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GNU/Linux |
RedHat 9.0(Shrike) |
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WWW::RobotRules(3pm) |
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WWW::RobotsRules − Parse robots.txt files
require WWW::RobotRules;
my $robotsrules = new WWW::RobotRules ’MOMspider/1.0’;
use LWP::Simple qw(get);
$url = "http://some.place/robots.txt";
my $robots_txt = get $url;
$robotsrules->parse($url, $robots_txt);
$url = "http://some.other.place/robots.txt";
my $robots_txt = get $url;
$robotsrules->parse($url, $robots_txt);
# Now we are able to check if a URL is valid for those servers that
# we have obtained and parsed "robots.txt" files for.
if($robotsrules->allowed($url)) {
$c = get $url;
...
}
This module parses a /robots.txt file as specified in "A Standard for Robot Exclusion", described in <http://info.webcrawler.com/mak/projects/robots/norobots.html> Webmasters can use the /robots.txt file to disallow conforming robots access to parts of their web site.
The parsed file is kept in the WWW::RobotRules object, and this object provides methods to check if access to a given URL is prohibited. The same WWW::RobotRules object can parse multiple /robots.txt files.
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://info.webcrawler.com/mak/projects/robots/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
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WWW::RobotRules(3pm) | |