#!/usr/bin/perl -w
use strict (qw(vars));

use IO::File;

our @pipes;

sub reap_pipe () {
    my ($child, $pipe) = @{ shift @pipes };
    { local ($/) = undef; $_= <$pipe>; }
    if (m/^WM_NAME: +not found/) {
    } elsif (m/^WM_NAME\(STRING\) = $/) {
    } elsif (m/^WM_NAME\(STRING\) = \"(.*)\"$/) {
	print "$child $1\n" or die $!;
    } else {
	die "$child $_ ?";
    }
    $!=0; $pipe->close(); $? and die "$? $! ?";
}

open WI, "LC_ALL=C xwininfo -root -children |" or die $!;
while (<WI>) {
    next unless m/^\s+\d+ children:/..0;
    next unless m/^\s+(0x[0-9a-f]+) /;
    my $child= $1;

    my $pipe= new IO::File "LC_ALL=C xprop -id $child WM_NAME |" or die $!;
    push @pipes, [ $child, $pipe ];

    while (@pipes > 40) { reap_pipe(); }
}
$!=0; close WI; $? and die "$? $! ?";

while (@pipes) { reap_pipe(); }

close STDOUT or die $!;