csu - dce 0723 - advanced perl cgi operation - fort collins, co copyright © xtr systems, llc...
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CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Introduction to the Common Gateway
Interface(CGI) on the Web
Instructor: Joseph DiVerdi, Ph.D.
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI In Brief
• CGI stands for Common Gateway Interface– It allows the web server to communicate with other
programs that are running on the server. For example:
– With CGI, the server causes an external program to execute while passing user-specific data to that program.
– That program processes that data, sends a response back to the server which passes the response back to the browser.
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI In Brief
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Web Clock
Changes from one viewing to another
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Simple Survey
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Simple Game
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Quiz
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Search Engine
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Database access
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Uses of CGI
• Not limited to previously written documents • Enables web pages to be created on-the-fly
– Based on the Users’ input
• Provide users with information, collect their comments, and respond
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Dynamic Page Content
• Page created dynamically via (Perl) script or• Page with Server Side Includes (SSI) or• Page with embedded call to (Perl) script• The result is still an HTML page
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Dynamically Created Image
• Web Clock
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Dynamic Image Inclusion
<HTML>
<HEAD>
<TITLE>Digital Clock Demo</TITLE>
</HEAD>
<BODY>
<IMG SRC="/cgi/digital_clock.pl">
</BODY>
</HTML>
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI Interaction
• Operation is as follows:– Client requests a document which actually is a
CGI program perhaps including some user-specific data
– Server executes requested program passing data received from browser request
– Program completes execution and generates a response
– Server returns response to browser
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI Interaction
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI and Form Processing
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI Database Interaction
• Combing the power of relational database management systems (RDBMS) with Web is very powerful.
• CGI program is required to decode input, assemble query, send to database, process return data from database, and create return document.
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
CGI Gateway to a Database
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Preparing to Use CGI
• Create directory "cgi" in "html" directory• CaSe iS vErY iMpOrTaNt!• Ensure cgi directory has "rwxr-xr-x" access• CGI programs must be located here• Ensure programs have "rwxr-xr-x" access• Always test program with telnet client FIRST!• Test using Browser and sample HTML page
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Simple But Useful Program
• Create a file "useful.pl"#! /usr/bin/perl -w
print "Content-type: text/html\n\n";
print "Hello, CGI Programmer!<BR>\n";
exit;
• Save file in "cgi"• Ensure program has "rwxr-xr-x" access• Test using telnet client• Test using browser
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
More Useful Program
• Modify the file "useful.pl"#! /usr/bin/perl -w
print "Content-type: text/html\n\n";
print "Hello, CGI Programmer!<BR>\n";
print "The current time is ", scalar localtime, "<BR>\n";
print "You are using the computer named: ", $ENV{'REMOTE_HOST'}, "<BR>\n";
exit;
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Simple Shell Program
• Create a file "env.cgi"#! /bin/sh
echo "Content-type: text/html"
echo
env
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Using Others' Programs
• Create a form page, e.g., Ice Cream Survey• Include the following HTML
<FORM METHOD=POST ACTION="http://www.xtrsystems.com/cgi/formmail.pl"
<INPUT TYPE=HIDDEN NAME="send_feedback_to" VALUE="your_email_address">
<INPUT TYPE=HIDDEN NAME="subject" VALUE="your_email_subject">
CSU - DCE 0723 - Advanced PerlCGI Operation - Fort Collins, CO
Copyright © XTR Systems, LLC
Using Programs
• Install formmail.pl in your account on linus• Download from class Materials Page• Upload to "cgi" directory• Check program access• Modify form HTML• Test with browser• Modify program (very carefully!!)• Have fun
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