {
            printf("Time ran backward:\n\tcur:\t%lu %lu\n\tprev:\t%lu %lu\nInterval is >= %u milliseconds).\n",
                    cur.tv_sec, cur.tv_nsec,
                    prev.tv_sec, prev.tv_nsec,
                    delay);
        }

    }

    return(0);
}