www::robotrules.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "WWW::RobotRules 3"
.TH WWW::RobotRules 3 "2005-09-21" "perl v5.10.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
WWW::RobotRules \- database of robots.txt\-derived permissions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& use WWW::RobotRules;
\& my $rules = WWW::RobotRules\->new(\*(AqMOMspider/1.0\*(Aq);
\&
\& 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 $robots_txt;
\& }
\&
\& # Now we can check if a URL is valid for those servers
\& # whose "robots.txt" files we\*(Aqve gotten and parsed:
\& if($rules\->allowed($url)) {
\&     $c = get $url;
\&     ...
\& }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module parses \fI/robots.txt\fR files as specified in
\&\*(L"A Standard for Robot Exclusion\*(R", at
<http://www.robotstxt.org/wc/norobots.html>
Webmasters can use the \fI/robots.txt\fR file to forbid conforming
robots from accessing parts of their web site.
.PP
The parsed files are kept in a WWW::RobotRules object, and this object
provides methods to check if access to a given \s-1URL\s0 is prohibited.  The
same WWW::RobotRules object can be used for one or more parsed
\&\fI/robots.txt\fR files on any number of hosts.
.PP
The following methods are provided:
.ie n .IP "$rules = WWW::RobotRules\->new($robot_name)" 4
.el .IP "\f(CW$rules\fR = WWW::RobotRules\->new($robot_name)" 4
.IX Item "$rules = WWW::RobotRules->new($robot_name)"
This is the constructor for WWW::RobotRules objects.  The first
argument given to \fInew()\fR is the name of the robot.
.ie n .IP "$rules\fR\->parse($robot_txt_url, \f(CW$content\fR, \f(CW$fresh_until)" 4
.el .IP "\f(CW$rules\fR\->parse($robot_txt_url, \f(CW$content\fR, \f(CW$fresh_until\fR)" 4
.IX Item "$rules->parse($robot_txt_url, $content, $fresh_until)"
The \fIparse()\fR method takes as arguments the \s-1URL\s0 that was used to
retrieve the \fI/robots.txt\fR file, and the contents of the file.
.ie n .IP "$rules\->allowed($uri)" 4
.el .IP "\f(CW$rules\fR\->allowed($uri)" 4
.IX Item "$rules->allowed($uri)"
Returns \s-1TRUE\s0 if this robot is allowed to retrieve this \s-1URL\s0.
.ie n .IP "$rules\->agent([$name])" 4
.el .IP "\f(CW$rules\fR\->agent([$name])" 4
.IX Item "$rules->agent([$name])"
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.
.SH "ROBOTS.TXT"
.IX Header "ROBOTS.TXT"
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> ):
.PP
The file consists of one or more records separated by one or more
blank lines. Each record contains lines of the form
.PP
.Vb 1
\&  <field\-name>: <value>
.Ve
.PP
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:
.IP "User-Agent" 3
.IX 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 \fIUser-Agent\fR 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.
.Sp
The \fIUser-Agent\fR fields must occur before the \fIDisallow\fR fields.  If a
record contains a \fIUser-Agent\fR field after a \fIDisallow\fR field, that
constitutes a malformed record.  This parser will assume that a blank
line should have been placed before that \fIUser-Agent\fR field, and will
break the record into two.  All the fields before the \fIUser-Agent\fR field
will constitute a record, and the \fIUser-Agent\fR field will be the first
field in a new record.
.IP "Disallow" 3
.IX Item "Disallow"
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
.SH "ROBOTS.TXT EXAMPLES"
.IX Header "ROBOTS.TXT EXAMPLES"
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":
.PP
.Vb 3
\&  User\-agent: *
\&  Disallow: /cyberworld/map/ # This is an infinite virtual URL space
\&  Disallow: /tmp/ # these will soon disappear
.Ve
.PP
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":
.PP
.Vb 2
\&  User\-agent: *
\&  Disallow: /cyberworld/map/ # This is an infinite virtual URL space
\&
\&  # Cybermapper knows where to go.
\&  User\-agent: cybermapper
\&  Disallow:
.Ve
.PP
This example indicates that no robots should visit this site further:
.PP
.Vb 3
\&  # go away
\&  User\-agent: *
\&  Disallow: /
.Ve
.PP
This is an example of a malformed robots.txt file.
.PP
.Vb 10
\&  # robots.txt for ancientcastle.example.com
\&  # I\*(Aqve 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\*(Aqs good to be the Prince...
\&  User\-agent: Beast
\&  Disallow:
.Ve
.PP
This file is missing the required blank lines between records.
However, the intention is clear.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
LWP::RobotUA, WWW::RobotRules::AnyDBM_File