# man > WWW::RobotRules(3pm)

## NAME
    [WWW::RobotRules](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown) - database of robots.txt-derived permissions

## SYNOPSIS
     use [WWW::RobotRules](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown);
     my $rules = [WWW::RobotRules](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown)->new('MOMspider/1.0');

     use [LWP::Simple](https://www.chedong.com/phpMan.php/perldoc/LWP%3A%3ASimple/markdown) 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](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown) object, and this object provides methods to check
    if access to a given URL is prohibited. The same [WWW::RobotRules](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown) object can be used for one or
    more parsed /robots.txt files on any number of hosts.

    The following methods are provided:

    $rules = [WWW::RobotRules](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown)->new($robot_name)
        This is the constructor for [WWW::RobotRules](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules/markdown) 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](https://www.chedong.com/phpMan.php/perldoc/LWP%3A%3ARobotUA/markdown), [WWW::RobotRules::AnyDBM_File](https://www.chedong.com/phpMan.php/perldoc/WWW%3A%3ARobotRules%3A%3AAnyDBMFile/markdown)

## 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.