NAME
    WWW::RobotRules - database of robots.txt-derived permissions

SYNOPSIS
     use WWW::RobotRules;
     my $rules = WWW::RobotRules->new('MOMspider/1.0');

     use LWP::Simple qw(get);

     {
       my $url = "http://some.place/robots.txt";
       my $robots_txt = get $url;
       $rules->parse($url, $robots_txt) if defined $robots_txt;
     }

     {
       my $url = "http://some.other.place/robots.txt";
       my $robots_txt = get $url;
       $rules->parse($url, $robots_txt) if defined $robots_txt;
     }

     # Now we can check if a URL is valid for those servers
     # whose "robots.txt" files we've gotten and parsed:
     if($rules->allowed($url)) {
         $c = get $url;
         ...
     }

DESCRIPTION
    This module parses /robots.txt files as specified in "A Standard for
    Robot Exclusion", at <http://www.robotstxt.org/wc/norobots.html>
    Webmasters can use the /robots.txt file to forbid conforming robots from
    accessing parts of their web site.

    The parsed files are kept in a WWW::RobotRules object, and this object
    provides methods to check if access to a given URL is prohibited. The
    same WWW::RobotRules object can be used for one or more parsed
    /robots.txt files on any number of hosts.

    The following methods are provided:

    $rules = WWW::RobotRules->new($robot_name)
        This is the constructor for WWW::RobotRules objects. The first
        argument given to new() is the name of the robot.

    $rules->parse($robot_txt_url, $content, $fresh_until)
        The parse() method takes as arguments the URL that was used to
        retrieve the /robots.txt file, and the contents of the file.

    $rules->allowed($uri)
        Returns TRUE if this robot is allowed to retrieve this URL.

    $rules->agent([$name])
        Get/set the agent name. NOTE: Changing the agent name will clear the
        robots.txt rules and expire times out of the cache.

ROBOTS.TXT
    The format and semantics of the "/robots.txt" file are as follows (this
    is an edited abstract of <http://www.robotstxt.org/wc/norobots.html>):

    The file consists of one or more records separated by one or more blank
    lines. Each record contains lines of the form

      <field-name>: <value>

    The field name is case insensitive. Text after the '#' character on a
    line is ignored during parsing. This is used for comments. The following
    <field-names> can be used:

    User-Agent
       The value of this field is the name of the robot the record is
       describing access policy for. If more than one *User-Agent* field is
       present the record describes an identical access policy for more than
       one robot. At least one field needs to be present per record. If the
       value is '*', the record describes the default access policy for any
       robot that has not not matched any of the other records.

       The *User-Agent* fields must occur before the *Disallow* fields. If a
       record contains a *User-Agent* field after a *Disallow* field, that
       constitutes a malformed record. This parser will assume that a blank
       line should have been placed before that *User-Agent* field, and will
       break the record into two. All the fields before the *User-Agent*
       field will constitute a record, and the *User-Agent* field will be
       the first field in a new record.

    Disallow
       The value of this field specifies a partial URL that is not to be
       visited. This can be a full path, or a partial path; any URL that
       starts with this value will not be retrieved

    Unrecognized records are ignored.

ROBOTS.TXT EXAMPLES
    The following example "/robots.txt" file specifies that no robots should
    visit any URL starting with "/cyberworld/map/" or "/tmp/":

      User-agent: *
      Disallow: /cyberworld/map/ # This is an infinite virtual URL space
      Disallow: /tmp/ # these will soon disappear

    This example "/robots.txt" file specifies that no robots should visit
    any URL starting with "/cyberworld/map/", except the robot called
    "cybermapper":

      User-agent: *
      Disallow: /cyberworld/map/ # This is an infinite virtual URL space

      # Cybermapper knows where to go.
      User-agent: cybermapper
      Disallow:

    This example indicates that no robots should visit this site further:

      # go away
      User-agent: *
      Disallow: /

    This is an example of a malformed robots.txt file.

      # robots.txt for ancientcastle.example.com
      # I've locked myself away.
      User-agent: *
      Disallow: /
      # The castle is your home now, so you can go anywhere you like.
      User-agent: Belle
      Disallow: /west-wing/ # except the west wing!
      # It's good to be the Prince...
      User-agent: Beast
      Disallow:

    This file is missing the required blank lines between records. However,
    the intention is clear.

SEE ALSO
    LWP::RobotUA, WWW::RobotRules::AnyDBM_File

COPYRIGHT
      Copyright 1995-2009, Gisle Aas
      Copyright 1995, Martijn Koster

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.