/usr/man2/cat.3/WWW::RobotRules.3.Z

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> Web-
       masters 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 /ro-
       bots.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 fol-
       lowing <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 con-
          stitutes 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

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.  How-
       ever, the intention is clear.

SEE ALSO

       LWP::RobotUA, WWW::RobotRules::AnyDBM_File

perl v5.8.8                       2004-04-06                WWW::RobotRules(3)
See also WWW::RobotRules::AnyDBM_File(3)