WWW::RobotRules

WWW::RobotRules(3)   User Contributed Perl Documentation   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> 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
       /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.robot-
       stxt.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
	  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

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			  2008-04-07		   WWW::RobotRules(3)