Ubuntu Manpage: WWW::RobotRules - database of robots.txt-derived permissions

Provided by: libwww-robotrules-perl_6.02-1_all

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.

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