How can I handle SIGCHLD?

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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. */

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