CODEWITHSUNDEEP
csignalsfork
user3463055
user3463055

Reputation: 131

Catching SIGCHLD with sigaction

I am reading an article about signal and there was this part of the code which I am not sure what it is doing. Could somebody explain it for me? This article is about creating TCP un-blocked server.

struct sigaction sigchldAction;
sigchldAction.sa_handler = SIG_IGN;
sigchldAction.sa_flags = 0;
sigemptyset(&sigchldAction.sa_mask);
if (sigaction(SIGCHLD, &sigchldAction, NULL) == -1) callError("sigaction()");

Upvotes: 0

Views: 844

Answers (1)

Brian Bi
Brian Bi

Reputation: 119034

According to the Linux manual page for sigaction:

POSIX.1-1990 disallowed setting the action for SIGCHLD to SIG_IGN. POSIX.1-2001 allows this possibility, so that ignoring SIGCHLD can be used to prevent the creation of zombies (see wait(2)).

That is, explicitly ignoring SIGCHLD using SIG_IGN has the effect of causing the OS to automatically destroy child processes upon termination, so that you don't have to wait* for them. This is often what you want, although sometimes it isn't, because it also prevents the parent process from using wait* to determine the child's exit status.

Upvotes: 2

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