=head1 NAME

SWISH-SEARCH - Swish-e Searching Instructions

=head1 OVERVIEW

This page describes the process of searching with Swish-e.  Please see
the L<SWISH-CONFIG|SWISH-CONFIG> page for information the Swish-e
configuration file directives, and L<SWISH-RUN|SWISH-RUN> for a complete
list of command line arguments.

Searching a Swish-e index involves passing L<command line
arguments|SWISH-RUN> to it that specify the index file to use, and
the L<query|/"Searching Syntax and Operations"> (or search words) to
locate in the index.  Swish-e returns a list of file names (or URLs)
that contain the matched search words.  L<Perl|/"Searching with Perl">
is often used as a front-end to Swish-e such as in CGI applications,
and L<perl modules|/"Perl Modules"> exist to for interfacing with Swish-e.

=head1 Searching Syntax and Operations

The C<-w> command line argument (switch) is used specify the search
query to Swish-e.  When running Swish-e from a shell prompt, be careful
to protect your query from shell metacharacters and shell expansions.
This often means placing single or double quotes around your query.
See L<Searching with Perl> if you plan to use Perl as a front end
to Swish-e.

The following section describes various aspects of searching with Swish-e.

=head2 Boolean Operators

You can use the Boolean operators B<and>, B<or>, or B<not> in searching.
Without these Boolean operators, Swish-e will assume you're B<and>ing
the words together.  The operators are not case sensitive.

[Note: you can change the default to B<or>ing by changing the variable
DEFAULT_RULE in the config.h file and recompiling Swish-e.]

Evaluation takes place from B<left to right> only, although you can use
parentheses to force the order of evaluation.

Examples:

     swish-e -w "smilla or snow" -f myIndex

Retrieves files containing either the words "smilla" or "snow".

     swish-e -w "smilla and snow not sense" -f myIndex 
     swish-e -w "(smilla and snow) and not sense" -f myIndex (same thing)

retrieves first the files that contain both the words "smilla" and
"snow"; then among those the ones that do not contain the word "sense".


=head2 Truncation

The wildcard (*) is available, however it can only be used at the end
of a word: otherwise is is considerd a normal character (i.e. can be
searched for if included in the WordCharacters directive).

     swish-e -w "librarian" -f myIndex

this query only retrieves files which contain the given word.

On the other hand:

     swish-e -w "librarian*" -f myIndex

retrieves "librarians", "librarianship", etc. along with "librarian".

Note that wildcard searches combined with word stemming can lead
to unexpected results.  If stemming is enabled, a search term with a
wildcard will be stemmed internally before searching.  So searching for
C<running*> will actually be a search for C<run*>, so C<running*> would
find C<runway>.  Also, searching for C<runn*> will not find C<running>
as you might expect, since C<running> stems to C<run> in the index,
and thus C<runn*> will not find C<run>.


=head2 Order of Evaluation

Expressions are always evaluated left to right: 

    swish -w "juliet not ophelia and pac" -f myIndex 

retrieves files which contain "juliet" and "pac" but not "ophelia" 

However it is always possible to force the order of evaluation by using
parenthesis.  For example:

    swish-e -w "juliet not (ophelia and pac)" -f myIndex 

retrieves files with "juliet" and containing neither "ophelia" nor "pac".

=head2 Meta Tags

MetaNames are used to represent I<fields> (called I<columns> in a
database) and provide a way to search in only parts of a document.
See L<SWISH-CONFIG|SWISH-CONFIG/"Document Contents Directives"> for
a description of MetaNames, and how they are specified in the source
document.

To limit a search to words found in a meta tag you prefix the keywords
with the name of the meta tag, followed by the equal sign:

    metaname = word
    metaname = (this or that)
    metatname = ( (this or that) or "this phrase" )

It is not necessary to have spaces at either side of the "=", consequently
the following are equivalent:

    swish-e -w "metaName=word"
    swish-e -w "metaName = word" 
    swish-e -w "metaName= word" 

To search on a word that contains a "=", precede the "=" with a "\"
(backslash).

    swish-e -w "test\=3 = x\=4 or y\=5" -f <index.file> 

this query returns the files where the word "x=4" is associated with
the metaName "test=3" or that contains the word "y=5" not associated
with any metaName.

Queries can be also constructed using any of the usual search features,
moreover metaName and plain search can be mixed in a single query.

     swish-e -w "metaName1 = (a1 or a4) not (a3 and a7)" -f index.swish-e

This query will retrieve all the files in which "a1" or "a2" are found
in the META tag "metaName1" and that do not contain the words "a3" and
"a7", where "a3" and "a7" are not associated to any meta name.

=head2 Phrase Searching

To search for a phrase in a document use double-quotes to delimit your
search terms.  (The phrase delimiter is set in src/swish.h.)

You must protect the quotes from the shell.

For example, under Unix:

    swish-e -w '"this is a pharase" or (this and that)'
    swish-e -w 'meta1=("this is a pharase") or (this and that)'

Or under Windows:

    swish-e -w \"this is a pharase\" or (this and that)

You can use the C<-P> switch to set the phrase delimiter character.
See L<SWISH-RUN|SWISH-RUN> for examples.

  
=head2 Context

At times you might not want to search for a word in every part of
your files since you know that the word(s) are present in a particular
tag. The ability to seach according to context greatly increases the
chances that your hits will be relevant, and Swish-e provides a mechanism
to do just that.

The -t option in the search command line allows you to search for words
that exist only in specific HTML tags. Each character in the string
you specify in the argument to this option represents a different tag
in which the word is searched; that is you can use any combinations of
the following characters:

    H means all<HEAD> tags 
    B stands for <BODY> tags 
    t is all <TITLE> tags 
    h is <H1> to <H6> (header) tags 
    e is emphasized tags (this may be <B>, <I>, <EM>, or <STRONG>) 
    c is HTML comment tags (<!-- ... -->)

    # This search will look for files with these two words in their titles only.
    swish-e -w "apples oranges" -t t -f myIndex

    # This search will look for files with these words in comments only.
    swish-e -w "keywords draft release" -t c -f myIndex

    This search will look for words in titles, headers, and emphasized tags.
    swish-e -w "world wide web" -t the -f myIndex

=head1 Searching with Perl

Perl ( http://www.perl.com/ ) is probably the most common programming
language used with Swish-e, especially in CGI interfaces.  Perl makes
searching and parsing results with Swish-e easy, but if not done properly
can leave your server vulnerable to attacks.

When designing your CGI scripts you should carefully screen user input,
and include features such as paged results and a timer to limit time
required for a search to complete.  These are to protect your web site
against a denial of service (DoS) attack.

Included with every distribution of Perl is a document called perlsec --
Perl Security.  I<Please> take time to read and understand that document
before writing CGI scripts in perl.

Type at your shell/command prompt:

    perldoc perlsec

If nothing else, start every CGI program in perl as such:

    #!/usr/local/bin/perl -wT
    use strict;

That alone won't make your script secure, but may help you find insecure
code.

=head2 CGI Danger!

There are many examples of CGI scripts on the Internet.  Many are poorly
written and insecure.  A commonly seen way to execute Swish-e from a
perl CGI script is with a I<piped open>.  For example, it is common to
see this type of C<open()>:

    open(SWISH, "$swish -w $query -f $index|");

This C<open()> gives shell access to the entire Internet!  Often an
attempt is made to strip C<$query> of I<bad> characters.  But, this
often fails since it's hard to guess what every I<bad> character is.
Would you have thought about a null?  A better approach is to only allow
I<in> known safe characters.

Even if you can be sure that any user supplied data is safe, this
I<piped open> still passes the command parameters through the shell.
If nothing else, it's just an extra unnecessary step to running Swish-e.

Therefore, the recommended approach is to fork and exec C<swish-e> directly
without passing through the shell.  This process is described in the
perl man page C<perlipc> under the appropriate heading B<Safe Pipe Opens>.

Type:

    perldoc perlipc

If all this sounds complicated you may wish to use a Perl module that
does all the hard work for you.

=head2 Perl Modules

The Swish-e distribution includes a Perl module called SWISH::API.
SWISH::API provides access to the Swish-e C Library.  

The SWISH::API module is I<not> installed by default.

The SWISH::API module will I<embed> Swish-e into your perl program so that searching does
not require running an external program.  Embedding the Swish-e program into your perl
program results in faster Swish-e searches, especially when running under a 
persistent environment like mod_perl since it avoids the cost of opening the
index file for every request (mod_perl is much also much faster than CGI because it
avoids the need to compile Perl code for every request).

See the README file in the F<perl> directory of the Swish-e distribution for installation 
instructions.  Documentation for the SWISH::API module is available at 
http://swish-e.org and is installed along with other HTML documentation on your computer.

=head1 Document Info

$Id: SWISH-SEARCH.pod,v 1.5 2003/05/15 05:38:30 whmoseley Exp $

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