GNU/Linux |
CentOS 4.8 |
i386 |
WWW::RobotRules(3pm) |
WWW::RobotRules − 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 "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.
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.
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
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: /
LWP::RobotUA, WWW::RobotRules::AnyDBM_File
WWW::RobotRules(3pm) |