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.