$hl->{$_}->{retry} = 0;
	$hl->{$_}->{retries} = 0;

	my $start = time;
	my $blocksize = 1024;
	while (scalar keys %hltodo) {
		machine: for (keys %hltodo) {
			my $out = $hl->{$_}->{chld_out};
			# begin to read
			my $bytes_read = -1;
			while ($bytes_read) {
				my $buf;
				my $bytes_read = sysread($out, $buf, $blocksize);
				if (defined($bytes_read)) {
					if ($bytes_read == 0) {
						# eof
						close($out);
						last;
					} else {
				$hl->{$_}->{data}.= $buf;
					}
				} else {
					if ($! == EAGAIN()) {
						# retry
						$hl->{$_}->{retry}++;
						$hl->{$_}->{retries}++;
						if ($hl->{$_}->{retry}) {
							$hl->{$_}->{retry} = 0;
							next machine;
						}
						usleep 10;
					} else {
						last;
					}
				}
			}
			delete $hl->{$_}->{"chld_out"};
			delete $hltodo{$_};
		}
		# kill remaining pids if timeout reached
		if ($opt{timeout} && time > $start + $opt{timeout}) {
			print STDERR "Timeout for: ", join (" ", keys %hltodo), " killing ", join (" ", values %hltodo) ;
			kill 1, values %hltodo;
			%hltodo = ();
		}
	}