without Windows OS

#include <time.h>
/*
   struct timespec {
      time_t   tv_sec;        // seconds
      long     tv_nsec;       // nanoseconds
   };
 */

main()
{
   struct timespec tp;
   int rs;

   rs = clock_gettime(CLOCK_REALTIME, &tp);
   printf("%ld %ld\n", tp.tv_sec, tp.tv_nsec);
   rs = clock_gettime(CLOCK_REALTIME, &tp);
   printf("%ld %ld\n", tp.tv_sec, tp.tv_nsec);
   return 0;
}

$ gcc -o test test.c -lrt

http://kldp.org/node/56996