Database of robots.txt-derived permissions
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;
...
}
This module parses /robots.txt files as specified in \*(L"A Standard for Robot Exclusion\*(R", 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 \s-1URL\s0 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: This is the constructor for WWW::RobotRules objects. The first argument given to new() is the name of the robot. The parse() method takes as arguments the \s-1URL\s0 that was used to retrieve the /robots.txt file, and the contents of the file. Returns \s-1TRUE\s0 if this robot is allowed to retrieve this \s-1URL\s0. Get/set the agent name. \s-1NOTE:\s0 Changing the agent name will clear the robots.txt rules and expire times out of the cache.
The format and semantics of the \*(L"/robots.txt\*(R" 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:
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.
The value of this field specifies a partial \s-1URL\s0 that is not to be visited. This can be a full path, or a partial path; any \s-1URL\s0 that starts with this value will not be retrieved
Unrecognized records are ignored.
The following example \*(L"/robots.txt\*(R" file specifies that no robots should visit any \s-1URL\s0 starting with \*(L"/cyberworld/map/\*(R" or \*(L"/tmp/\*(R":
User-agent: * Disallow: /cyberworld/map/ # This is an infinite virtual URL space Disallow: /tmp/ # these will soon disappear
This example \*(L"/robots.txt\*(R" file specifies that no robots should visit any \s-1URL\s0 starting with \*(L"/cyberworld/map/\*(R", except the robot called \*(L"cybermapper\*(R":
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.
LWP::RobotUA, WWW::RobotRules::AnyDBM_File
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.