How to make a process wait for 'brothers'

Question

Hello. I need to create a process tree, until the moment what I was able to do was create a side of the tree, kill everything and then create the other side.
But I need to raise the whole tree first and start killing the children and the father.

My code that creates a side -> kills everything -> creates the other -> kills everything -> kills the father. I’ve tried using wait(), waitpid() and I can’t get P4 to wait for P5 and both wait for P6 and P7

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

int main(){
    clock_t t;
    double time_taken;
    t = clock();
    int status;
    pid_t idProcesso; // P1
    printf("I'm P1: %d  |  my dad: %d\n", getpid(), getppid());
    idProcesso = fork();    

    switch(idProcesso){
        case -1: exit(-1); //ERROR
        case 0: //P2
            printf("I'm P2: %d  |  my dad P1: %d\n", getpid(), getppid());          
            idProcesso = fork();
            switch(idProcesso){
                case -1: exit(-1); //Error
                case 0: //P4
                    printf("I'm P4: %d  |  my dad P2: %d\n", getpid(), getppid());
                    break;

                default: //Continue P2
                wait(&status);
                printf("I'm P2: %d  |  Already waited for my son P4: %d\n", getpid(), idProcesso);
                idProcesso = fork(); //P5
                switch(idProcesso){
                    case -1: exit(-1); //ERROR
                    case 0: //P5
                        printf("I'm P5: %d  |  my dad P2: %d\n", getpid(), getppid());
                        break;
                    default: //Continue P5
                        wait(&status); //P2 waits his son P5
                        printf("I'm P2: %d  |  Already waited for my son P5: %d\n", getpid(), idProcesso);
                        break;

                }
            }
        break;
        default: //Continue P1          
            wait(&status);
            printf("I'm P1: %d  |  Already waited for my son P2: %d\n", getpid(), idProcesso);
            idProcesso = fork(); //P1 creates son
            switch(idProcesso){
                case -1: exit(-1); //ERROR
                case 0://P3
                    printf("I'm P3: %d  |  my dad P1: %d\n", getpid(), getppid());
                    idProcesso = fork(); //P3 creates son P6
                    switch(idProcesso){
                        case -1: exit(-1); //ERROR
                        case 0: //P6 son of P3
                            printf("I'm P6: %d  |  my dad P3: %d\n", getpid(), getppid());
                            break;
                        default: //Continue P3
                            wait(&status); //P3 waits his son P6
                            printf("I'm P3: %d  | Already waited for my son P6: %d\n", getpid(), idProcesso);
                            idProcesso = fork(); //P3 creates son P7
                            switch(idProcesso){
                                case -1: exit(-1);//ERROR
                                case 0: //P7 son of P3
                                    printf("I'm P7: %d  |  son of P3: %d\n", getpid(), getppid());
                                    break;
                                default: //P3 waits son P7
                                    wait(&status);
                                    printf("I'm P3: %d  |  Already waited for my son P7: %d\n", getpid(), idProcesso);
                                    break;
                            }
                            break;
                    }
                    break;                  
                default: //Continue P1              
                    wait(&status); // P1 waits his son P3
                    printf("I'm P1 again, my id: %d\n", getpid());
                    t = clock() - t;
                    time_taken = ( (double)t ) / CLOCKS_PER_SEC;
                    printf("Time used in seconds: %f\n", time_taken);
            }
            break;
    } //SWITCH
} //Main  

What I need to do:

Answer 1

The problem is that you are putting the commands of wait() before the commands of fork() creating the next processes. For example, in P2, before executing the wait() what hopes P4 you must perform the fork() creating P5. Likewise, in P1, before executing the wait() P2 waiting you must perform the fork() that creates P3.

The code would look something like this:

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

int main(){
    clock_t t;
    double time_taken;
    t = clock();
    int status;
    pid_t idProcesso; // P1
    pid_t idChild; // Aby child process
    printf("I'm P1: %d  |  my dad: %d\n", getpid(), getppid());
    idProcesso = fork();    

    switch(idProcesso){
        case -1: exit(-1); //ERROR
        case 0: //P2
            printf("I'm P2: %d  |  my dad P1: %d\n", getpid(), getppid());          
            idProcesso = fork();
            switch(idProcesso){
                case -1: exit(-1); //Error
                case 0: //P4
                    printf("I'm P4: %d  |  my dad P2: %d\n", getpid(), getppid());
                    sleep(5);
                    break;

                default: //Continue P2
                idProcesso = fork(); //P5
                switch(idProcesso){
                    case -1: exit(-1); //ERROR
                    case 0: //P5
                        printf("I'm P5: %d  |  my dad P2: %d\n", getpid(), getppid());
                        sleep(5);
                        break;
                    default: //Continue P5
                        idChild = wait(&status);
                        printf("I'm P2: %d  |  Already waited for my son: %d\n", getpid(), idChild);
                        idChild = wait(&status); //P2 waits his son P5
                        printf("I'm P2: %d  |  Already waited for my son: %d\n", getpid(), idChild);
                        break;

                }
            }
        break;
        default: //Continue P1
            idProcesso = fork(); //P1 creates son
            switch(idProcesso){
                case -1: exit(-1); //ERROR
                case 0://P3
                    printf("I'm P3: %d  |  my dad P1: %d\n", getpid(), getppid());
                    idProcesso = fork(); //P3 creates son P6
                    switch(idProcesso){
                        case -1: exit(-1); //ERROR
                        case 0: //P6 son of P3
                            printf("I'm P6: %d  |  my dad P3: %d\n", getpid(), getppid());
                            sleep(5);
                            break;
                        default: //Continue P3
                            idProcesso = fork(); //P3 creates son P7
                            switch(idProcesso){
                                case -1: exit(-1);//ERROR
                                case 0: //P7 son of P3
                                    printf("I'm P7: %d  |  son of P3: %d\n", getpid(), getppid());
                                    sleep(5);
                                    break;
                                default: //P3 waits son P7
                                    idChild = wait(&status); //P3 waits his son P6
                                    printf("I'm P3: %d  | Already waited for my son: %d\n", getpid(), idChild);
                                    idChild = wait(&status);
                                    printf("I'm P3: %d  |  Already waited for my son: %d\n", getpid(), idChild);
                                    break;
                            }
                            break;
                    }
                    break;                  
                default: //Continue P1
                    idChild = wait(&status);
                    printf("I'm P1: %d  |  Already waited for my son: %d\n", getpid(), idChild);
                    idChild = wait(&status); // P1 waits his son P3
                    printf("I'm P1: %d  |  Already waited for my son: %d\n", getpid(), idChild);
                    printf("I'm P1 again, my id: %d\n", getpid());
                    t = clock() - t;
                    time_taken = ( (double)t ) / CLOCKS_PER_SEC;
                    printf("Time used in seconds: %f\n", time_taken);
            }
            break;
    } //SWITCH
} //Main

Note that this solution ensures that no process will wait for another to be created. However, it does not guarantee that the entire tree will be created before the processes are finished. If the P4 process, for example, finishes very fast, it may be that there has been no time for the P7 process to be created yet.

To illustrate a more realistic case, where sheet processes perform a longer operation than a simple break(), I introduced the sleep(5) at the end of each process. If you delete it, you may notice cases where some processes end before others have been created.