WWW::Search - Virtual base class for WWW searches
This class is the parent for all access method supported by the WWW::Search library.
WWW::Search
Search results are limited and there is a pause between each request for results to avoid overloading either the client or the server.
Using the library should be straightforward: Here's a sample program:
my($search) = new WWW::Search::AltaVista; $search->native_query(WWW::Search::escape_query($query)); my($result); while ($result = $search->next_result()) { print $result->url, "\n"; };
Results are objects of WWW::SearchResult (see WWW::SearchResult) .
WWW::SearchResult
For more details see LWP.
To create a new WWW::Search, call $search = new WWW::Search::SearchEngineName(); where SearchEngineName is replaced with a particular search engine. For example: $search = new WWW::Search::AltaVista();
The next step is usually: $search->native_query('search-engine-specific query string');
Specify a query to the current search object. Doesn't actually begin the search until results or next_result is called.
results
next_result
Example: $search->native_query('search-engine-specific query string');
The next step is usually:
@results = $search->results();
or
while ($result = $search->next_result()) { # do_something; };
Return all the results of a query as a reference to array of SearchResult objects.
Example: @results = $search->results(); foreach $result (@results) { print $result->url(), "\n"; };
Return each result of a query as a SearchResult object.
Example: while ($result = $search->next_result()) { print $result->url(), "\n"; };
seek_result($offset)
Set which result next_result should return (like lseek in Unix). Results are zero-indexed.
lseek
The only guaranteed valid offset is 0 which will replay the results from the beginning. In particular, seeking past the end of the current cached results probably won't do what you might think it should.
Results are cached, so this doesn't re-issue the query or cause IO (unless you go off the end of the results). To re-do the query, create a new search object.
Example: $search->seek_result(0);
The maximum number of hits to return (approximately). Queries resulting in more than this many hits will return the first hits, up to this limit.
Defaults to 500.
Example: $max = $seach->maximum_to_retrieve(100);
Escape a query. Before queries are made special characters must be escaped so that a proper URL can be formed.
This is like escaping a URL but "+" is a protected character and spaces are converted to "+"'s.
Example: $escaped = Search::escape_query('+lsam +replication'); (Returns "%22lsam+replication%22").
See also unescape_query.
unescape_query
Unescape a query. See escape_query for details.
escape_query
Example: $unescaped = Search::unescape_query('%22lsam+replication%22'); (Returns "+lsam +replication").
This internal routine does generic Search setup. It calls native_setup_search to do back-end specific setup.
native_setup_search
This internal routine does setup for a user-agent for dervived classes that use the web.
Derived classes should call this between requests to remote servers to avoid overloading them with many, fast back-to-back requests.
An internal routine to interface with native_retrieve_some. Checks for overflow.
native_retrieve_some
WWW::Search supports back-ends to separate search engines. Each back-end is implemented as a subclass of WWW::Search.
A back-end usually has two routines, native_retrieve_some and native_setup_search.
native_retrieve_some is the core of a back-end. It will be called periodically to fetch URLs. Each call it should fetch a page with about 10 or so hits and add them to the cache. It should return the number of hits found or undef when there are no more hits.
Internally, native_retrieve_some typically will parse the HTML, extract the links and descriptions, then find the ``next'' button and save the URL. See the code for the AltaVista implementation for an example.
native_setup_search is invoked before the search. It is passed a single argument: the escaped, native version of the query.
The front- and back-ends share a single object (a hash) The back-end can change any hash element beginning with underscore, and {response} (an HTTP::Response code) and {cache} (an array of WWW::SearchResult objects to which it should append new results).
{response}
HTTP::Response
{cache}
If you implement a new back-end, please let the authors know.
WWW::Search is written by John Heidemann, <johnh@isi.edu>.
Copyright (c) 1996 University of Southern California. All rights reserved.
Redistribution and use in source and binary forms are permitted provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation, advertising materials, and other materials related to such distribution and use acknowledge that the software was developed by the University of Southern California, Information Sciences Institute. The name of the University may not be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
To install WWW::Search, copy and paste the appropriate command in to your terminal.
cpanm
cpanm WWW::Search
CPAN shell
perl -MCPAN -e shell install WWW::Search
For more information on module installation, please visit the detailed CPAN module installation guide.