# phpman > perldoc > IO::Socket::SSL::PublicSuffix

## NAME
    [IO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown) - provide access to Mozilla's list of effective TLD names

## SYNOPSIS
        # use builtin default
        use [IO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown);
        $ps = [IO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown)->default;

        # load from string
        $ps = [IO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown)->from_string("*.uk\n*");

        # load from file or file handle
        $ps = [IO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown)->from_file($filename);
        $ps = [IO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown)->from_file(\*STDIN);


        # --- string in -> string out
        # $rest -> whatever.host
        # $tld  -> co.uk
        my ($rest,$tld) = $ps->public_suffix('whatever.host.co.uk');
        my $tld = $ps->public_suffix('whatever.host.co.uk');

        # $root_domain -> host.co.uk
        my $root_domain = $ps->public_suffix('whatever.host.co.uk', 1);

        # --- array in -> array out
        # $rest -> [qw(whatever host)]
        # $tld  -> [qw(co uk)]
        my ($rest,$tld) = $ps->public_suffix([qw(whatever host co uk)]);

     ----

        # To update this file with the current list:
        perl -[MIO::Socket::SSL::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/MIO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix/markdown) -e '[IO::Socket::SSL::PublicSuffix::update_self_from_url](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL%3A%3APublicSuffix%3A%3Aupdateselffromurl/markdown)()'

## DESCRIPTION
    This module uses the list of effective top level domain names from the mozilla project to
    determine the public top level domain for a given hostname.

### Method
    class->default(%args)
        Returns object with builtin default. "min_suffix" can be given in %args to specify the
        minimal suffix, default is 1.

    class->from_string(string,%args)
        Returns object with configuration from string. See method "default" for %args.

    class->from_file( file name| file handle, %args )
        Returns object with configuration from file or file handle. See method "default" for %args.

    $self->public_suffix( $host|\@host, [ $add ] )
        In array context the function returns the non-tld part and the tld part of the given
        hostname, in scalar context only the tld part. It adds $add parts of the non-tld part to the
        tld, e.g. with "$add=1" it will return the root domain.

        If there were no explicit matches against the public suffix configuration it will fall back
        to a suffix of length 1.

        The function accepts a string or an array-ref (e.g. host split by "."). In the first case it
        will return string(s), in the latter case array-ref(s).

        International hostnames or labels can be in ASCII (IDNA form starting with "xn--") or
        unicode. In the latter case an IDNA handling library needs to be available. URI is
        preferred, but [Net::IDN](https://www.chedong.com/phpMan.php/perldoc/Net%3A%3AIDN/markdown):::Encode, [Net::LibIDN](https://www.chedong.com/phpMan.php/perldoc/Net%3A%3ALibIDN/markdown) are still supported.

    ($self|class)->can_idn
        Returns true if IDN support is available.

## FILES
    <http://publicsuffix.org/list/effective_tld_names.dat>

## SEE ALSO
    [Domain::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/Domain%3A%3APublicSuffix/markdown), [Mozilla::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/Mozilla%3A%3APublicSuffix/markdown)

## BUGS
     Q: Why yet another module, we already have L<[Domain::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/Domain%3A%3APublicSuffix/markdown)> and
        L<[Mozilla::PublicSuffix](https://www.chedong.com/phpMan.php/perldoc/Mozilla%3A%3APublicSuffix/markdown)>.
     A: Because the public suffix data change more often than these modules do,
        [IO::Socket::SSL](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASocket%3A%3ASSL/markdown) needs this list and it is more easy this way to keep it
        up-to-date.

## AUTHOR
    Steffen Ullrich