Re: $SIG{INT} unlink problem

I think the answer by sauoq will most likely be the right one.

I just wanted to chime in with something else. Your code is assuming that fork() always succeeds (a dangerous assumption). Remember that it will return undef upon failure. A failure can be triggered by many events outside of your control, so you should be prepared to deal with them gracefully.

I offer you this substitute code instead:

use strict;
use warnings;

use constant FORK_WAIT => 2;
use constant MAX_ATTEMPTS => 10;
our $attempt = 0;

my $pid = undef;

while (not defined ($pid = fork())) {
    die "Too many failed fork() attempts: $!\n"
        if ++$attempt > MAX_ATTEMPTS;
    warn "fork() failed: $!\n";
    sleep $FORK_WAIT;
}

if ($pid) {

# I'm the father

} else {

# I'm the son

}
[download]

Hope this helps,

Edit: Thanks to wtp for the correction in the Perl's fork() behavior.

Comment on Re: $SIG{INT} unlink problem Download Code

Replies are listed 'Best First'.
Re: Re: $SIG{INT} unlink problem by wtp (Initiate) on Aug 21, 2002 at 15:51 UTC
Oh, if only it were so! The Perl version of fork returns undef on failure. my $pid; until ( defined ($pid = fork)) { ...	[reply]
Re: Re: $SIG{INT} unlink problem by agentv (Friar) on Aug 22, 2002 at 02:15 UTC
When I saw this, I knew that I had seen what ballplayers call "a thing of beauty." `while (not defined ($pid = fork())) { die "Too many failed fork() attempts: $!\n" if ++$attempt > MAX_ATTEMPTS; warn "fork() failed: $!\n"; sleep $FORK_WAIT; }` [download] Every artifice that is used here is in its finest form and in proper proportion. And I must know fokat, did your posting originally say that fork() returns -1 on failure? (That is the SVR4 behavior for the system call I believe, and until last week, I had forgotten totally about this as well as the original author of this thread. "Oh," I said, "of course fork can fail! Let's do check for that." While secretly he thinks, Damn, I wonder how much code I should revisit to account for this.) ...All the world looks like -well- all the world, when your hammer is Perl. ---v	[reply] [d/l]