how can i avoide zombie proccess - linux

Question

I have this code:
server
while(1){ //loop the child
bzero(buffer, 256);
n = recv(newsockfd, buffer, 255,0);
printf("read %d ",n);
printf("pid %d\n",getpid());
if (n < 0) error("ERROR reading from socket");{
printf("Here is the message: %s\n", buffer);
}
if (strcmp(buffer,"quit") == 0){
printf("Disconnect from %s:%d\n",str,portno);
exit(EXIT_SUCCESS);
}else{
n = send(newsockfd, "message received\n", 19,0);
if (n < 0) error("ERROR writing to socket");
bzero(buffer, 256);
}
}
}else{ //parent
recv(newsockfd,gepid,10,0); //get the child pid
endID = waitpid(gepid,&status,WNOHANG|WUNTRACED); //get the exit code gepid want to be the child pid
if (endID==-1){
error("waitpid");
}else if (endID==0){
printf("Child still running!");
}else if(endID==childpid){
check_child_exit(status);
}
}
}
close(newsockfd);
return 0;
}
client
while(1){ //while after connect
printf(inet_ntoa(serv_addr.sin_addr));
printf(" :>");
bzero(buffer, 256);
printf("pid: %d",&getpid);
//fgets(buffer,255,stdin);
scanf("%s",&buffer[0]);
if ( send(sockfd, buffer, strlen(buffer),0)< 0)
error("ERROR writing to socket");
if(strcmp(buffer,"quit") == 0){
close(sockfd);
printf("Client: %s Disconnect \n",inet_ntoa(serv_addr.sin_addr));
gepid[0]=getpid(); //there is the error i want to get the pid of child
send(sockfd,gepid,10,0); //and send to server
exit(1);
}
if (recv(sockfd, buffer, 255,0)< 0){
error("ERROR reading from socket");
}else{
printf("%s\n %d", buffer,n);
}
}
return 0;
}
I have a server that can serve multy client and response to each one when the client write quit or stop with a signal[CTR-C] i want the server get that and avoid zombie proccess so to avoid zombie proccess i thought
to send from client to server the getpid so the client get the pid of the kid proccess when the proccess finish with quit or stop by signal parent get the exit with waitpaid
so the programm not have zombie proccess i dont know if this logic is good to stop the zombie proccess but i try to send pid from client to server and i get segmentation fault
Any help is appreciate

Answer 1

There are numerous problems with your code, but to focus on your question:
Don't try sending the pid to the server. It's unnecessary, and wouldn't work if the child crashes before it can send it anyway.
The usual way is to catch the SIGCHLD signal, and do any necessary waitpid stuff from inside the signal handler. But if your only concern is avoiding zombies, then just install a default signal handler with signal(SIGCHLD, SIG_IGN);, and don't use waitpid at all.

Answer 2

fork() returns 0 in the child and the child pid in the parent, so there is no need to send pid from child to parent. If you are forking multiple times, then you need to store each child pid for collection later.
You are not showing the type of gepid. Is it pid_t gepid2 or something? The len parameter to recv() is in bytes, so it would be more appropriate to recv(sock, gepid, sizeof(gepid[0]), 0);
Also if you pass -1 to waitpid(), it waits for any child.