Child creates another child that creates another child... and so on[How to?]

[pfpietro]

Hi guys,

I'm writing a program where I have to give in the command line an integer that define the number of consecutive children. For exemple, if the number is 3, the first child will create a second child that will create a third child.

I have no idea how to do it on C# since the number of consecutive children is a number passed by the user ( the value on argv[1] when the prog is called. ex.: ./program 3 )

Also how to handle the wait of the respective father.

could someone give me a hand ?

[]'s

[Veltas]

What do you mean by children?

Also, is this actually a C++ question? This is a C++ forum.

[pfpietro]

Yep, C or C++, I think there's no difference.

By child I mean when you create a process through the command "fork()".

Am I in the wrong forum ?

[BlackSheep]

There is a difference between C and C++. C++ is (almost) a superset of C. And C# is something entirely different.

And your question:

int num; //Your number of children
while(fork() == 0 && --num >= 0) ;

EDIT: Note that there is no error checking, so if you create less children then no one will know. Also, you'll probably want to save the PID of the children.

[pfpietro]

BlackSheep, thank you man. I'm working with C ( not c#, sorry about that ).

But since I'm still a noob in C, could you explain me that while ?

While fork()==0 and --num >=0 ?

what is the --num ? I tought the --variable was only to decrease a variable, not to use in a declaration like that...

and I did't understand the while fork()==0 statement...

Inside that while I should put something like

pid[num]=fork();
--num 

???
and what about the wait() ??

[BlackSheep]

'--' is predecrement. It subtracts one from num before comparing it to 0 (If you didn't know this I'm not sure why you're working with fork.)
Num is declared before the while loop.

You can put it all in the while statement:

int num; //Your number of processes
PID child; //This process's child's PID
while((PID = fork()) == 0 && --num > 0);

fork() creates a perfect copy of the current process, with the only difference being the return value. 0 for children, and the PID of the child for parents.

Synching your processes will be a lot harder. You'll need to use something like shared memory ( http://www.cs.cf.ac.uk/Dave/C/node27.html ), or sockets to have the processes communicate.