让流程等待它的“兄弟”流程

Question

I'm trying to create a full tree of processes without killing the parents / child.

SO far I could only create one side of the tree, then It kills all the process (bottom to top) then I create the other side of the tree.

What do I need to do to create the whole tree before the processes ends and dies ?

My code creating each side at a time###

 #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

I need to do something like this:

What is happening with my currently code:

P1 -> P2 -> P4 -> Kill P4 -> P5 -> KILL P5 -> KILL P2
P3 -> P6 -> KILL P6 -> P7 -> KILL P7 -> KILL P3 -> KILL P1

I need to let them all 'alive' at same time, jusst then I kill them all.

Answer 1

You can use signal. You have to save the id of P4 and after P4 executes the printf you call pause() . Then do it for P5 and P6. When you create the last one, in this case the P7, the tree is completed and you send a signal to the process that was paused using kill() , making them end the execution.