T3.c

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

void* runner(void* pid) {
    printf("My TID is: %ld\nMy PID is: %d\n", pthread_self(), *((int*) pid));
    pthread_exit(0);
}

pthread_t thread_gen(int* pid) {
    pthread_t tid;
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_create(&tid, &attr, runner, (void*) pid);
    return tid;
}

int main() {
    int cpid1, cpid2;
    switch (cpid1 = fork()) {
        case -1 :
            perror("error");
            exit(EXIT_FAILURE);
        case 0 :
            // Child process:
            pthread_t tid1, tid2;
            tid1 = thread_gen(&cpid1);
            tid2 = thread_gen(&cpid1);
            pthread_join(tid1, NULL);
            pthread_join(tid2, NULL);
            exit(0);
        default :
            // Parent process:
            int status;
            if (wait(&status) == -1) {
                perror("error");
            }
    }
    switch (cpid2 = fork()) {
        case -1 :
            perror("error");
            exit(EXIT_FAILURE);
        case 0 :
            // Child process:
            pthread_t tid1, tid2, tid3;
            tid1 = thread_gen(&cpid2);
            tid2 = thread_gen(&cpid2);
            tid3 = thread_gen(&cpid2);
            pthread_join(tid1, NULL);
            pthread_join(tid2, NULL);
            pthread_join(tid3, NULL);
            exit(0);
        default :
            // Parent process:
            int status;
            if (wait(&status) == -1) {
                perror("error");
            }
    }

    return 0;
}