OK, I figured out why my original lsof experiment failed. I was using the recipe from the Perl Cookbook incorrectly. The following works as expected: 

use warnings FATAL => 'all';
no warnings 'once';
use strict;

use Parse::RecDescent;

close_all_fds();
sub close_all_fds {
  my @lsof = `/usr/bin/lsof -p $$ 2>/dev/null`;
  for my $line ( @lsof ) {
    my @flds = split ' ', $line;
    next unless $flds[ 3 ] =~ /^(\d+)/;
    my $fd = $1;
    my $fh;
    print "closing $fd\n";
    closefd( $fd );
  }
  printf Parse::RecDescent::ERROR
    "Nya, nya!  I'm still open! (BTW, I'm fileno %d)\n",
      fileno( Parse::RecDescent::ERROR );
}

use Inline C => <<EOC;
#include <unistd.h>

void closefd( int fd ) {
  if ( close( fd ) )
    Perl_croak( aTHX_ "closefd( %d ) failed", fd );
  return;
}
EOC

__END__

[download]

I still need to figure out how to selectively close those handles that correspond to STDERR and STDOUT, but with the clues++ I got from almut, I think I should be able to do it.

the lowliest monk

In reply to Re^2: How to find all open STDERR and STDOUT dups? by tlm
in thread How to find all open STDERR and STDOUT dups? by tlm

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