WWW::RobotRules3pm

Usage

    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;
        ...
    }

Overview

This module parses /robots.txt files as specified in at <https://www.robotstxt.org/robotstxt.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:

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 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.