Mencoba membuat 2 proses anak dan 1 cucu yang berjalan secara berurutan

Jadi saya mencoba membuat 2 proses anak dan satu proses cucu dari anak pertama. Saya mencoba menjalankan proses anak pertama, lalu cucu, lalu anak kedua dengan orang tua memanggil pid ketika proses selesai. Saya benar-benar buntu - Saya memiliki banyak versi kode dari kode tersebut tetapi tidak dapat mengaktifkannya dalam urutan yang benar. Bantuan, saran, atau tautan apa pun akan sangat dihargai.

Output yang diinginkan adalah

-Saya anak pertama

----Akulah cucunya

Saya orang tuanya, anak pertama memiliki pid 21505

-Saya anak pertama, cucu punya pid 21506

-Coba lagi

--Saya anak kedua

-- -->Anak kedua: 1317 byte ditransfer.

Saya orang tuanya lagi, anak kedua punya pid 21507

Induk - Anak 21507 selesai

-Coba lagi

**** akan melihat 20 baris pertama file lab4.c di sini

Induk - Anak lainnya 21505 selesai

int main(int* argc, char* args[])
{
pid_t child1, child2, gchild; //process ids
child1 = fork();           //Create the two child processes
if (child1 == 0)
{ // parent
    child2 = fork();
    if (child2 == 0)
    { //parent
        printf("P: first child has pid %d\n", child1);
        printf("P: second child has pid %d\n", child2);

        pid_t wpid; // process id that is finished
        int status; //status code returned by process  
                    //Wait for all child processes to complete
        while ((wpid = wait(&status)) > 0)
        {
            if (wpid > 0)
            {
                printf("P: Child %d is done \n", wpid);
            }
        };

        exit(0); //exit main parent process
    }
    else
    {
        //Second process's code

        printf("SC: I am the second child.\n");
        int totalBytes = 0; //total number of bytes in the file we are going to read in
        char buffer[2056]; //file contents size 2056 bytes
        ssize_t read_bytes = 0; //Bytes from each chunk get placed here temporarily

        ///Read in file contents: home/common/lab_sourcefile
        int fd_in = open("/home/COIS/3380/lab4_sourcefile", O_RDONLY);//open the file
        do
        {
            //read the file chunk by chunk to the buffer
            read_bytes = read(fd_in, buffer, (size_t)2056);

            // End of file or error.
            if (read_bytes <= 0)
            {
                break; //done reading file
            }

            //Save the total number of bytes
            totalBytes = totalBytes + read_bytes;
        } while (1); //infinite loop until we are done reading the file

        //Write out contents to: lab4_file_copy
        char filepath[1024]; //temp path
        getcwd(filepath, sizeof(filepath)); //Get the current working directory
        strcat(filepath, "/lab4_file_copy"); //Tack on the filename
        int fd = open(filepath, O_RDWR | O_CREAT, S_IRUSR | S_IRGRP | S_IROTH); //open the file. O_RDWR = read and write flag, O_CREAT = create if doesnt exist, S_* flags are permission flags from fstat 
        write(fd, buffer, strlen(buffer)); //write to the file

        close(fd_in);//close file we were reading
        close(fd); //close copy file

        // print out the number of bytes the file
        printf("SC: --> Second child: %d bytes transferred.\n", totalBytes);

        exit(0); //done kill second child process
    }
}
else
{
    //First child process

    printf("FC: I'm the first child.\n");

    //Create the granchild process
    gchild = fork();
    if (gchild == 0)
    {
        printf("GC: I am the grandchild.\n");

        sleep(3); //sleep for 3 seconds

        printf("GC: #### Output start ####\n");
        execlp("head", "head", "-n", "20", "l.c", NULL); //this should exit automatically
        printf("ERROR: execlp command failed\n");//This will only run if the execlp process fails
        exit(1); //FAILED!
    }
    else
    {
        //Output the granchild pid
        printf("FC: I am the first child, grandchild has pid %d\n", gchild);
        int grandchildStatus;
        //Wait for grandchild process to be done. Polling...
        while ((waitpid(gchild, &grandchildStatus, WNOHANG)) != gchild)
        {
            printf("FC: Try again\n");
            sleep(1);
        };
        printf("GC: #### Output end ####\n");
        //End of first child. Grandchild must have completed.

        exit(0); //Done. kill first child process
    }
}

}