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.