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CGI/Perl
The lecture notes contained in this packet are based on PERL - How To Program by
Deitel. These notes should only be used in the class room in conjunction with the
author’s book. The only purpose of these notes is to extract the important topics that will
be covered in the CGI/Perl class. The notes are used simply as an outline of the material
that will be covered in the class.
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Introduction
Computer organization, Evolution of Operating Systems, Personal Computing,
Distributed Computing and Client/Server Computing
Client server computing
- users work on workstations
- Information is shared over the network
- file servers ( computers) store programs and data that may be used
by client computers distributed across a network
Structured Programming --- > Object Oriented Programming
History of the Internet and the World Wide Web
From: ArpaNet ( Advanced Research Project Agency ) network
using TCP/IP protocol
TCP – Transmission control Protocol ( to route messages properly
from sender to receiver)
IP – Interconnecting Protocol ( to get the variety of computers to
communicate)
TO: commercial use
The World Wide Web – allows computer users to locate and view, over the
Internet, multimedia-based documents ( Developed in 1990 by Tim Berners-Lee of
CERN ( the European Laboratory for Particle Physics)
The Internet mixes computing and communications technologies. Today’s
applications can be written to communicate among the world’s hundred of millions
of computers.
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Perl with the Common Gateway Interface (CGI)
History: In 1986, Larry Wall ( system programmer for National Security Agency
project) invented a new language aimed to integrate features of the UNIX languages
such as awk ( a report generating language) and sed ( stream editor) with the shell (
UNIX command-line scripting language). He wanted the language to be easy to use – but
at the same time to be powerful.
- Perl, the Practical Extraction and Report Language, grew from a text-processing
language to a powerful general purpose programming language mostly used for system
administration
Perl – a flexible, portable and efficient language
Perl 3 – adopted the GNU General Public License
Perl 4 adopted an Artistic License to attract more users.
Both protect Perl’s free open source nature
Perl 5 – reorganized in a major way to fix shortcomings
Perl is particularly effective with CGI - Common Gateway Interface protocol – - ideal
for the WWW – allows users of the internet to connect to web servers which can
then interact with other applications and pass their output to client applications in
the form of dynamic content.
The event of CGI – transformed Perl from a systems administration tool to
the most widely used - Server Side Internet Programming Language
HTTP
Protocol
CGI
Protocol
CGI/script
Browser
(User’s computer)
Web server
stores HTML documents
Data Bases
and other files
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Perl Library –
Perl is a modularly extensible language, - many different modules ( reusable
pieces of software) have been written by Perl developers around the world.
Perl modules are defined in library files ending in .pm
Comprehensive Perl Archive Network (CPAN) ww.cpan.org is the distribution center for
Perl source code.
Users of ActivePerl and implementation of Perl for Windows created by ActiveState
Tool Corporation – can use Perl Package Manager (PPM) to find the install procedures.
Dynamic and static Web pages –
A static web page is an HTML document stored on the local machine or the server
A dynamic web page is an HTML document that can control the display of elements in a
Web page. Scripts (code) are included in the Web page and executed by the Web
browser.
Scripts can be written in various languages ( VB script, Java Script, AppleScript, Unix
shell scripts, Perl scripts …
CGI describes the set of protocols through which applications , i.e. CGI programs or CGI
scripts interact with Web servers and with clients ( Web browser).