Linuxクロック(微妙、ナノ秒)

#include 

#include 

#include 

#include 

int    time_substract(struct timeval *result, struct timeval *begin,struct timeval *end)
{

    if(begin->tv_sec > end->tv_sec)    return -1;

    if((begin->tv_sec == end->tv_sec) && (begin->tv_usec > end->tv_usec))    return -2;



    result->tv_sec    = (end->tv_sec - begin->tv_sec);

    result->tv_usec    = (end->tv_usec - begin->tv_usec);

    

    if(result->tv_usec < 0)

    {

        result->tv_sec--;

        result->tv_usec += 1000000;

    }



    return 0;

}

int main(int argc, char **argv)

{

    struct timeval start,stop,diff;



    memset(&start,0,sizeof(struct timeval));

    memset(&stop,0,sizeof(struct timeval));

    memset(&diff,0,sizeof(struct timeval));



    gettimeofday(&start,0);



    //      ...

    printf("hello world
");


    gettimeofday(&stop,0);


    time_substract(&diff,&start,&stop);

    printf("Total time : %d s,%d us
",(int)diff.tv_sec,(int)diff.tv_usec);

}

#include 
#include 
#include 

int main(void)
{
    struct timespec time_start = {0,0};
    struct timespec time_end = {0,0};

    clock_gettime(CLOCK_REALTIME, &time_start);

    printf("start time %llus, %llu ns
", time_start.tv_sec, time_start.tv_nsec);

    clock_gettime(CLOCK_REALTIME, &time_end);

    printf("end time %llus, %llu ns
", time_end.tv_sec, time_end.tv_nsec);

    return 0;
}