parent and child processes

skora · 11-01-2003, 09:09 PM

I have a problem to make a program that is going to create n processes.
The first process, which is initial program, creates the second process, which in turn creates the third process, and so on until the nth process is created.
my code so far looks like this and when i run it some child processes create more then one child process (every process should create only one child!)
any suggestions how to fix this?

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <iostream.h>


static int n;
void makeprocess();

int main (int argc, char *argv[])
{

        if (argc != 2) {
                printf ("Usage: %s <#processes>\n", argv[0]);
                      exit (1);
           }

           n = atoi (argv[1]);
           if (n > 10 && n < 1)  // create up to 10 new processes
           {
                       printf ("Wrong number of processes (> 10)\n");
                       exit (1);
           }        
         if (fork() == -1)  {        // create 1st process
                       perror ("fork");
                      exit (1);
          }
        n--;

        printf("n:%d  process ID:%d  parent ID:%d\n",
          n, getpid(), getppid());

           makeprocess();


   return 0;
}

void makeprocess()
{
   n--;
        cout <<"n "<<n<<endl;
   if (fork() == -1)  {
        perror ("fork");
        exit (1);
    }
   printf("n:%d  process ID:%d  parent ID:%d\n",
          n, getpid(), getppid());

    if (n > 0) {
        makeprocess();
        }
 
}

SaTaN · 11-01-2003, 09:50 PM

Quote:

The first process, which is initial program, creates the second process, which in turn creates the third process, and so on until the nth process is created

I don't think that is what is going to happen.It will be more like a binary tree i.e, the parent will be producing another child also .

Code:

                                           PARENT
                      PARENT                          PARENT_CHILD1
             PARENT       PARENT_CHILD2       PARENT_CHILD1   PARENT_CHILD1_CHILD

I suppose,
You will have to stop any process from creating more than one process to implement that

skora · 11-01-2003, 10:11 PM

Quote:

Originally posted by SaTaN
I don't think that is what is going to happen.It will be more like a binary tree i.e, the parent will be producing another child also .

Code:

PARENT PARENT PARENT_CHILD1 PARENT PARENT_CHILD2 PARENT_CHILD1 PARENT_CHILD1_CHILD

I suppose,
You will have to stop any process from creating more than one process to implement that

you are right (that is what happened after i run my code).
But the thing is i have to make it so it every parent creates only one child and its child creates only one child an so on... so my question is do you know how i can fix my code so i can get structure like this

Code:

                                           PARENT
                      PARENT                          CHILD1
                      CHILD1                           CHILD2  
                      CHILD2                           CHILD3
                      CHILD3                           CHILD4
...........
.                     CHILDn -1                       CHILDn

champ · 11-01-2003, 11:15 PM

posted twice: look at the next one

champ · 11-01-2003, 11:22 PM

you will have to check the return value of the fork() call.
In the parent process, fork() will return the pid of the child, while the fork() returns 0 in the child process.

So if you don't want both processes to create a new process you will have to do something like this.

Code:

// in makeprocess()

pid_t pid;
pid = fork();

switch (pid)
{
 case -1:
      perror ("fork");
      exit (1);
 case 0:
      makeProcess();
}

This way only the child will create a new process.

skora · 11-02-2003, 10:41 AM

thank you guys
i fixed my code...