CSU - DCE Advanced Perl CGI 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 Advanced Perl CGI 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 Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC CGI In Brief

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Uses of CGI Web Clock Changes from one viewing to another

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Uses of CGI Simple Survey

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Uses of CGI Simple Game

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Uses of CGI Quiz

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Uses of CGI Search Engine

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Uses of CGI Database access

CSU - DCE Advanced Perl CGI 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 Advanced Perl CGI 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 Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Dynamically Created Image Web Clock

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC Dynamic Image Inclusion Digital Clock Demo

CSU - DCE Advanced Perl CGI 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 Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC CGI Interaction

CSU - DCE Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC CGI and Form Processing

CSU - DCE Advanced Perl CGI 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 Advanced Perl CGI Operation - Fort Collins, CO Copyright © XTR Systems, LLC CGI Gateway to a Database

CSU - DCE Advanced Perl CGI 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 Advanced Perl CGI 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! \n"; exit; Save file in "cgi" Ensure program has "rwxr-xr-x" access Test using telnet client Test using browser

CSU - DCE Advanced Perl CGI 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! \n"; print "The current time is ", scalar localtime, " \n"; print "You are using the computer named: ", $ENV{'REMOTE_HOST'}, " \n"; exit;

CSU - DCE Advanced Perl CGI 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 Advanced Perl CGI 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= "

CSU - DCE Advanced Perl CGI 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