Я попробовал
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
int main(void) {
printf("master process is %d.\n", getpid());
fork();
fork();
fork();
wait(0);
printf("my pid is %d; my parent pid is %d\n", getpid(), getppid());
return 0;
}
и получил вывод
master process is 28982.
my pid is 28982; my parent pid is 31294
my pid is 28985; my parent pid is 28982
my pid is 28984; my parent pid is 28982
my pid is 28983; my parent pid is 1
my pid is 28986; my parent pid is 28984
my pid is 28988; my parent pid is 28983
my pid is 28987; my parent pid is 1
my pid is 28989; my parent pid is 28987