threads and fork example

fork.c

#include <stdio.h>

int id;

int main() {
    id = fork();
    if (id == 0) {
        printf("Child : Child ID: %d, Parent ID: %d\n", getpid(), getppid());
    }
    else {
        printf("Parent : ID: %d, Child ID: %d\n", getpid(),id);
    }
    return 0;
}

forkWithPipe.c

#include<stdio.h>
#include <pthread.h>
#include <unistd.h>

int tmp1, tmp2, fileDescriptor[2];
char readBuffer[80], messageChild[] = "child";

int main() {
    pipe(fileDescriptor);
    tmp1 = fork();
    if (tmp1 == 0) {
        close(fileDescriptor[0]);
        write(fileDescriptor[1], messageChild, sizeof(messageChild));
    }
    else if (tmp1 > 0) {
        close(fileDescriptor[1]);
        read(fileDescriptor[0], readBuffer, sizeof(readBuffer));
        printf("c1 : %s\n", readBuffer);
    }
    tmp2 = fork();

    if (tmp2 == 0) {
        close(fileDescriptor[1]);
        read(fileDescriptor[0], readBuffer, sizeof(readBuffer));
        printf("c2 : %s\n", readBuffer);
    }else if (tmp2 > 0) {
        close(fileDescriptor[0]);
        write(fileDescriptor[1], messageChild, sizeof(messageChild));
    }
    return 0;
}

thread.cpp

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>

pthread_t tid[2];
int fileDescriptor[2],i;
char message[] = "received", readBuffer[80];

void *function(void *args) {
    if (pthread_equal(pthread_self(), tid[0])) {
        if (fork() == 0) {
            close(fileDescriptor[0]);
            write(fileDescriptor[1], message, sizeof(message));
        }
    } else {
        if (fork() == 0) {
            close(fileDescriptor[1]);
            read(fileDescriptor[0], readBuffer, sizeof(readBuffer));
            printf("%s\n", readBuffer);
        }
    }
    sleep(10);
    return NULL;
}

int main() {
    pipe(fileDescriptor);
    for(i = 0 ; i < 2 ; i++){
        if (pthread_create(&(tid[i]), NULL, &function, NULL) != 0) {
            printf("failed\n");
        }
        else {
            printf("created\n");
        }
    }
    sleep(10);
    return 0;
}