NAME

WWW::RobotsRules - Parse robots.txt files

SYNOPSIS

 require WWW::RobotRules;
 my $robotsrules = new WWW::RobotRules 'MOMspider/1.0';

 use LWP::Simple qw(get);

 $url = "http://some.place/robots.txt";;
 my $robots_txt = get $url;
 $robotsrules->parse($url, $robots_txt);

 $url = "http://some.other.place/robots.txt";;
 my $robots_txt = get $url;
 $robotsrules->parse($url, $robots_txt);

 # Now we are able to check if a URL is valid for those servers that
 # we have obtained and parsed "robots.txt" files for.
 if($robotsrules->allowed($url)) {
     $c = get $url;
     ...
 }

DESCRIPTION

This module parses a robots.txt file as specified in ``A Standard for Robot Exclusion'', described in <URL:http://info.webcrawler.com/mak/projects/robots/norobots.html> Webmasters can use the robots.txt file to disallow conforming robots access to parts of their WWW server.

The parsed file is kept in the WWW::RobotRules object, and this object provide methods to check if access to a given URL is prohibited. The same WWW::RobotRules object can parse multiple robots.txt files.

METHODS

$rules = new WWW::RobotRules 'MOMspider/1.0'

This is the constructor for WWW::RobotRules objects. The first argument given to new() is the name of the robot.

$rules->parse($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.

$rules->allowed($url)

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 <URL:http://info.webcrawler.com/mak/projects/robots/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.
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

Examples

The following example ``/robots.txt'' file specifies that no robots should visit any URL starting with ``/cyberworld/map/'' or ``/tmp/'':

  # robots.txt for http://www.site.com/

  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'':

  # robots.txt for http://www.site.com/

  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: /