Thread: Processes / Pipes creating Son, Grandson, great-grandson

I have a proposal to create a process with pipes and i have build 20 children. It works! But the most complicated matter is to fullfil the following requirements:
I have to create a grandson for each children with pair number (c.e. 2nd, 4rth, 6th,..)and finally i have to create a great-granson for each grandson which is divisible by 6. (c.e. 6th grandson, 12th, 18th)
I'm sorry but i'm novice with unix and concurrent proceses. Here it is my simply code as basis to start.
Thanks so much!!
The code:

Code:

#include <unistd.h>
#include <sys/types.h>
main(){
pid_t pid;
int i, n=20;

for (i=0; i<n; i++) {
 pid=fork();
 if (pid == 0) break;
}
printf(“\n The father in the process %d is %d”, getpid(),getppid());
}

As you say, you have to use pipes. I can give some advice but I only learnt this two minutes ago so forgive me for any mistakes.

You need to call pipe (pipe(2) - Linux manual page) before you fork the processes. The file descriptors that you get from pipe will then be copied in to your child processes (as all data is when forked) and you can use them to communicate between processes. Simply use file writing functions like fprintf or fwrite to write data to the pipe and fscanf or fread to read data from the pipe. Best of luck.

When a child is created, all the state is the same as the parent, yes? So the child will know the value of i and can therefore create a new generation if necessary (in place of the break, perhaps).

Thenks so much i will check your recommendations. Instead i have created a simply code but i have problems with the printf..any idea where is the problem? Here i post the code:

Thanks again!!

Code:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/time.h>
#include <unistd.h>
main(){
pid_t pid;
pid_t spid;
pid_t sspid;
int i, n=20;


for (i=0; i<n; i++) {
    pid=fork();
    if (pid == 0){
        // Son process
        if(i%2 == 0){
            //Son process && even
            spid = fork();
            if (spid == 0){
                // Grand son process
                if(i%3 == 0){
                    sspid = fork();
                    if (sspid == 0){
                        // Great grand son process
                    } else {
                        // Grand son process
                    }
                }
            }
        }
        break; // to avoid continuing the for in the child processes
    } else {
        // Main process
    }
 }
 printf("The father in the process %d is %d", getpid(),getppid());
}

You'll have to be more clear what you mean about "problems with the printf".

I could guess that you mean "sometimes it prints that the parent pid is 1", and that's because if the parent process ends before the child does (and there's no reason why it shouldn't) then the child is placed under the benevolent protection of init.