sub watch_callback {
    my ($fd, $condition, $fh) = @_;
    if ($condition >= 'in') {
        my $data = scalar <$fh>;
        if (defined $data) {
            my $buffer = $textview1->get_buffer;
            $buffer->insert ($buffer->get_end_iter, $data);
        }
    }
    if ($condition >= 'hup' or $condition >= 'err') {
        $fh->close;
        $fh = undef;
    }

    if ($fh) {
        return TRUE;
    } else {
        return FALSE;
    }
}