Hi everyone,

I'm trying to accomplish the following; I need to create 2 subprocesses and each subprocess should create a process of their own.

Should look like this:

I'm child xxxx parent xxxx
I'm the subchild xxxx parent xxxx
I'm the second child xxxx parent xxxx
I'm the second subchild xxxx parent xxxx

So far I have this

#include <stdio.h>

int main()
{
    int pid;
    pid = fork();
    if (pid) {
	printf("I'm the parent %d\n", getpid());
    } else {
        printf("I'm the child %d parent %d\n", getpid(), getppid());
	pid = fork();
	if (pid) {

        } else {
		printf("I'm the subchild %d parent %d\n", getpid(), getppid());
        }
    }
    return 0;
}

The above creates a child process and another process but for some reason it does not get the PPID from the child it's been created from. I wonder why is this.

The current output looks like:

I'm the parent 6213
I'm the child 6214 parent 6213
I'm the subchild 6215 parent 1

The subchild's parent should be 6214. Some help would be greatly appreciated

Edited 6 Years Ago by MrDiaz: n/a

Notice parent 1 . Process with pid 1, aka init, besides other things, adopts every orphan. This means that by the time 6215 prints its message, 6214 is already dead.

Edited 6 Years Ago by nezachem: n/a

Yes I noticed that from the output, and so would any process derived from there as well. How can I fix this?

You have to make the parent wait for the child to die before killing itself. A simple solution will be to use wait(NULL) in the parent

Now the parent waits for the child to die before terminating

int main()
{
    int pid;
    pid = fork();
    if (pid)
    {
                printf("I'm the parent %d\n", getpid());
                wait(NULL);
                printf("The child has died\n");
    }
    else
    {
                printf("I am the child\n");
    }
    return 0;
}

You have to make the parent wait for the child to die before killing itself. A simple solution will be to use wait(NULL) in the parent

Now the parent waits for the child to die before terminating

int main()
{
    int pid;
    pid = fork();
    if (pid)
    {
                printf("I'm the parent %d\n", getpid());
                wait(NULL);
                printf("The child has died\n");
    }
    else
    {
                printf("I am the child\n");
    }
    return 0;
}

Yeah! i was to reply the same...

Very good answer....

Yeah that's interesting, I also did it some other way which basically does what I want but only creates one child and a subchild. I need a second child and a subchild for this second child.

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

int main(void) {
	int pid;
	pid = fork();
	if (pid == 0) { // Child process
		printf("I'm the child %d parent %d\n", getpid(), getppid());
		pid = fork();
		if (pid == 0) { // Subchild process
			printf("I'm the subchild %d parent %d\n", getpid(), getppid());
		}
	}
	wait();
	return 0;
}

I'm trying to start a new process but I'm stuck there, it does the whole thing twice and output isn't right

When you fork for the second time, the parent is not waiting. Also only the parent should wait (See my example above)

Just finished the code, got it working the way I wanted to. Take a look and now maybe it will make sense what I was trying to do

#include <stdio.h>

int main(void) {

	int pID;

	pID = fork();
	if (pID == 0) { // First Child Process
		printf("I am the child %d parent %d\n", getpid(), getppid());
		
		pID = fork();
		if (pID == 0)
			printf("I am the subchild %d parent %d\n", getpid(), getppid());
	}
	else {
		pID = fork();
		if (pID == 0) { // Second Child Process
			printf("I am the second child %d parent %d\n", getpid(), getppid());
		pID = fork();
		if(pID == 0)
			printf("I am the second subchild %d parent %d\n", getpid(), getppid());
		}
	}	
	return 0;
}
This question has already been answered. Start a new discussion instead.