The Webslave's Handbook

Perl

why Perl?
Perl's lineage and Larry Wall
interpreted vs. compiled
modules
getting started in Perl

the shebang line and which
naming your programs
executable mode
tabs and line breaks
procedural syntax with ;
comments
program flow with exit
variables
- scalar variables
- arrays
using library files with require
error handling with || die
the -w switch
using CGI

file handling commands

manipulating strings

using templates with 1:1 replaces
using templates with xml knockoff markup
pattern matching and sed
substrings

talking to the system

the system command
using ticks to capture standard output
using shell commands (cat, ls, mkdir, etc...)
modularizing your program (also see: subroutines)

loops and conditionals

loop theory - the assembly line
parentheses vs. brackets
while Loops - reading files ( the .= notation) and testing conditions
chomp and $_
looping through an array with foreach $element (@array)
Conditional Operators
If statements
Else and elsif statements
program flow with next and last
incrementing or decrementing a variable

subroutines

When to Use Subroutines
writing a subroutine
calling a subroutine
passing variables to a subroutine and back

sending email from Perl

set path to mail program
open the mail program and pipe data to it, handling error with dienice
prepare the mail header (To:, From:, Subject:, \n\n to close header etc...)
construct the body
close the data stream by closing MAIL filehandle
sending HMTL email

MySQL

Why a Database?
Why MySQL?
MySQL inside perl
Getting Started in MySQL

basic admin
Perl DBI:MySQL
connecting to your database
creating, preparing, and executing SQL statements
data types including varchar and int
self-incrementing columns
null vs. not null
the blob types
creating tables at the command line
altering tables (adding and removing columns)
deleting tables (deleting all contents vs. removing the table definition)
showing and describing tables

Down to business with simple SQL (Structured Query Language)

SELECT

simple SELECT query and FROM
talking between tables - using SELECT qualified by WHERE
compound WHERE qualifier
further qualifying SELECT with ORDER BY()
compound ORDER BY()
determining data size with length()
looping through returned records with while and fetchrow_array()
get MySQL standard datetime with SELECT NOW()

INSERT
UPDATE
DELETE

Introduction

There Are No Webmasters

When the web was being born in the 1990s, the people birthing it seized on the opportunity to establish a standard by which their own jobs would be titled. In the excitement of the moment all humility was forgotten and the term "webmaster" was chosen. Now web developers and administrators are saddled with a mighty moniker to live up to... but is it possible?

Not long after "webmaster" became common a sly rebuttle started floating around the net... "there are no webmasters". This was obviously from webmasters themselves, humility now remembered. It seemed the act of building and running a website was not so simple as it seemed, and true mastery of the medium in all its facets was something few could claim. In addition, the sheer hours invested in keeping the sites alive gave some the sense that the web was a beast growing out of control... something not so much to be mastered, but at a minimum, tamed.

Developing for the web can be a complex undertaking because of the many technologies involved. Each problem or task can suggest several different possible avenues for solution, making use of multiple programming languages or syntaxes that require a working knowledge. Not an evening's worth of labor. Reading this now, you have probably already realized the challenge ahead of you. The more time you are willing to invest, the more you will feel like a master. Let's start learning how to tame the web.

Master of None

Ever heard the expression "Jack of all trades, master of none"? This is what a webmaster needs to be. Many skills are required to build a website, and if you were to become a legitimate expert in each before making a site, you'd have to wait ten years.

That's why we need to take the pressure off a bit. You'll be learning lots of new things, each of which falls into a separate category, and you'll build your knowledge of each incrementally as you go. Over time you will become a Jack of all trades, with various tools in your belt, handy in various situations. Don't worry about becoming a master... there are no webmasters... a broad range of understanding will serve you best in the web environment.

Scope of this Book

In this book I share with you the tools I have managed to add to my own toolbelt over the past 5 years. They are by no means the full set of tools available to you as a web developer. The main topics covered here are HTML, CSS, Javascript, Perl and MySQL. There are a host of other languages to choose from when writing more complex applications for the web. But the concepts covered in this book should provide you solid options in the course of your development. I have chosen Perl/MySQL for my independent web projects because they are essentielly free technologies for the small operation, and also because they offer a somewhat lower learning threshold than, for instance, using full object oriented design with Java or C++.

A Thin Veil

As you might suspect, this book is going to talk a great deal about that dreaded word.... code. Most computer users, myself included, start off intimidated by that word. All the code you ever see looks foreign and cryptic, how can you ever understand it? Why in the world would you want to?

Code lies beneath everything you've ever seen or done on a computer. Millions and millions of lines of code. When you realize what an immense task programming can be, and all the intricacies behind what has been done, it is staggering the work that has gone into delivering us the functionality we enjoy on personal computers today.

The images you see on your screen are but a thin veil between you, the user, and a whole lot of code. That's why when things go awry on your computer, you are so likely to encounter a mind-boggling error message referring to a fatal error on line #237 or something. The code has failed to handle some event and is trying to tell you about it.... as though you were the developer and could do something about it.

But when when you are the developer line #237 might well mean something to you. You would open your program and examine that line, looking for bad syntax or other such gremlins. Hopefully you'll be able to go "beneath the veil" after reading this book, and actually speak some of the languages of the web enough to recognize what you see under there.

Basic Web Architecture

Uniform Resource Locators (URLs)

They sound fancy but they're not: they're simply the way we find things on the web. They are the addresses that begin with http:// and eventually end in some file name or some other fancy looking string of characters. A URL can begin with an IP address...

http://216.239.51.100

...or, more commonly, a domain name:

http://www.google.com

In this case, both URLs will get you to the same place, because 216.239.51.100 is the IP address for google.com. The association of domain names to IP addresses is made by DNS (Domain Name Servers) so that we can all enjoy easy to remember names for our websites instead of digits.

HTTP stands for Hypertext Transfer Protocol, the kind of communication a webserver listens for.

Webservers

A webserver is software which listens for incoming http requests and responds by transfering the requested files (and associated files) over the network to the web browser. There are many makes of webserver software but by far the most popular is Apache, which runs on UNIX and Linux operating systems. This book does not cover webserver administration, but it does recommend Apache when choosing webhosts.

Webhosts

A webhost is the best friend of a webmaster. Webhosts are businesses which provide all your basic webserver resources at a monthly fee in order for you to get your site on the world wide web. They take care of all the nasty details involved in configuring the webserver software, installing other software, partitioning their disk space, etc, etc... things you would have to do instead of working on your website. The services of these companies (the good ones) are worth every penny and it is highly recommended that you begin any website venture by outsourcing you webhosting in this way. Unless you are a major corporation, or just really into hosting your own site at home, get your site hosted by a reputable service provider. They will help you register your domain name and take care of the DNS details mentioned above that you won't want to deal with on your own.

Browsers

You have never seen a webpage as intended but through a piece of software known as a browser. It is the client portion of the client-server relationship for which we have already discussed the server portion. Just as there are many varieties of webserver software, there are many varities of browser software... and a most popular. Microsoft's Internet Explorer is the most popular browser, by far, as of this writing. This is because of the sly practice of tying the browser closely to the desktop operating system, Microsoft Windows, also most popular in its class currently.

But Microsoft is not the only developer of browser software, and those surfing using Netscape or anything in the "Other" category (including Opera and Mozilla, a Netscape offshoot project) represent a significant percentage of your browsership.

What do we care which browsers our surfing audience may be using? Have a seat and brace for some bad news, because this is some of the worst news a developer can get. Browser client applications process code in different ways and often your webpage which looks great in one browser craps out in another. This problem becomes most troublesome when dealing with Javascript, a language which has suffered the worst from attempted standards making and standards breaking of any I have seen.

That's why the most important thing for a web develop to know about browser is that you need to test in more than one. Load one or more (ideally) alternate web browsers on your computer and fully test your website for aesthetics and functionality in each one. The results may disappoint you, and you will have to make a judgement call. Is this aberration acceptable? Can I live with this difference for my [insert browser here] users? If not, you'll need to hit the net or your favorite book to work out the compatibility problem.

In this book I attempt to present only HTML, CSS and Javascript code which is compatible with the two main browsers, Internet Explorer and Netscape. With luck this will help you prevent running into any problems right away. But eventually, the more functionality you develop on the client side, the more you will have to deal with browser compatibility issues.

</bad news> :)

Front End vs. Back End

Don't be gross. This section is about how the developer sees a client-server application like the world wide web. Most web developers start off conceiving of their site as primarily a "front end" object. In other words, all the "action" is on the client side, where the user is viewing the webpage on her browser. You layout the words and images which comprise the main experience of visiting the website. This is essentielly done with HTML and Javascript, as well as other tools like CSS. Your pages in these languages are downloaded to the web browser and processed on the user's computer.

If this is the front end, what is the back? The back is your webserver, and the kicker is, you can elect to do processing there if you like as well. This turns out to be an immensely powerful option with potential to greatly simplify a webmaster's daily tasks. Writing programs for the back end of your website is the Holy Grail of the beginning developer and I hope you will pursue it and know the joys of conquering it.
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On to The Front End

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copyright 2004 Marcus Del Greco