Section: User Contributed Perl Documentation (3pm)
Updated: 2014-04-23
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LWP::RobotUA - a class for well-behaved Web robots  


  use LWP::RobotUA;
  my $ua = LWP::RobotUA->new('my-robot/0.1', 'me@foo.com');
  $ua->delay(10);  # be very nice -- max one hit every ten minutes!

  # Then just use it just like a normal LWP::UserAgent:
  my $response = $ua->get('http://whatever.int/...');



This class implements a user agent that is suitable for robot applications. Robots should be nice to the servers they visit. They should consult the /robots.txt file to ensure that they are welcomed and they should not make requests too frequently.

But before you consider writing a robot, take a look at <URL:http://www.robotstxt.org/>.

When you use an LWP::RobotUA object as your user agent, then you do not really have to think about these things yourself; "robots.txt" files are automatically consulted and obeyed, the server isn't queried too rapidly, and so on. Just send requests as you do when you are using a normal LWP::UserAgent object (using "$ua->get(...)", "$ua->head(...)", "$ua->request(...)", etc.), and this special agent will make sure you are nice.  


The LWP::RobotUA is a sub-class of LWP::UserAgent and implements the same methods. In addition the following methods are provided:
$ua = LWP::RobotUA->new( %options )
$ua = LWP::RobotUA->new( $agent, $from )
$ua = LWP::RobotUA->new( $agent, $from, $rules )
The LWP::UserAgent options "agent" and "from" are mandatory. The options "delay", "use_sleep" and "rules" initialize attributes private to the RobotUA. If "rules" are not provided, then "WWW::RobotRules" is instantiated providing an internal database of robots.txt.

It is also possible to just pass the value of "agent", "from" and optionally "rules" as plain positional arguments.

$ua->delay( $minutes )
Get/set the minimum delay between requests to the same server, in minutes. The default is 1 minute. Note that this number doesn't have to be an integer; for example, this sets the delay to 10 seconds:


$ua->use_sleep( $boolean )
Get/set a value indicating whether the UA should sleep() if requests arrive too fast, defined as $ua->delay minutes not passed since last request to the given server. The default is TRUE. If this value is FALSE then an internal SERVICE_UNAVAILABLE response will be generated. It will have a Retry-After header that indicates when it is OK to send another request to this server.
$ua->rules( $rules )
Set/get which WWW::RobotRules object to use.
$ua->no_visits( $netloc )
Returns the number of documents fetched from this server host. Yeah I know, this method should probably have been named num_visits() or something like that. :-(
$ua->host_wait( $netloc )
Returns the number of seconds (from now) you must wait before you can make a new request to this host.
Returns a string that describes the state of the UA. Mainly useful for debugging.


LWP::UserAgent, WWW::RobotRules  


Copyright 1996-2004 Gisle Aas.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.