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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<title>SWISH-Enhanced: spider.pl - Example Perl program to spider web servers </title>
<link href="./style.css" rel=stylesheet type="text/css" title="refstyle">
</head>
<body>
<h1 class="banner">
<a href="http://swish-e.org"><img border=0 src="images/swish.gif" alt="Swish-E Logo"></a><br>
<img src="images/swishbanner1.gif"><br>
<img src="images/dotrule1.gif"><br>
spider.pl - Example Perl program to spider web servers
</h1>
<hr>
<p>
<div class="navbar">
<a href="./search.html">Prev</a> |
<a href="./index.html">Contents</a> |
<a href="./Filter.html">Next</a>
</div>
<p>
<div class="toc">
<A NAME="toc"></A>
<P><B>Table of Contents:</B></P>
<UL>
<LI><A HREF="#SYNOPSIS">SYNOPSIS</A>
<LI><A HREF="#DESCRIPTION">DESCRIPTION</A>
<UL>
<LI><A HREF="#Running_the_spider">Running the spider</A>
<LI><A HREF="#Robots_Exclusion_Rules_and_being_nice">Robots Exclusion Rules and being nice</A>
<LI><A HREF="#Duplicate_Documents">Duplicate Documents</A>
<LI><A HREF="#Broken_relative_links">Broken relative links</A>
<LI><A HREF="#Compression">Compression</A>
</UL>
<LI><A HREF="#REQUIREMENTS">REQUIREMENTS</A>
<LI><A HREF="#CONFIGURATION_FILE">CONFIGURATION FILE</A>
<LI><A HREF="#CONFIGURATION_OPTIONS">CONFIGURATION OPTIONS</A>
<LI><A HREF="#CALLBACK_FUNCTIONS">CALLBACK FUNCTIONS</A>
<UL>
<LI><A HREF="#More_on_setting_flags">More on setting flags</A>
</UL>
<LI><A HREF="#SIGNALS">SIGNALS</A>
<LI><A HREF="#CHANGES">CHANGES</A>
<UL>
<LI><A HREF="#Thu_Sep_30_2004_changes_for_Swish_e_2_4_3">Thu Sep 30 2004 - changes for Swish-e 2.4.3</A>
</UL>
<LI><A HREF="#TODO">TODO</A>
<LI><A HREF="#COPYRIGHT">COPYRIGHT</A>
<LI><A HREF="#SUPPORT">SUPPORT</A>
</UL>
</div>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<P>
<H1><A NAME="SYNOPSIS">SYNOPSIS</A></H1>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> spider.pl [<spider config file>] [<URL> ...]</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # Spider using some common defaults and capture the output
# into a file</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl default <A HREF="http://myserver.com/">http://myserver.com/</A> > output.txt</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # or using a config file</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> spider.config:
@servers = (
{
base_url => '<A HREF="http://myserver.com/">http://myserver.com/</A>',
email => 'me@myself.com',
# other spider settings described below
},
);</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl spider.config > output.txt</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # or using the default config file SwishSpiderConfig.pl
./spider.pl > output.txt</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # using with swish-e</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl spider.config | swish-e -c swish.config -S prog -i stdin</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # or in two steps
./spider.pl spider.config > output.txt
swish-e -c swish.config -S prog -i stdin < output.txt</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # or with compression
./spider.pl spider.config | gzip > output.gz
gzip -dc output.gz | swish-e -c swish.config -S prog -i stdin</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # or having swish-e call the spider directly using the
# spider config file SwishSpiderConfig.pl:
swish-e -c swish.config -S prog -i spider.pl</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # or the above but passing passing a parameter to the spider:
echo "SwishProgParameters spider.config" >> swish.config
echo "IndexDir spider.pl" >> swish.config
swish-e -c swish.config -S prog</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> Note: When running on some versions of Windows (e.g. Win ME and Win 98 SE)
you may need to tell Perl to run the spider directly:</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> perl spider.pl | swish-e -S prog -c swish.conf -i stdin</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> This pipes the output of the spider directly into swish.</pre>
</td>
</tr>
</table>
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="DESCRIPTION">DESCRIPTION</A></H1>
<P>
<EM>spider.pl</EM> is a program for fetching documnts from a web server, and outputs the
documents to STDOUT in a special format designed to be read by Swish-e.
<P>
The spider can index non-text documents such as PDF and MS Word by use of
filter (helper) programs. These programs are not part of the Swish-e
distribution and must be installed separately. See the section on filtering
below.
<P>
A configuration file is noramlly used to control what documents are fetched
from the web <CODE>server(s).</CODE> The configuration file and its options
are described below. The is also a "default" config suitable for
spidering.
<P>
The spider is designed to spider web pages and fetch documents from one
host at a time -- offsite links are not followed. But, you can configure
the spider to spider multiple sites in a single run.
<P>
<EM>spider.pl</EM> is distributed with Swish-e and is installed in the swish-e library
directory at installation time. This directory (libexedir) can be seen by
running the command:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> swish-e -h</pre>
</td>
</tr>
</table>
<P>
Typically on unix-type systems the spider is installed at:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> /usr/local/lib/swish-e/spider.pl</pre>
</td>
</tr>
</table>
<P>
This spider stores all links in memory while processing and does not do
parallel requests.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="Running_the_spider">Running the spider</A></H2>
<P>
The output from <EM>spider.pl</EM> can be captured to a temporary file which is then fed into swish-e:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl > docs.txt
swish-e -c config -S prog -i stdin < docs.txt</pre>
</td>
</tr>
</table>
<P>
or the output can be passed to swish-e via a pipe:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl | swish-e -c config -S prog -i stdin</pre>
</td>
</tr>
</table>
<P>
or the swish-e can run the spider directly:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> swish-e -c config -S prog -i spider.pl</pre>
</td>
</tr>
</table>
<P>
One advantage of having Swish-e run <EM>spider.pl</EM> is that Swish-e knows where to locate the program (based on libexecdir
compiled into swish-e).
<P>
When running the spider <EM>without</EM> any parameters it looks for a configuration file called <EM>SwishSpiderConfig.pl</EM> in the current directory. The spider will abort with an error if this file
is not found.
<P>
A configuration file can be specified as the first parameter to the spider:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl spider.config > output.txt</pre>
</td>
</tr>
</table>
<P>
If running the spider via Swish-e (i.e. Swish-e runs the spider) then use
the Swish-e config option <A HREF="././SWISH-CONFIG.html#item_SwishProgParameters">SwishProgParameters</A>
to specify the config file:
<P>
In swish.config:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> # Use spider.pl as the external program:
IndexDir spider.pl
# And pass the name of the spider config file to the spider:
SwishProgParameters spider.config</pre>
</td>
</tr>
</table>
<P>
And then run Swish-e like this:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> swish-e -c swish.config -S prog</pre>
</td>
</tr>
</table>
<P>
Finally, by using the special word "default" on the command line
the spider will use a default configuration that is useful for indexing
most sites. It's a good way to get started with the spider:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl default <A HREF="http://my_server.com/index.html">http://my_server.com/index.html</A> > output.txt</pre>
</td>
</tr>
</table>
<P>
There's no "best" way to run the spider. I like to capture to a
file and then feed that into Swish-e.
<P>
The spider does require Perl's LWP library and a few other reasonably
common modules. Most well maintained systems should have these modules
installed. See <A HREF="#REQUIREMENTS">REQUIREMENTS</A> below for more information. It's a good idea to check that you are running
a current version of these modules.
<P>
Note: the "prog" document source in Swish-e bypasses many Swish-e
configuration settings. For example, you cannot use the
<A HREF="././SWISH-CONFIG.html#item_SwishProgParameters">IndexOnly</A> directive with the "prog" document source. This is by design to
limit the overhead when using an external program for providing documents
to swish; after all, with "prog", if you don't want to index a
file, then don't give it to swish to index in the first place.
<P>
So, for spidering, if you do not wish to index images, for example, you
will need to either filter by the URL or by the content-type returned from
the web server. See <A HREF="#CALLBACK_FUNCTIONS">CALLBACK FUNCTIONS</A> below for more information.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="Robots_Exclusion_Rules_and_being_nice">Robots Exclusion Rules and being nice</A></H2>
<P>
By default, this script will not spider files blocked by <EM>robots.txt</EM>. In addition, The script will check for <meta
name="robots"..> tags, which allows finer control over what
files are indexed and/or spidered. See <A
HREF="http://www.robotstxt.org/wc/exclusion.html">http://www.robotstxt.org/wc/exclusion.html</A>
for details.
<P>
This spider provides an extension to the <meta> tag exclusion, by adding a
<STRONG>NOCONTENTS</STRONG> attribute. This attribute turns on the <CODE>no_contents</CODE> setting, which asks swish-e to only index the document's title (or file
name if not title is found).
<P>
For example:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <META NAME="ROBOTS" CONTENT="NOCONTENTS, NOFOLLOW"></pre>
</td>
</tr>
</table>
<P>
says to just index the document's title, but don't index its contents, and
don't follow any links within the document. Granted, it's unlikely that
this feature will ever be used...
<P>
If you are indexing your own site, and know what you are doing, you can
disable robot exclusion by the <A HREF="#item_ignore_robots_file">ignore_robots_file</A> configuration parameter, described below. This disables both <EM>robots.txt</EM> and the meta tag parsing. You may disable just the meta tag parsing by
using <CODE>ignore_robots_headers</CODE>.
<P>
This script only spiders one file at a time, so load on the web server is
not that great. And with libwww-perl-5.53_91 HTTP/1.1 keep alive requests
can reduce the load on the server even more (and potentially reduce
spidering time considerably).
<P>
Still, discuss spidering with a site's administrator before beginning. Use
the <A HREF="#item_delay_sec">delay_sec</A> to adjust how fast the spider fetches documents. Consider running a second
web server with a limited number of children if you really want to fine
tune the resources used by spidering.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="Duplicate_Documents">Duplicate Documents</A></H2>
<P>
The spider program keeps track of URLs visited, so a document is only
indexed one time.
<P>
The Digest::MD5 module can be used to create a "fingerprint" of
every page indexed and this fingerprint is used in a hash to find duplicate
pages. For example, MD5 will prevent indexing these as two different
documents:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://localhost/path/to/some/index.html">http://localhost/path/to/some/index.html</A>
<A HREF="http://localhost/path/to/some/">http://localhost/path/to/some/</A></pre>
</td>
</tr>
</table>
<P>
But note that this may have side effects you don't want. If you want this
file indexed under this URL:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://localhost/important.html">http://localhost/important.html</A></pre>
</td>
</tr>
</table>
<P>
But the spider happens to find the exact content in this file first:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://localhost/developement/test/todo/maybeimportant.html">http://localhost/developement/test/todo/maybeimportant.html</A></pre>
</td>
</tr>
</table>
<P>
Then only that URL will be indexed.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="Broken_relative_links">Broken relative links</A></H2>
<P>
Sometimes web page authors use too many <CODE>/../</CODE> segments in relative URLs which reference documents above the document
root. Some web servers such as Apache will return a 400 Bad Request when
requesting a document above the root. Other web servers such as Micorsoft
IIS/5.0 will try and "correct" these errors. This correction will
lead to loops when spidering.
<P>
The spider can fix these above-root links by placing the following in your
spider config:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> remove_leading_dots => 1,</pre>
</td>
</tr>
</table>
<P>
It is not on by default so that the spider can report the broken links (as
400 errors on sane webservers).
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="Compression">Compression</A></H2>
<P>
If The Perl module Compress::Zlib is installed the spider will send the
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> Accept-Encoding: gzip</pre>
</td>
</tr>
</table>
<P>
header and uncompress the document if the server returns the header
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> Content-Encoding: gzip</pre>
</td>
</tr>
</table>
<P>
MD5 checksomes are done on the compressed data.
<P>
MD5 may slow down indexing a tiny bit, so test with and without if speed is
an issue (which it probably isn't since you are spidering in the first
place). This feature will also use more memory.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="REQUIREMENTS">REQUIREMENTS</A></H1>
<P>
Perl 5 (hopefully at least 5.00503) or later.
<P>
You must have the LWP Bundle on your computer. Load the LWP::Bundle via the
CPAN.pm shell, or download libwww-perl-x.xx from CPAN (or via ActiveState's
ppm utility). Also required is the the HTML-Parser-x.xx bundle of modules
also from CPAN (and from ActiveState for Windows).
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://search.cpan.org/search?dist=libwww-perl">http://search.cpan.org/search?dist=libwww-perl</A>
<A HREF="http://search.cpan.org/search?dist=HTML-Parser">http://search.cpan.org/search?dist=HTML-Parser</A></pre>
</td>
</tr>
</table>
<P>
You will also need Digest::MD5 if you wish to use the MD5 feature.
HTML::Tagset is also required. Other modules may be required (for example,
the pod2xml.pm module has its own requirementes -- see perldoc pod2xml for
info).
<P>
The spider.pl script, like everyone else, expects perl to live in
/usr/local/bin. If this is not the case then either add a symlink at
/usr/local/bin/perl to point to where perl is installed or modify the
shebang (#!) line at the top of the spider.pl program.
<P>
Note that the libwww-perl package does not support SSL (Secure Sockets
Layer) (https) by default. See <EM>README.SSL</EM> included in the libwww-perl package for information on installing SSL
support.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="CONFIGURATION_FILE">CONFIGURATION FILE</A></H1>
<P>
The spider configuration file is a read by the script as Perl code. This
makes the configuration a bit more complex than simple text config files,
but allows the spider to be configured programmatically.
<P>
For example, the config file can contain logic for testing URLs against
regular expressions or even against a database lookup while running.
<P>
The configuration file sets an array called <CODE>@servers</CODE>. This array can contain one or more hash structures of parameters. Each
hash structure is a configuration for a single server.
<P>
Here's an example:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %main_site = (
base_url => '<A HREF="http://example.com">http://example.com</A>',
same_hosts => 'www.example.com',
email => 'admin@example.com',
);</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %news_site = (
base_url => '<A HREF="http://news.example.com">http://news.example.com</A>',
email => 'admin@example.com',
);</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> @servers = ( \%main_site, \%news_site );
1;</pre>
</td>
</tr>
</table>
<P>
The above defines two Perl hashes (%main_site and %news_site) and then
places a *reference* (the backslash before the name of the hash) to each of
those hashes in the <CODE>@servers</CODE> array. The "1;" at the
end is required at the end of the file (Perl must see a true value at the
end of the file).
<P>
The <CODE>config file path</CODE> is the first parameter passed to the spider script.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl F<config></pre>
</td>
</tr>
</table>
<P>
If you do not specify a config file then the spider will look for the file
<EM>SwishSpiderConfig.pl</EM> in the current directory.
<P>
The Swish-e distribution includes a <EM>SwishSpiderConfig.pl</EM> file with a few example configurations. This example file is installed in
the <EM>prog-bin/</EM>
documentation directory (on unix often this is
/usr/local/share/swish-e/prog-bin).
<P>
When the special config file name "default" is used:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> SwishProgParameters default <A HREF="http://www.mysite/index.html">http://www.mysite/index.html</A> [<URL>] [...]</pre>
</td>
</tr>
</table>
<P>
Then a default set of parameters are used with the spider. This is a good
way to start using the spider before attempting to create a configuration
file.
<P>
The default settings skip any urls that look like images (well, .gif .jpeg
.png), and attempts to filter PDF and MS Word documents IF you have the
required filter programs installed (which are not part of the Swish-e
distribution). The spider will follow "a" and "frame"
type of links only.
<P>
Note that if you do use a spider configuration file that the default
configuration will NOT be used (unless you set the
"use_default_config" option in your config file).
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="CONFIGURATION_OPTIONS">CONFIGURATION OPTIONS</A></H1>
<P>
This describes the required and optional keys in the server configuration
hash, in random order...
<DL>
<P><DT><STRONG><A NAME="item_base_url">base_url</A></STRONG><DD>
<P>
This required setting is the starting URL for spidering.
<P>
This sets the first URL the spider will fetch. It does NOT limit spidering
to URLs at or below the level of the directory specified in this setting.
For that feature you need to use the <A HREF="#item_test_url">test_url</A> callback function.
<P>
Typically, you will just list one URL for the base_url. You may specify
more than one URL as a reference to a list and each will be spidered:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> base_url => [qw! <A HREF="http://swish-e.org/">http://swish-e.org/</A> <A HREF="http://othersite.org/other/index.html">http://othersite.org/other/index.html</A> !],</pre>
</td>
</tr>
</table>
<P>
but each site will use the same config opions. If you want to index two
separate sites you will likely rather add an additional configuration to
the <CODE>@servers</CODE> array.
<P>
You may specify a username and password:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> base_url => '<A HREF="http://user:pass@swish-e.org/index.html">http://user:pass@swish-e.org/index.html</A>',</pre>
</td>
</tr>
</table>
<P>
If a URL is protected by Basic Authentication you will be prompted for a
username and password. The parameter <A HREF="#item_max_wait_time">max_wait_time</A> controls how long to wait for user entry before skipping the current URL.
See also <A HREF="#item_credentials">credentials</A>
below.
<P><DT><STRONG><A NAME="item_same_hosts">same_hosts</A></STRONG><DD>
<P>
This optional key sets equivalent <STRONG>authority</STRONG> <CODE>name(s)</CODE> for the site you are spidering. For example, if your
site is <CODE>www.mysite.edu</CODE> but also can be reached by
<CODE>mysite.edu</CODE> (with or without <CODE>www</CODE>) and also <CODE>web.mysite.edu</CODE> then:
<P>
Example:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> $serverA{base_url} = '<A HREF="http://www.mysite.edu/index.html">http://www.mysite.edu/index.html</A>';
$serverA{same_hosts} = ['mysite.edu', 'web.mysite.edu'];</pre>
</td>
</tr>
</table>
<P>
Now, if a link is found while spidering of:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://web.mysite.edu/path/to/file.html">http://web.mysite.edu/path/to/file.html</A></pre>
</td>
</tr>
</table>
<P>
it will be considered on the same site, and will actually spidered and
indexed as:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://www.mysite.edu/path/to/file.html">http://www.mysite.edu/path/to/file.html</A></pre>
</td>
</tr>
</table>
<P>
Note: This should probably be called <STRONG>same_host_port</STRONG> because it compares the URI <CODE>host:port</CODE>
against the list of host names in <A HREF="#item_same_hosts">same_hosts</A>. So, if you specify a port name in you will want to specify the port name
in the the list of hosts in <A HREF="#item_same_hosts">same_hosts</A>:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %serverA = (
base_url => '<A HREF="http://sunsite.berkeley.edu:4444/">http://sunsite.berkeley.edu:4444/</A>',
same_hosts => [ qw/www.sunsite.berkeley.edu:4444/ ],
email => 'my@email.address',
);</pre>
</td>
</tr>
</table>
<P><DT><STRONG><A NAME="item_email">email</A></STRONG><DD>
<P>
This required key sets the email address for the spider. Set this to your
email address.
<P><DT><STRONG><A NAME="item_agent">agent</A></STRONG><DD>
<P>
This optional key sets the name of the spider.
<P><DT><STRONG><A NAME="item_link_tags">link_tags</A></STRONG><DD>
<P>
This optional tag is a reference to an array of tags. Only links found in
these tags will be extracted. The default is to only extract links from >a< tags.
<P>
For example, to extract tags from <CODE>a</CODE> tags and from <CODE>frame</CODE> tags:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %serverA = (
base_url => '<A HREF="http://sunsite.berkeley.edu:4444/">http://sunsite.berkeley.edu:4444/</A>',
same_hosts => [ qw/www.sunsite.berkeley.edu:4444/ ],
email => 'my@email.address',
link_tags => [qw/ a frame /],
);</pre>
</td>
</tr>
</table>
<P><DT><STRONG><A NAME="item_use_default_config">use_default_config</A></STRONG><DD>
<P>
This option is new for Swish-e 2.4.3.
<P>
The spider has a hard-coded default configuration that's available when the
spider is run with the configuration file listed as "default":
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl default <url></pre>
</td>
</tr>
</table>
<P>
This default configuration skips urls that match the regular expression:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> /\.(?:gif|jpeg|png)$/i</pre>
</td>
</tr>
</table>
<P>
and the spider will attempt to use the SWISH::Filter module for filtering
non-text documents. (You still need to install programs to do the actual
filtering, though).
<P>
Here's the basic config for the "default" mode:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> @servers = (
{
email => 'swish@user.failed.to.set.email.invalid',
link_tags => [qw/ a frame /],
keep_alive => 1,
test_url => sub { $_[0]->path !~ /\.(?:gif|jpeg|png)$/i },
test_response => $response_sub,
use_head_requests => 1, # Due to the response sub
filter_content => $filter_sub,
} );</pre>
</td>
</tr>
</table>
<P>
The filter_content callback will be used if SWISH::Filter was loaded and
ready to use. This doesn't mean that filtering will work automatically --
you will likely need to install aditional programs for filtering (like Xpdf
or Catdoc).
<P>
The test_response callback will be set to test if a given content type can
be filtered by SWISH::Filter (if SWISH::Filter was loaded), otherwise, it
will check for content-type of text/* -- any text type of document.
<P>
Normally, if you specify your own config file:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ./spider.pl my_own_spider.config</pre>
</td>
</tr>
</table>
<P>
then you must setup those features available in the default setting in your
own config file. But, if you wish to build upon the "default"
config file then set this option.
<P>
For example, to use the default config but specify your own email address:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> @servers = (
{
email => my@email.address,
use_default_config => 1,
delay_sec => 0,
},
);
1;</pre>
</td>
</tr>
</table>
<P>
What this does is "merge" your config file with the default
config file.
<P><DT><STRONG><A NAME="item_delay_sec">delay_sec</A></STRONG><DD>
<P>
This optional key sets the delay in seconds to wait between requests. See
the LWP::RobotUA man page for more information. The default is 5 seconds.
Set to zero for no delay.
<P>
When using the keep_alive feature (recommended) the delay will be used only
where the previous request returned a "Connection: closed"
header.
<P><DT><STRONG><A NAME="item_delay_min">delay_min (deprecated)</A></STRONG><DD>
<P>
Set the delay to wait between requests in minutes. If both delay_sec and
delay_min are defined, delay_sec will be used.
<P><DT><STRONG><A NAME="item_max_wait_time">max_wait_time</A></STRONG><DD>
<P>
This setting is the number of seconds to wait for data to be returned from
the request. Data is returned in chunks to the spider, and the timer is
reset each time a new chunk is reported. Therefore, documents (requests)
that take longer than this setting should not be aborted as long as some
data is received every max_wait_time seconds. The default it 30 seconds.
<P>
NOTE: This option has no effect on Windows.
<P><DT><STRONG><A NAME="item_max_time">max_time</A></STRONG><DD>
<P>
This optional key will set the max minutes to spider. Spidering for this
host will stop after <A HREF="#item_max_time">max_time</A> minutes, and move on to the next server, if any. The default is to not
limit by time.
<P><DT><STRONG><A NAME="item_max_files">max_files</A></STRONG><DD>
<P>
This optional key sets the max number of files to spider before aborting.
The default is to not limit by number of files. This is the number of
requests made to the remote server, not the total number of files to index
(see <A HREF="#item_max_indexed">max_indexed</A>). This count is displayted at the end of indexing as <CODE>Unique URLs</CODE>.
<P>
This feature can (and perhaps should) be use when spidering a web site
where dynamic content may generate unique URLs to prevent run-away
spidering.
<P><DT><STRONG><A NAME="item_max_indexed">max_indexed</A></STRONG><DD>
<P>
This optional key sets the max number of files that will be indexed. The
default is to not limit. This is the number of files sent to swish for
indexing (and is reported by <CODE>Total Docs</CODE> when spidering ends).
<P><DT><STRONG><A NAME="item_max_size">max_size</A></STRONG><DD>
<P>
This optional key sets the max size of a file read from the web server.
This <STRONG>defaults</STRONG> to 5,000,000 bytes. If the size is exceeded the resource is skipped and a
message is written to STDERR if the DEBUG_SKIPPED debug flag is set.
<P>
Set max_size to zero for unlimited size. If the server returns a
Content-Length header then that will be used. Otherwise, the document will
be checked for size limitation as it arrives. That's a good reason to have
your server send Content-Length headers.
<P>
See also <A HREF="#item_use_head_requests">use_head_requests</A> below.
<P><DT><STRONG><A NAME="item_keep_alive">keep_alive</A></STRONG><DD>
<P>
This optional parameter will enable keep alive requests. This can
dramatically speed up spidering and reduce the load on server being
spidered. The default is to not use keep alives, although enabling it will
probably be the right thing to do.
<P>
To get the most out of keep alives, you may want to set up your web server
to allow a lot of requests per single connection (i.e MaxKeepAliveRequests
on Apache). Apache's default is 100, which should be good.
<P>
When a connection is not closed the spider does not wait the
"delay_sec" time when making the next request. In other words,
there is no delay in requesting documents while the connection is open.
<P>
Note: try to filter as many documents as possible <STRONG>before</STRONG> making the request to the server. In other words, use <A HREF="#item_test_url">test_url</A> to look for files ending in <CODE>.html</CODE> instead of using <A HREF="#item_test_response">test_response</A> to look for a content type of <CODE>text/html</CODE> if possible. Do note that aborting a request from <A HREF="#item_test_response">test_response</A> will break the current keep alive connection.
<P>
Note: you must have at least libwww-perl-5.53_90 installed to use this
feature.
<P><DT><STRONG><A NAME="item_use_head_requests">use_head_requests</A></STRONG><DD>
<P>
This option is new as of swish-e 2.4.3 and can effect the speed of
spidering and the load of the web server.
<P>
To understand this you will likely need to read about the <A HREF="#CALLBACK_FUNCTIONS">CALLBACK FUNCTIONS</A>
below -- specifically about the <A HREF="#item_test_response">test_response</A> callback function. This option is also only used when <A HREF="#item_keep_alive">keep_alive</A> is also enabled (although it could be debated that it's useful without keep
alives).
<P>
This option tells the spider to use http HEAD requests before each request.
<P>
Normally, the spider simply does a GET request and after receiving the
first chunk of data back from the web server calls the <A HREF="#item_test_response">test_response</A> callback function (if one is defined in your config file). The <A HREF="#item_test_response">test_response</A>
callback function is a good place to test the content-type header returned
from the server and reject types that you do not want to index.
<P>
Now, *if* you are using the <A HREF="#item_keep_alive">keep_alive</A> feature then rejecting a document will often (always?) break the keep alive
connection.
<P>
So, what the <A HREF="#item_use_head_requests">use_head_requests</A> option does is issue a HEAD request for every document, checks for a
Content-Length header (to check if the document is larger than
<A HREF="#item_max_size">max_size</A>, and then calls your <A HREF="#item_test_response">test_response</A> callback function. If your callback function returns true then a GET
request is used to fetch the document.
<P>
The idea is that by using HEAD requests instead of GET request a false
return from your <A HREF="#item_test_response">test_response</A> callback function (i.e. rejecting the document) will not break the keep
alive connection.
<P>
Now, don't get too excited about this. Before using this think about the
ratio of rejected documents to accepted documents. If you reject no
documents then using this feature will double the number of requests to the
web server -- which will also double the number of connections to the web
server. But, if you reject a large percentage of documents then this
feature will help maximize the number of keep alive requests to the server
(i.e. reduce the number of separate connections needed).
<P>
There's also another problem with using HEAD requests. Some broken servers
may not respond correctly to HEAD requests (some issues a 500 error), but
respond fine to a normal GET request. This is something to watch out for.
<P>
Finally, if you do not have a <A HREF="#item_test_response">test_response</A> callback AND <A HREF="#item_max_size">max_size</A> is set to zero then setting <A HREF="#item_use_head_requests">use_head_requests</A> will have no effect.
<P>
And, with all other factors involved you might find this option has no
effect at all.
<P><DT><STRONG><A NAME="item_skip">skip</A></STRONG><DD>
<P>
This optional key can be used to skip the current server. It's only purpose
is to make it easy to disable a specific server hash in a configuration
file.
<P><DT><STRONG><A NAME="item_debug">debug</A></STRONG><DD>
<P>
Set this item to a comma-separated list of debugging options.
<P>
Options are currently:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> errors, failed, headers, info, links, redirect, skipped, url</pre>
</td>
</tr>
</table>
<P>
Here are basically the levels:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> errors => general program errors (not used at this time)
url => print out every URL processes
headers => prints the response headers
failed => failed to return a 200
skipped => didn't index for some reason
info => a little more verbose
links => prints links as they are extracted
redirect => prints out redirected URLs</pre>
</td>
</tr>
</table>
<P>
Debugging can be also be set by an environment variable SPIDER_DEBUG when
running <EM>spider.pl</EM>. You can specify any of the above debugging options, separated by a comma.
<P>
For example with Bourne type shell:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> SPIDER_DEBUG=url,links spider.pl [....]</pre>
</td>
</tr>
</table>
<P>
Before Swish-e 2.4.3 you had to use the internal debugging constants or'ed
together like so:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> debug => DEBUG_URL | DEBUG_FAILED | DEBUG_SKIPPED,</pre>
</td>
</tr>
</table>
<P>
You can still do this, but the string version is easier. In fact, if you
want to turn on debugging dynamically (for example in a
<CODE>test_url()</CODE> callback function) then you currently *must* use
the DEBUG_* constants. The string is converted to a number only at the
start of spiderig -- after that the <A HREF="#item_debug">debug</A>
parameter is converted to a number.
<P><DT><STRONG><A NAME="item_quiet">quiet</A></STRONG><DD>
<P>
If this is true then normal, non-error messages will be supressed. Quiet
mode can also be set by setting the environment variable SPIDER_QUIET to
any true value.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> SPIDER_QUIET=1</pre>
</td>
</tr>
</table>
<P><DT><STRONG><A NAME="item_max_depth">max_depth</A></STRONG><DD>
<P>
The <A HREF="#item_max_depth">max_depth</A> parameter can be used to limit how deeply to recurse a web site. The depth
is just a count of levels of web pages decended, and not related to the
number of path elements in a URL.
<P>
A max_depth of zero says to only spider the page listed as the <A HREF="#item_base_url">base_url</A>. A max_depth of one will spider the <A HREF="#item_base_url">base_url</A> page, plus all links on that page, and no more. The default is to spider
all pages.
<P><DT><STRONG><A NAME="item_ignore_robots_file">ignore_robots_file</A></STRONG><DD>
<P>
If this is set to true then the robots.txt file will not be checked when
spidering this server. Don't use this option unless you know what you are
doing.
<P><DT><STRONG><A NAME="item_use_cookies">use_cookies</A></STRONG><DD>
<P>
If this is set then a "cookie jar" will be maintained while
spidering. Some (poorly written ;) sites require cookies to be enabled on
clients.
<P>
This requires the HTTP::Cookies module.
<P><DT><STRONG><A NAME="item_use_md5">use_md5</A></STRONG><DD>
<P>
If this setting is true, then a MD5 digest "fingerprint" will be
made from the content of every spidered document. This digest number will
be used as a hash key to prevent indexing the same content more than once.
This is helpful if different URLs generate the same content.
<P>
Obvious example is these two documents will only be indexed one time:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> <A HREF="http://localhost/path/to/index.html">http://localhost/path/to/index.html</A>
<A HREF="http://localhost/path/to/">http://localhost/path/to/</A></pre>
</td>
</tr>
</table>
<P>
This option requires the Digest::MD5 module. Spidering with this option
might be a tiny bit slower.
<P><DT><STRONG><A NAME="item_validate_links">validate_links</A></STRONG><DD>
<P>
Just a hack. If you set this true the spider will do HEAD requests all
links (e.g. off-site links), just to make sure that all your links work.
<P><DT><STRONG><A NAME="item_credentials">credentials</A></STRONG><DD>
<P>
You may specify a username and password to be used automatically when
spidering:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> credentials => 'username:password',</pre>
</td>
</tr>
</table>
<P>
A username and password supplied in a URL will override this setting. This
username and password will be used for every request.
<P>
See also the <A HREF="#item_get_password">get_password</A> callback function below. <A HREF="#item_get_password">get_password</A>, if defined, will be called when a page requires authorization.
<P><DT><STRONG><A NAME="item_credential_timeout">credential_timeout</A></STRONG><DD>
<P>
Sets the number of seconds to wait for user input when prompted for a
username or password. The default is 30 seconds.
<P>
Set this to zero to wait forever. Probably not a good idea.
<P>
Set to undef to disable asking for a password.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> credential_timeout => undef,</pre>
</td>
</tr>
</table>
<P><DT><STRONG><A NAME="item_remove_leading_dots">remove_leading_dots</A></STRONG><DD>
<P>
Removes leading dots from URLs that might reference documents above the
document root. The default is to not remove the dots.
</DL>
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="CALLBACK_FUNCTIONS">CALLBACK FUNCTIONS</A></H1>
<P>
Callback functions can be defined in your parameter hash. These optional
settings are <EM>callback</EM> subroutines that are called while processing URLs.
<P>
A little perl discussion is in order:
<P>
In perl, a scalar variable can contain a reference to a subroutine. The
config example above shows that the configuration parameters are stored in
a perl <EM>hash</EM>.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %serverA = (
base_url => '<A HREF="http://sunsite.berkeley.edu:4444/">http://sunsite.berkeley.edu:4444/</A>',
same_hosts => [ qw/www.sunsite.berkeley.edu:4444/ ],
email => 'my@email.address',
link_tags => [qw/ a frame /],
);</pre>
</td>
</tr>
</table>
<P>
There's two ways to add a reference to a subroutine to this hash:
<P>
sub foo { return 1; }
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %serverA = (
base_url => '<A HREF="http://sunsite.berkeley.edu:4444/">http://sunsite.berkeley.edu:4444/</A>',
same_hosts => [ qw/www.sunsite.berkeley.edu:4444/ ],
email => 'my@email.address',
link_tags => [qw/ a frame /],
test_url => \&foo, # a reference to a named subroutine
);</pre>
</td>
</tr>
</table>
<P>
Or the subroutine can be coded right in place:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my %serverA = (
base_url => '<A HREF="http://sunsite.berkeley.edu:4444/">http://sunsite.berkeley.edu:4444/</A>',
same_hosts => [ qw/www.sunsite.berkeley.edu:4444/ ],
email => 'my@email.address',
link_tags => [qw/ a frame /],
test_url => sub { reutrn 1; },
);</pre>
</td>
</tr>
</table>
<P>
The above example is not very useful as it just creates a user callback
function that always returns a true value (the number 1). But, it's just an
example.
<P>
The function calls are wrapped in an eval, so calling die (or doing
something that dies) will just cause that URL to be skipped. If you really
want to stop processing you need to set $server->{abort} in your
subroutine (or send a kill -HUP to the spider).
<P>
The first two parameters passed are a URI object (to have access to the
current URL), and a reference to the current server hash. The <CODE>server</CODE> hash is just a global hash for holding data, and useful for setting flags
as described below.
<P>
Other parameters may be also passed in depending the the callback function,
as described below. In perl parameters are passed in an array called
"@_". The first element (first parameter) of that array is $_[0],
and the second is $_[1], and so on. Depending on how complicated your
function is you may wish to shift your parameters off of the
<CODE>@_</CODE> list to make working with them easier. See the examples
below.
<P>
To make use of these routines you need to understand when they are called,
and what changes you can make in your routines. Each routine deals with a
given step, and returning false from your routine will stop processing for
the current URL.
<DL>
<P><DT><STRONG><A NAME="item_test_url">test_url</A></STRONG><DD>
<P>
<A HREF="#item_test_url">test_url</A> allows you to skip processing of urls based on the url before the request
to the server is made. This function is called for the <A HREF="#item_base_url">base_url</A> links (links you define in the spider configuration file) and for every
link extracted from a fetched web page.
<P>
This function is a good place to skip links that you are not interested in
following. For example, if you know there's no point in requesting images
then you can exclude them like:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_url => sub {
my $uri = shift;
return 0 if $uri->path =~ /\.(gif|jpeg|png)$/;
return 1;
},</pre>
</td>
</tr>
</table>
<P>
Or to write it another way:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_url => sub { $_[0]->path !~ /\.(gif|jpeg|png)$/ },</pre>
</td>
</tr>
</table>
<P>
Another feature would be if you were using a web server where path names
are NOT case sensitive (e.g. Windows). You can normalize all links in this
situation using something like
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_url => sub {
my $uri = shift;
return 0 if $uri->path =~ /\.(gif|jpeg|png)$/;</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> $uri->path( lc $uri->path ); # make all path names lowercase
return 1;
},</pre>
</td>
</tr>
</table>
<P>
The important thing about <A HREF="#item_test_url">test_url</A> (compared to the other callback functions) is that it is called while <EM>extracting</EM> links, not while actually fetching that page from the web server. Returning
false from <A HREF="#item_test_url">test_url</A> simple says to not add the URL to the list of links to spider.
<P>
You may set a flag in the server hash (second parameter) to tell the spider
to abort processing.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_url => sub {
my $server = $_[1];
$server->{abort}++ if $_[0]->path =~ /foo\.html/;
return 1;
},</pre>
</td>
</tr>
</table>
<P>
You cannot use the server flags:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> no_contents
no_index
no_spider</pre>
</td>
</tr>
</table>
<P>
This is discussed below.
<P><DT><STRONG><A NAME="item_test_response">test_response</A></STRONG><DD>
<P>
This function allows you to filter based on the response from the remote
server (such as by content-type).
<P>
Web servers use a Content-Type: header to define the type of data returned
from the server. On a web server you could have a .jpeg file be a web page
-- file extensions may not always indicate the type of the file.
<P>
If you enable <A HREF="#item_use_head_requests">use_head_requests</A> then this function is called after the spider makes a HEAD request.
Otherwise, this function is called while the web pages is being fetched
from the remote server, typically after just enought data has been returned
to read the response from the web server.
<P>
The test_response callback function is called with the following
parameters:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ( $uri, $server, $response, $content_chunk )</pre>
</td>
</tr>
</table>
<P>
The <CODE>$response</CODE> variable is a HTTP::Response object and provies
methods of examining the server's response. The <CODE>$content_chunk</CODE>
is the first chunk of data returned from the server (if not a HEAD
request).
<P>
When not using <A HREF="#item_use_head_requests">use_head_requests</A> the spider requests a document in "chunks" of 4096 bytes. 4096 is
only a suggestion of how many bytes to return in each chunk. The <A HREF="#item_test_response">test_response</A> routine is called when the first chunk is received only. This allows
ignoring (aborting) reading of a very large file, for example, without
having to read the entire file. Although not much use, a reference to this
chunk is passed as the forth parameter.
<P>
If you are spidering a site with many different types of content that you
do not wish to index (and cannot use a test_url callback to determine what
docs to skip) then you will see better performance using both the <A HREF="#item_use_head_requests">use_head_requests</A> and <A HREF="#item_keep_alive">keep_alive</A>
features. (Aborting a GET request kills the keep-alive session.)
<P>
For example, to only index true HTML (text/html) pages:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_response => sub {
my $content_type = $_[2]->content_type;
return $content_type =~ m!text/html!;
},</pre>
</td>
</tr>
</table>
<P>
You can also set flags in the server hash (the second parameter) to control
indexing:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> no_contents -- index only the title (or file name), and not the contents
no_index -- do not index this file, but continue to spider if HTML
no_spider -- index, but do not spider this file for links to follow
abort -- stop spidering any more files</pre>
</td>
</tr>
</table>
<P>
For example, to avoid index the contents of "private.html", yet
still follow any links in that file:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_response => sub {
my $server = $_[1];
$server->{no_index}++ if $_[0]->path =~ /private\.html$/;
return 1;
},</pre>
</td>
</tr>
</table>
<P>
Note: Do not modify the URI object in this call back function.
<P><DT><STRONG><A NAME="item_filter_content">filter_content</A></STRONG><DD>
<P>
This callback function is called right before sending the content to swish.
Like the other callback function, returning false will cause the URL to be
skipped. Setting the <CODE>abort</CODE> server flag and returning false will abort spidering.
<P>
You can also set the <CODE>no_contents</CODE> flag.
<P>
This callback function is passed four parameters. The URI object, server
hash, the HTTP::Response object, and a reference to the content.
<P>
You can modify the content as needed. For example you might not like upper
case:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> filter_content => sub {
my $content_ref = $_[3];</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> $$content_ref = lc $$content_ref;
return 1;
},</pre>
</td>
</tr>
</table>
<P>
I more reasonable example would be converting PDF or MS Word documents for
parsing by swish. Examples of this are provided in the <EM>prog-bin</EM> directory of the swish-e distribution.
<P>
You may also modify the URI object to change the path name passed to swish
for indexing.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> filter_content => sub {
my $uri = $_[0];
$uri->host('www.other.host') ;
return 1;
},</pre>
</td>
</tr>
</table>
<P>
Swish-e's ReplaceRules feature can also be used for modifying the path name
indexed.
<P>
Note: Swish-e now includes a method of filtering based on the SWISH::Filter
Perl modules. See the SwishSpiderConfig.pl file for an example how to use
SWISH::Filter in a filter_content callback function.
<P>
If you use the "default" configuration (i.e. pass
"default" as the first parameter to the spider) then
SWISH::Filter is used automatically. This only adds code for calling the
programs to filter your content -- you still need to install applications
that do the hard work (like xpdf for pdf conversion and catdoc for MS Word
conversion).
<P>
The a function included in the <EM>spider.pl</EM> for calling SWISH::Filter when using the "default" config can
also be used in your config file. There's a function called
<CODE>swish_filter()</CODE> that returns a list of two subroutines. So in
your config you could do:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> my ($filter_sub, $response_sub ) = swish_filter();</pre>
</td>
</tr>
</table>
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> @server = ( {
test_response => $response_sub,
filter_content => $filter_sub,
[...],
} );</pre>
</td>
</tr>
</table>
<P>
The <CODE>$response_sub</CODE> is not required, but is useful if using HEAD
requests (<A HREF="#item_use_head_requests">use_head_requests</A>): It tests the content type from the server to see if there's any filters
that can handle the document. The <CODE>$filter_sub</CODE> does all the
work of filtering a document.
<P>
Make sense? If not, then that's what the Swish-e list is for.
<P><DT><STRONG><A NAME="item_spider_done">spider_done</A></STRONG><DD>
<P>
This callback is called after processing a server (after each server listed
in the <CODE>@servers</CODE> array if more than one).
<P>
This allows your config file to do any cleanup work after processing. For
example, if you were keeping counts during, say, a
<CODE>test_response()</CODE> callback function you could use the
<CODE>spider_done()</CODE> callback to print the results.
<P><DT><STRONG><A NAME="item_output_function">output_function</A></STRONG><DD>
<P>
If defined, this callback function is called instead of printing the
content and header to STDOUT. This can be used if you want to store the
output of the spider before indexing.
<P>
The output_function is called with the following parameters:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> ($server, $content, $uri, $response, $bytecount, $path);</pre>
</td>
</tr>
</table>
<P>
Here is an example that simply shows two of the params passed:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> output_function => sub {
my ($server, $content, $uri, $response, $bytecount, $path) = @_;
print STDERR "passed: uri $uri, bytecount $bytecount...\n";
# no output to STDOUT for swish-e
}</pre>
</td>
</tr>
</table>
<P>
You can do almost the same thing with a filter_content callback.
<P><DT><STRONG><A NAME="item_get_password">get_password</A></STRONG><DD>
<P>
This callback is called when a HTTP password is needed (i.e. after the
server returns a 401 error). The function can test the URI and Realm and
then return a username and password separated by a colon:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> get_password => sub {
my ( $uri, $server, $response, $realm ) = @_;
if ( $uri->path =~ m!^/path/to/protected! && $realm eq 'private' ) {
return 'joe:secret931password';
}
return; # sorry, I don't know the password.
},</pre>
</td>
</tr>
</table>
<P>
Use the <A HREF="#item_credentials">credentials</A> setting if you know the username and password and they will be the same for
every request. That is, for a site-wide password.
</DL>
<P>
Note that you can create your own counters to display in the summary list
when spidering is finished by adding a value to the hash pointed to by <CODE>$server-</CODE>{counts}>.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_url => sub {
my $server = $_[1];
$server->{no_index}++ if $_[0]->path =~ /private\.html$/;
$server->{counts}{'Private Files'}++;
return 1;
},</pre>
</td>
</tr>
</table>
<P>
Each callback function <STRONG>must</STRONG> return true to continue processing the URL. Returning false will cause
processing of <EM>the current</EM> URL to be skipped.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="More_on_setting_flags">More on setting flags</A></H2>
<P>
Swish (not this spider) has a configuration directive <A HREF="#item_NoContents">NoContents</A> that will instruct swish to index only the title (or file name), and not
the contents. This is often used when indexing binary files such as image
files, but can also be used with html files to index only the document
titles.
<P>
As shown above, you can turn this feature on for specific documents by
setting a flag in the server hash passed into the <A HREF="#item_test_response">test_response</A> or <A HREF="#item_filter_content">filter_content</A> subroutines. For example, in your configuration file you might have the <A HREF="#item_test_response">test_response</A> callback set as:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> test_response => sub {
my ( $uri, $server, $response ) = @_;
# tell swish not to index the contents if this is of type image
$server->{no_contents} = $response->content_type =~ m[^image/];
return 1; # ok to index and spider this document
}</pre>
</td>
</tr>
</table>
<P>
The entire contents of the resource is still read from the web server, and
passed on to swish, but swish will also be passed a <A HREF="#item_No_Contents">No-Contents</A> header which tells swish to enable the NoContents feature for this document
only.
<P>
Note: Swish will index the path name only when <A HREF="#item_NoContents">NoContents</A> is set, unless the document's type (as set by the swish configuration
settings <A HREF="#item_IndexContents">IndexContents</A> or <A HREF="#item_DefaultContents">DefaultContents</A>) is HTML <EM>and</EM> a title is found in the html document.
<P>
Note: In most cases you probably would not want to send a large binary file
to swish, just to be ignored. Therefore, it would be smart to use a <A HREF="#item_filter_content">filter_content</A> callback routine to replace the contents with single character (you cannot
use the empty string at this time).
<P>
A similar flag may be set to prevent indexing a document at all, but still
allow spidering. In general, if you want completely skip spidering a file
you return false from one of the callback routines (<A HREF="#item_test_url">test_url</A>, <A HREF="#item_test_response">test_response</A>, or <A HREF="#item_filter_content">filter_content</A>). Returning false from any of those three callbacks will stop processing
of that file, and the file will <STRONG>not</STRONG> be spidered.
<P>
But there may be some cases where you still want to spider (extract links)
yet, not index the file. An example might be where you wish to index only
PDF files, but you still need to spider all HTML files to find the links to
the PDF files.
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> $server{test_response} = sub {
my ( $uri, $server, $response ) = @_;
$server->{no_index} = $response->content_type ne 'application/pdf';
return 1; # ok to spider, but don't index
}</pre>
</td>
</tr>
</table>
<P>
So, the difference between <CODE>no_contents</CODE> and <CODE>no_index</CODE> is that <CODE>no_contents</CODE> will still index the file name, just not the contents. <CODE>no_index</CODE> will still spider the file (if it's <CODE>text/html</CODE>) but the file will not be processed by swish at all.
<P>
<STRONG>Note:</STRONG> If <CODE>no_index</CODE> is set in a <A HREF="#item_test_response">test_response</A> callback function then the document <EM>will not be filtered</EM>. That is, your <A HREF="#item_filter_content">filter_content</A>
callback function will not be called.
<P>
The <CODE>no_spider</CODE> flag can be set to avoid spiderering an HTML file. The file will still be
indexed unless
<CODE>no_index</CODE> is also set. But if you do not want to index and spider, then simply return
false from one of the three callback funtions.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="SIGNALS">SIGNALS</A></H1>
<P>
Sending a SIGHUP to the running spider will cause it to stop spidering.
This is a good way to abort spidering, but let swish index the documents
retrieved so far.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="CHANGES">CHANGES</A></H1>
<P>
List of some of the changes
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H2><A NAME="Thu_Sep_30_2004_changes_for_Swish_e_2_4_3">Thu Sep 30 2004 - changes for Swish-e 2.4.3</A></H2>
<P>
Code reorganization and a few new featues. Updated docs a little tiny bit.
Introduced a few spelling mistakes.
<DL>
<P><DT><STRONG><A NAME="item_Config">Config opiton: use_default_config</A></STRONG><DD>
<P>
It used to be that you could run the spider like:
<P>
<table>
<tr>
<td bgcolor="#eeeeee" width="1">
</td>
<td>
<pre> spider.pl default <some url></pre>
</td>
</tr>
</table>
<P>
and the spider would use its own internal config. But if you used your own
config file then the defaults were not used. This options allows you to
merge your config with the default config. Makes making small changes to
the default easy.
<P><DT><STRONG>Config option: use_head_requests</STRONG><DD>
<P>
Tells the spider to make a HEAD request before GET'ing the document from
the web server. Useful if you use keep_alive and have a
<CODE>test_response()</CODE> callback that rejects many documents (which
breaks the connection).
<P><DT><STRONG>Config option: spider_done</STRONG><DD>
<P>
Callback to tell you (or tell your config as it may be) that the spider is
done. Useful if you need to do some extra processing when done spidering --
like record counts to a file.
<P><DT><STRONG>Config option: get_password</STRONG><DD>
<P>
This callback is called when a document returns a 401 error needing a
username and password. Useful if spidering a site proteced with multiple
passwords.
<P><DT><STRONG>Config option: output_function</STRONG><DD>
<P>
If defined spider.pl calls this instead of sending ouptut to STDOUT.
<P><DT><STRONG>Config option: debug</STRONG><DD>
<P>
Now you can use the words instead of or'ing the DEBUG_* constants together.
</DL>
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="TODO">TODO</A></H1>
<P>
Add a "get_document" callback that is called right before making
the "GET" request. This would make it easier to use cached
documents. You can do that now in a test_url callback or in a test_response
when using HEAD request.
<P>
Save state of the spider on SIGHUP so spidering could be restored at a
later date.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="COPYRIGHT">COPYRIGHT</A></H1>
<P>
Copyright 2001 Bill Moseley
<P>
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
<P>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
<H1><A NAME="SUPPORT">SUPPORT</A></H1>
<P>
Send all questions to the The SWISH-E discussion list.
<P>
See <A
HREF="http://sunsite.berkeley.edu/SWISH-E.">http://sunsite.berkeley.edu/SWISH-E.</A>
[ <B><FONT SIZE=-1><A HREF="#toc">TOC</A></FONT></B> ]
<HR>
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<div class="footer">
<BR>SWISH-E is distributed with <B>no warranty</B> under the terms of the
<A HREF="http://www.fsf.org/copyleft/gpl.html">GNU Public License</A>,<BR>
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