Question

I just tracked down a problem where I had to close all open filehandles for my Apache cgi script to continue. I traced the problem to Parse::RecDescent.

#!/usr/bin/env perl

use strict;
use warnings;
use feature qw/say/;
$|++;

print "Content-Type: text/plain\n\n";

use Parse::RecDescent;

say "$$: pre-fork: ". time;

if(my $pid = fork) {
    # parent
    say "$$: return immediately: ". time;
}
else {
    # child 
    say "$$: kicked off big process: ". time;
    close STDIN;
    close STDOUT;
    close STDERR;
    # close *{'Parse::RecDescent::ERROR'};
    sleep 5;
}

My question is how do I find all open package filehandles?

I know fileno will return a counter for an open filehandle.
Is there a way to do a reverse lookup for these, or close filehandles by their fileno counter?

Answer 1

On some systems, the directory returned by "/proc/$$/fd/" contains the list of open file descriptors. You could use POSIX::close to close them.

# close all filehandles
for (glob "/proc/$$/fd/*") { POSIX::close($1) if m{/(\d+)$}; }