fork()如何返回两个值？

#include <unistd.h>
#include<stdio.h>
#include <sys/types.h>
#include <sys/wait.h>

int main() {
    pid_t pid = fork();

    if (pid < 0) {
        printf("Error: fork() failed.\n");
        return 1;
    }

    if (pid == 0) {
        printf("Child process: pid = %d, parent pid = %d\n", getpid(), getppid());
    } else {
        printf("Parent process: pid = %d, child pid = %d\n", getpid(), pid);
        wait(NULL);
    }

    return 0;
}