How to Index Anything
You might want to build custom indices of documents for many reasons. A widely cited one is to supply search functionality to a web site, but you also may want to index your e-mail or technical documents. Anyone who has looked into implementing such a functionality has probably found it's not as easy as it might seem. Various factors conspire to make searching difficult.
The venerable and indispensable grep and its ilk are effective for scanning through lines of text. But grep, egrep and their relations won't do everything for you. They won't search across lines, they won't show search results in a ranked order and their linear search algorithms don't lend themselves to searching larger volumes of data.
HTML doesn't help the situation either. Its display-oriented features, idiosyncratic grammar and bevy of formatting and entity tags make it fairly difficult to parse correctly.
At the other end of the data storage spectrum is data slotted into a database. The ubiquitous example is that of the SQL database, which allows somewhat sophisticated search facilities but usually is not particularly fast for searching. Some database engines, notably MySQL 4, address this issue by allowing fast and ranked searches, but they may not be as customizable as desired.
In this article, we explore ways to create custom indices using SWISH-E, Perl and XML on Linux. Through examples, we show how SWISH-E can be used to build indices of HTML files, PDF files and man pages.
SWISH-E (simple web indexing system for humans—enhanced) is a descendant of SWISH, which was created in 1994 by Kevin Hughes. SWISH was transferred in 1996 to the UC Berkeley Library to fix bugs and add features, and the result was licensed under the GPL and renamed SWISH-E. Development continues, spearheaded by current project maintainer Bill Moseley and assisted by a team of developers.
Here at SkateboardDirectory.com, we happened upon SWISH-E when researching indexing toolkits. We found that it offers a unique combination of features that make it attractive for our purposes. Not only does SWISH-E offer a fast and robust toolkit with which to build and query indices, but it is also well documented, undergoes active development and bug fixes and includes a Perl interface. We also liked that maintainer Moseley and other experienced SWISH-E users and developers are usually prompt when addressing questions and bugs brought up on the SWISH-E mailing list.
For our examples, we started with a stock Red Hat 7.3 workstation with the Software Development bundle of packages installed. We also tested the examples on a Red Hat 6.2 workstation and a Debian Woody.
Currently, installing SWISH-E on Red Hat means installing from source, and the zlib and libxml2 libraries are required to build SWISH-E fully. If you find you need to install either, you probably can find packages provided with your distribution. We also use the xpdf package in our examples, so you may want to install that now if it isn't already. Our reference Red Hat 7.3 workstation setup had all of SWISH-E's prerequisites installed.
Here, we describe the use of SWISH-E 2.4, which according to the development team, should be released by the time you read this article. You can fetch and set up SWISH-E with the following sequence of commands, substituting the current version for (x.x):
% wget \ http://swish-e.org/Download/swish-e-x.x.tar.gz % tar zxf swish-e-x.x.tar.gz % cd swish-e-x.x % ./configure % make % make test
To install the SWISH-E binary, C libraries and man pages into their default locations in /usr/local, type make install as root. This installs the SWISH-E executable into /usr/local/bin. If this directory isn't in your PATH, either change your appropriate dot file to include /usr/local/bin in your PATH, or always call the swish-e executable by full pathname, like /usr/local/bin/swish-e.
Now, let's build and install the SWISH::API Perl module from the Perl directory in the source. We'll need it later when we build a Perl client for our index of man pages. SWISH::API is set up by the normal Perl module install process:
% cd perl % perl Makefile.PL % make % make test
Then, install the SWISH-E Perl module by typing make install as root.
Now that SWISH-E and the SWISH::API Perl module are installed fully, let's build a simple index of HTML files to test SWISH-E. For this example, we index the HTML, one-page-per-section versions of the Linux Documentation Project (LDP) HOWTOs, which we've unpacked into ~/HOWTO-htmls/. The tarballs of LDP documents used in this article come from www.tldp.org/docs.html.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide