I need to handle SIGCHLD
properly. How can I use it with my existing code? at the moment I cant wait for the child process unless I use 0
instead of WNOHANG|WUNTRACED
.
status = 0;
pid_t child, endID;
if(amp == 1)
signal( SIGCHLD, SIG_IGN );
child = fork();
if (child < 0) {
perror("fork() error\n");
exit(EXIT_FAILURE);
} else if (child == 0) {
// do sth here
perror("error\n");
} else {
//sleep(1)
If I remove sleep
then parent is executed 1st.. why?
Here is a start (but read below):
static void
child_handler(int sig)
{
pid_t pid;
int status;
/* EEEEXTEERMINAAATE! */
while((pid = waitpid(-1, &status, WNOHANG)) > 0)
;
}
/* Establish handler. */
struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = child_handler;
sigaction(SIGCHLD, &sa, NULL);
Of course, this is all pointless. If the parent simply ignores SIGCHLD
, the children are silently reaped and won't turn into zombies.
Quoting TLPI:
Explicitly setting the disposition of SIGCHLD to SIG_IGN causes any child process that subsequently terminates to be immediately removed from the system instead of being converted into a zombie.
So something like this should do the trick for you:
signal(SIGCHLD, SIG_IGN); /* Silently (and portably) reap children. */