intermediate cgi & cgi.pm webmaster ii - fort collins, co copyright © xtr systems, llc cgi...

Intermediate CGI & CGI.pmWebmaster II - Fort Collins, CO

Copyright © XTR Systems, LLC

CGI Programming &

The CGI.pm Perl Module

Instructor: Joseph DiVerdi, Ph.D., MBA



CGI in a Nutshell

• CGI specifies how a Web Server software to communicates with other programs running on the server computer

• Why Bother?– Create Dynamic Web Pages

• "on-the-fly"

– Process user-supplied HTML form data



CGI In Brief



CGI & Perl

• CGI applications can be written in almost any language– But CGI & Perl have become virtually synonymous

• "Perl is the duct tape of the Internet"– Hassan Schroeder, Sun's First Webmaster

• Perl is by far the most widely used language– For creating CGI Programs



CGI & Perl

• Easy to Learn– Resembles Other Popular Languages– Forgiving With Detailed Error Messages

• Rapid Development Cycle– Interpreted Without a Separate Compile Phase

• Easily Portable– Available on Many Platforms

• Extremely Powerful String Manipulation– Powerful Built-In String Operators– Native Regular Expression Support



Setting Up For CGI Programs

• Create cgi Directory in html Directory– Case Is Very Important!

• Ensure cgi Directory Has 755 Permission– HTML-Kit Does This Automatically

• Programs Must Be Placed in This Directory– Server Is Configured Only to Execute From There– Programs Viewed From Other Directories

• Will Not Execute • Program Contents Will Be Rendered on the Browser



Short Examples

• Following Series of Code Snippets– Short Examples – Demonstrate Several Ways– Emit HTML From a Perl CGI Program

• "There's More Than One Way to Do It"– Programming Perl

• Worth Studying– You Can Develop Your Own Preferred Style– Some Methods Are Better in Some Situations– You Can Read Other Programmers' Code



Simple CGI Program in Perl

#!/usr/bin/perl

print "Content-type: text/html\n\n";

print "<HTML>\n";

print "<HEAD>\n";

print "<TITLE>\nHello world!\n</TITLE>\n";

print "</HEAD>\n";

print "<BODY>\n";

print "Hello world!\n";

print "</BODY>\n";

print "</HTML>\n";

exit;

• Create a File Named "simple.pl"



Simple CGI Program in Perl

#!/usr/bin/perl


print "<HTML>\n";

print "<HEAD>\n";

print "<TITLE>\nHello world!\n</TITLE>\n";

print "</HEAD>\n";

print "<BODY>\n";

print scalar(localtime(time())), "\n";

print "</BODY>\n";

print "</HTML>\n";

exit;

• Create a File Named "time.pl"



Escaping Quotes

#!/usr/bin/perl


print "<HTML>";

print "<HEAD>";

print "<TITLE>Hello world!</TITLE>";

print "</HEAD>";

print "<BODY BGCOLOR=\"#66FFFF\">";


print "</BODY>";

print "</HTML>";

exit;

• Modify time.pl• Escaping Will Get Old Fast



Pick Your Own Quotes

#!/usr/bin/perl

print qq(Content-type: text/html\n\n);

print qq(<HTML>\n);

print qq(<HEAD>\n);

print qq(<TITLE>\nHello world!\n</TITLE>\n);

print qq(</HEAD>\n);

print qq(<BODY BGCOLOR="#66FFFF">\n);


qq(Hello world!\n);

print qq(</BODY>\n);

print qq(</HTML>\n);

exit;

• Called "Double Quote" Operator



"Here" Documents

#!/usr/bin/perl

print <<__END_OF_HTML__;

Content-type: text/html

<HTML>

<HEAD>

<TITLE>hello world!</TITLE>

</HEAD>

<BODY>Hello world!</BODY>

</HTML>

__END_OF_HTML__

exit;

• Be Careful of Ending Delimiter



Multiple Delimiters

#!/usr/bin/perl

print <<__HTML_1__;

Content-type: text/html

<HTML><HEAD><TITLE>hello world!</TITLE></HEAD>

<BODY>

__HTML_1__


print <<__HTML_2__;

</BODY></HTML>

__HTML_2__

exit;



Perl Modules

• There's Got to Be a Better Way...• Modular System of Reusable Code

– Created by Many Different Authors– Archived in Massive CPAN System– Easily Imported Into Your Programs– Provides Functionality at Many Levels



CGI.pm Module

• Become the Standard Tool in Perl– For Creating CGI Scripts

• Provides Clean & Simple Interface– For Emitting HTML Code From Scripts– For Most Common CGI Tasks

• Generates HTML Output• Accepts FORM Input

– Can Parse FORM Input Parameters

• Provides Error Handling



Handling Input

• Environment Information– Methods to Access %ENV Information

• FORM Input– Automatically Parses FORM Data– Provides Simple Methods for Access

• File Upload– Permits CGI Script to Handle HTTP File Uploads

• Easily, Safely, & Transparently



Generating Output

• Generating Headers– Methods to Emit HTTP Headers

• Various Content & Server Redirection

• Generate HTML– Method to Generate Full HTML Documents

• HTML Generation Alternatives– Quoted HTML & Here Documents



Error Handling

• Trapping Die– die Does Not Work Well With CGI

• "Internal Server Error" Report

• CGI::Carp– Provides Methods for Trapping Die & Other Errors

• Custom Solutions– Provides More Control When Displaying Errors

• Create a Custom Subroutine or Module



CGI.pm Documentation Page

• Always the Latest At:

http://stein.cshl.org/WWW/CGI/



Simple CGI.pm Program

#! /usr/bin/perl

use warnings;

use strict;

use CGI qw(-no_xhtml);

my $q = CGI->new;

print $q->header(-type => 'text/html');

print $q->start_html(-title => 'Hello world!');

print $q->p('Hello world!');

print $q->end_html;

exit;



Adding CSS Control

#! /usr/bin/perl

use warnings;

use strict;


my $q = CGI->new;


print $q->start_html(-title => 'Hello world!',

-style => { -src => '/~diverdi/style/main.css' });


print $q->end_html;

exit;



Adding JavaScript Support

#! /usr/bin/perl

use warnings;

use strict;


my $q = CGI->new;


print $q->start_html(-title => 'Hello world!',

-style => { -src => '/~diverdi/style/main.css' },

-script => { -type => 'text/javascript',

-src=>'javascript/verify });


print $q->end_html;

exit;



Random Image Display

• Program Delivers Image to Browser– Chosen From Designated Directory– Chosen At Random

• See Web Site For Code



Image Selector

• Program Delivers Image to Browser– Chosen From Designated Directory– Chosen By Viewer's Selection– Not The Same As HTML Page

• List Of Links Varies According To Files In Directory




Survey System

• Program Maintains & Displays Survey Data– Accepts Viewer Data Submitted Through FORM– Maintains Data In Disk File On Server– Displays Results in General-Purpose Format– Displays Results in Form-Specific Format– Consists of Several, Separate Programs

• Programmer's Task Is to Synchronize Them




Survey System

• System Programs– Submit Survey– Create Simple Report– Create Fancy Report

• Each Program Is Installed in CGI Directory• Programs Are Accessed Through HTML

– Developer's Choice on Specifics

intermediate cgi & cgi.pm webmaster ii - fort collins, co copyright © xtr systems, llc cgi...

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