Fork Zombie Processes

Hello,

I have been going through stevens advanced unix programming book and have recently written a webserver. When adding forks to service incoming requests in the child and continue listening for new clients on the parent I came to a problem. Stevens says either a return from main or an exit in the child will kill the process, either that or wait() on the parent for the child. When calling exit or return from the child the processes are not being deleted but put into zombie states. Is there something I'm doing wrong? My server is long so ill give the general gist of my program.

Code:

---

int main()
{
if(fork() == 0)
{
//handle client etc etc
return 0;
}
else
{
//parent
//block on accept.
}
}

---

So I guess my question: Is return/exit not the way to ensure a child process is completely killed and not just made into a zombie? If not how can I get rid of my process without blocking on wait()?

Thanks =D

I suppose I could just handle the SIGCHLD signal and call wait in that? I dont know if that would be most efficent though?

Rather than fork()ing, try creating additional threads. Threads wont kill the process when they terminate.

Quote:

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Stevens says either a return from main or an exit in the child will kill the process, either that or wait() on the parent for the child.

---

That's incorrect.
A return from main or an exit in the child will end the child. It will remain a zombie, though.
A wait in the parent will not do anything except block the parent, if the child is running. A wait collects zombies, though.

So you need both - the child must end and the parent must wait on it to remove the zombie. To avoid being blocked in the parent, wait for SIGCHLD and do the wait in the handler.

Ahh ok thankyou very much, just making sure that was most efficient.