LWP::RobotUA - a class for well-behaved Web robots
my $ua = LWP::RobotUA->new('my-robot/0.1', 'firstname.lastname@example.org');
$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 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:
my $ua = LWP::RobotUA->new( %options )
my $ua = LWP::RobotUA->new( $agent, $from )
my $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.
my $delay = $ua->delay;
$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:
my $bool = $ua->use_sleep;
$ua->use_sleep( $boolean );
Get/set a value indicating whether the UA should "sleep" in LWP::RobotUA 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.
my $rules = $ua->rules;
$ua->rules( $rules );
Set/get which WWW::RobotRules object to use.
my $num = $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. :-(
my $num = $ua->host_wait( $netloc )
Returns the number of seconds (from now) you must wait before you can make a new request to this host.
my $string = $ua->as_string;
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.
To install LWP, copy and paste the appropriate command in to your terminal.
perl -MCPAN -e shell
For more information on module installation, please visit the detailed CPAN module installation guide.