$ cat fork.c
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

void print_time(const char *pfx)
{
        struct timespec ts;
        clock_gettime(CLOCK_MONOTONIC, &ts);
        fprintf(stderr, "%s: %lld.%09lld\n", pfx,
            (long long)ts.tv_sec, (long long)ts.tv_nsec);
}

int main(void)
{
        print_time("parent");
        pid_t p = fork();

        if (p == 0) {
                print_time("child");
                exit(0);
        } else {
                wait(NULL);
                print_time("terminate");
        }
        return 0;
}

$ cc -O2 fork.c
$ time for i in `seq 1 10`; do echo $i; ./a.out; done
1
parent: 4398686.537642541
child: 4398686.537748040
terminate: 4398686.537958548
2
parent: 4398686.538785531
child: 4398686.538892553
terminate: 4398686.539060510
3
parent: 4398686.539724745
child: 4398686.539823872
terminate: 4398686.539950241
4
parent: 4398686.540690420
child: 4398686.540785870
terminate: 4398686.540900056
5
parent: 4398686.541547419
child: 4398686.541640665
terminate: 4398686.541757005
6
parent: 4398686.542347922
child: 4398686.542433363
terminate: 4398686.542533983
7
parent: 4398686.543091006
child: 4398686.543175445
terminate: 4398686.543264173
8
parent: 4398686.543787081
child: 4398686.543862984
terminate: 4398686.543979855
9
parent: 4398686.544548029
child: 4398686.544645603
terminate: 4398686.544757895
10
parent: 4398686.545287246
child: 4398686.545375623
terminate: 4398686.545507502

real    0m0.010s
user    0m0.004s
sys     0m0.006s