package WWW::RobotRules;
$VERSION = "5.832";
sub Version { $VERSION; }
use strict;
use URI ();
sub new {
my($class, $ua) = @_;
# This ugly hack is needed to ensure backwards compatibility.
# The "WWW::RobotRules" class is now really abstract.
$class = "WWW::RobotRules::InCore" if $class eq "WWW::RobotRules";
my $self = bless { }, $class;
$self->agent($ua);
$self;
}
sub parse {
my($self, $robot_txt_uri, $txt, $fresh_until) = @_;
$robot_txt_uri = URI->new("$robot_txt_uri");
my $netloc = $robot_txt_uri->host . ":" . $robot_txt_uri->port;
$self->clear_rules($netloc);
$self->fresh_until($netloc, $fresh_until || (time + 365*24*3600));
my $ua;
my $is_me = 0; # 1 iff this record is for me
my $is_anon = 0; # 1 iff this record is for *
my $seen_disallow = 0; # watch for missing record separators
my @me_disallowed = (); # rules disallowed for me
my @anon_disallowed = (); # rules disallowed for *
# blank lines are significant, so turn CRLF into LF to avoid generating
# false ones
$txt =~ s/\015\012/\012/g;
# split at \012 (LF) or \015 (CR) (Mac text files have just CR for EOL)
for(split(/[\012\015]/, $txt)) {
# Lines containing only a comment are discarded completely, and
# therefore do not indicate a record boundary.
next if /^\s*\#/;
s/\s*\#.*//; # remove comments at end-of-line
if (/^\s*$/) { # blank line
last if $is_me; # That was our record. No need to read the rest.
$is_anon = 0;
$seen_disallow = 0;
}
elsif (/^\s*User-Agent\s*:\s*(.*)/i) {
$ua = $1;
$ua =~ s/\s+$//;
if ($seen_disallow) {
# treat as start of a new record
$seen_disallow = 0;
last if $is_me; # That was our record. No need to read the rest.
$is_anon = 0;
}
if ($is_me) {
# This record already had a User-agent that
# we matched, so just continue.
}
elsif ($ua eq '*') {
$is_anon = 1;
}
elsif($self->is_me($ua)) {
$is_me = 1;
}
}
elsif (/^\s*Disallow\s*:\s*(.*)/i) {
unless (defined $ua) {
warn "RobotRules <$robot_txt_uri>: Disallow without preceding User-agent\n" if $^W;
$is_anon = 1; # assume that User-agent: * was intended
}
my $disallow = $1;
$disallow =~ s/\s+$//;
$seen_disallow = 1;
if (length $disallow) {
my $ignore;
eval {
my $u = URI->new_abs($disallow, $robot_txt_uri);
$ignore++ if $u->scheme ne $robot_txt_uri->scheme;
$ignore++ if lc($u->host) ne lc($robot_txt_uri->host);
$ignore++ if $u->port ne $robot_txt_uri->port;
$disallow = $u->path_query;
$disallow = "/" unless length $disallow;
};
next if $@;
next if $ignore;
}
if ($is_me) {
push(@me_disallowed, $disallow);
}
elsif ($is_anon) {
push(@anon_disallowed, $disallow);
}
}
elsif (/\S\s*:/) {
# ignore
}
else {
warn "RobotRules <$robot_txt_uri>: Malformed record: <$_>\n" if $^W;
}
}
if ($is_me) {
$self->push_rules($netloc, @me_disallowed);
}
else {
$self->push_rules($netloc, @anon_disallowed);
}
}
#
# Returns TRUE if the given name matches the
# name of this robot
#
sub is_me {
my($self, $ua_line) = @_;
my $me = $self->agent;
# See whether my short-name is a substring of the
# "User-Agent: ..." line that we were passed:
if(index(lc($me), lc($ua_line)) >= 0) {
return 1;
}
else {
return '';
}
}
sub allowed {
my($self, $uri) = @_;
$uri = URI->new("$uri");
return 1 unless $uri->scheme eq 'http' or $uri->scheme eq 'https';
# Robots.txt applies to only those schemes.
my $netloc = $uri->host . ":" . $uri->port;
my $fresh_until = $self->fresh_until($netloc);
return -1 if !defined($fresh_until) || $fresh_until < time;
my $str = $uri->path_query;
my $rule;
for $rule ($self->rules($netloc)) {
return 1 unless length $rule;
return 0 if index($str, $rule) == 0;
}
return 1;
}
# The following methods must be provided by the subclass.
sub agent;
sub visit;
sub no_visits;
sub last_visits;
sub fresh_until;
sub push_rules;
sub clear_rules;
sub rules;
sub dump;
package WWW::RobotRules::InCore;
use vars qw(@ISA);
@ISA = qw(WWW::RobotRules);
sub agent {
my ($self, $name) = @_;
my $old = $self->{'ua'};
if ($name) {
# Strip it so that it's just the short name.
# I.e., "FooBot" => "FooBot"
# "FooBot/1.2" => "FooBot"
# "FooBot/1.2 [http://foobot.int; foo@bot.int]" => "FooBot"
$name = $1 if $name =~ m/(\S+)/; # get first word
$name =~ s!/.*!!; # get rid of version
unless ($old && $old eq $name) {
delete $self->{'loc'}; # all old info is now stale
$self->{'ua'} = $name;
}
}
$old;
}
sub visit {
my($self, $netloc, $time) = @_;
return unless $netloc;
$time ||= time;
$self->{'loc'}{$netloc}{'last'} = $time;
my $count = \$self->{'loc'}{$netloc}{'count'};
if (!defined $$count) {
$$count = 1;
}
else {
$$count++;
}
}
sub no_visits {
my ($self, $netloc) = @_;
$self->{'loc'}{$netloc}{'count'};
}
sub last_visit {
my ($self, $netloc) = @_;
$self->{'loc'}{$netloc}{'last'};
}
sub fresh_until {
my ($self, $netloc, $fresh_until) = @_;
my $old = $self->{'loc'}{$netloc}{'fresh'};
if (defined $fresh_until) {
$self->{'loc'}{$netloc}{'fresh'} = $fresh_until;
}
$old;
}
sub push_rules {
my($self, $netloc, @rules) = @_;
push (@{$self->{'loc'}{$netloc}{'rules'}}, @rules);
}
sub clear_rules {
my($self, $netloc) = @_;
delete $self->{'loc'}{$netloc}{'rules'};
}
sub rules {
my($self, $netloc) = @_;
if (defined $self->{'loc'}{$netloc}{'rules'}) {
return @{$self->{'loc'}{$netloc}{'rules'}};
}
else {
return ();
}
}
sub dump
{
my $self = shift;
for (keys %$self) {
next if $_ eq 'loc';
print "$_ = $self->{$_}\n";
}
for (keys %{$self->{'loc'}}) {
my @rules = $self->rules($_);
print "$_: ", join("; ", @rules), "\n";
}
}
1;
__END__
# Bender: "Well, I don't have anything else
# planned for today. Let's get drunk!"
=head1 NAME
WWW::RobotRules - database of robots.txt-derived permissions
=head1 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;
...
}
=head1 DESCRIPTION
This module parses F files as specified in
"A Standard for Robot Exclusion", at
Webmasters can use the F 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
F files on any number of hosts.
The following methods are provided:
=over 4
=item $rules = WWW::RobotRules->new($robot_name)
This is the constructor for WWW::RobotRules objects. The first
argument given to new() is the name of the robot.
=item $rules->parse($robot_txt_url, $content, $fresh_until)
The parse() method takes as arguments the URL that was used to
retrieve the F file, and the contents of the file.
=item $rules->allowed($uri)
Returns TRUE if this robot is allowed to retrieve this URL.
=item $rules->agent([$name])
Get/set the agent name. NOTE: Changing the agent name will clear the robots.txt
rules and expire times out of the cache.
=back
=head1 ROBOTS.TXT
The format and semantics of the "/robots.txt" file are as follows
(this is an edited abstract of
):
The file consists of one or more records separated by one or more
blank lines. Each record contains lines of the form
:
The field name is case insensitive. Text after the '#' character on a
line is ignored during parsing. This is used for comments. The
following can be used:
=over 3
=item User-Agent
The value of this field is the name of the robot the record is
describing access policy for. If more than one I 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 I fields must occur before the I fields. If a
record contains a I field after a I field, that
constitutes a malformed record. This parser will assume that a blank
line should have been placed before that I field, and will
break the record into two. All the fields before the I field
will constitute a record, and the I field will be the first
field in a new record.
=item 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
=back
Unrecognized records are ignored.
=head1 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.
=head1 SEE ALSO
L, L