WWW::RobotRules(3)

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.

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

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: /

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