Section: User Contributed Perl Documentation (3pm)
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LWP::RobotUA - a class for well-behaved Web robots
my $ua = LWP::RobotUA->new('my-robot/0.1', 'email@example.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 = $ua->get('http://whatever.int/...');
This class implements a user agent that is suitable for robot
applications. Robots should be nice to the servers they visit. They
should consult the /robots.txt
file to ensure that they are welcomed
and they should not make requests too frequently.
But before you consider writing a robot, take a look at
When you use an LWP::RobotUA object as your user agent, then you do not
really have to think about these things yourself; "robots.txt" files
are automatically consulted and obeyed, the server isn't queried
too rapidly, and so on. Just send requests
as you do when you are using a normal LWP::UserAgent
object (using "$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
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.
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.
- SEE ALSO