On 20/02/07, Peter <[EMAIL PROTECTED]> wrote:
> Huh?? When a group leader exits his parent gets SIGCHLD. That's one of
those
> sticky PITA's of UNIX process programming. (I've just double-checked
this
> with a quick program which demonstrate it). The only way I can remember
to
> avoid receving SIGCHLD is by setting it's handler to SIG_IGN (ignore).
A correctly written pgld has no parent. When it dies its exit signal
goes to init.
Care to demonstrate? The only way I'm aware of that a process' ppid may
change is when its direct parent dies and init adopts it. I don't see any
support for your claim in the documentation I found so far. I attached my
test case at the bottom of this message.
You are getting off subject - the original question was about how to find
> out that the other side of a socketpair has closed it.
There is none. That's the point. You can monitor the pid to see if it
went away. Worse if the process becomes a zombie then even that will not
Which pid? The child may very well have forked and exited so the parent is
actually talking to its grand-children, it could also be that multiple
processes are sharing the same socketpair on the other side (that's another
contingency I'll have to take care of).
Then again - if the socketpair() is "connected" (e.g. SOCK_STREAM or
SOCK_SEQPACKET) then the kernel will notify the parent as soon as the other
side was closed. Remember we are talking about Unix domain sockets.
--Amos
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
void reaper(int signal)
{
int status;
psignal(signal, "parent: signal");
wait(&status);
printf("child terminated with exit status %d signal %d\n",
WIFEXITED(status) ? WEXITSTATUS(status) : -1,
WIFSIGNALED(status) ? WTERMSIG(status) : -1);
exit(0);
}
main ()
{
printf("parent pgrp: %d\n", getpgrp());
struct sigaction act = { .sa_handler = reaper, .sa_flags = 0, };
if (sigaction(SIGCHLD, &act, NULL) == -1) {
perror("sigaction(SIGCHLD)");
exit(1);
}
int pid = fork();
switch (pid) {
case -1:
perror("fork");
exit(1);
case 0:
if (setpgrp() < 0) {
perror("setpgrp");
exit(1);
}
printf("child pgrp: %d; ppid: %d\n", getpgrp(), getppid());
exit(0);
default:
if (setpgid(pid, pid) < 0) {
perror("parent: setpgid");
exit (1);
}
pause();
}
}
