CGI - General Presentation

1. CGI Sopan Shewale , sopan.shewale@gmail.com

7. How a CGI Applications Work? CGI Application User Web Browser 1 2 3 4 HTTP Request HTTP Response CGI Program’s Response Call CGI Server Application (on Server)

22. Example: Count Click Script #!/usr/bin/perl # ######################### ## Author: Sopan Shewale ### This script is created for giving demo on click count. ## The Script is support to display increse/decrease click's, handles back button of browser, does not handle reload stuff. ## also it's based on sessions. ######################## use strict; use warnings; use CGI; use CGI::Session; use CGI::Cookie; my $q = new CGI(); my $sessionid = $q->cookie(&quot;CGISESSID&quot;) || undef; my $session = new CGI::Session(undef, $sessionid, {Directory=>'/tmp'}); $sessionid = $session->id(); my $cookie = new CGI::Cookie(-name=>'CGISESSID', -value=>$sessionid, -path=>&quot;/&quot;); print $q->header('text/html', -cookie=>$cookie); print $q->start_html(&quot;Welcome to Click Count Demo&quot;); print &quot;<h1>Welcome to Click Count Demo</h1>&quot;; my $count = $session->param('count'); ## count-is click count variable if(!defined($count)) { $session->param('count', 0); $count=0;} ### if session is first time created, set count=0 $session->param('count', $count); $count = $session->param('count'); #print &quot;<h1>The Click Count is: $count &quot;; ## Form stuff print $q->startform(-method=>'POST'); print $q->submit( -name=>&quot;Increase&quot;, -value=>'Increase1'); print $q->submit( -name=>&quot;Decrease&quot;, -value=>'Decrease1'); print $q->endform();

23. Example: Count Click Script (Cont…) ## Which button is being pressed my $which_button = $q->param('Increase'); if(defined ($which_button)) { print &quot;Increase pressed&quot;; $count = increase_count($count); ## Increase the count since increase button is clicked $session->param('count', $count); }else { $which_button=$q->param('Decrease'); if(defined($which_button)){ print &quot;Decrease pressed&quot;; $count = decrease_count($count); ## Decrease the count since decrease button is clicked $session->param('count', $count); } else {print &quot;You have not pressed any button, seems you are typing/re-typing the same URL&quot;; } } $count = $session->param('count'); print &quot;<h1>The Click Count is: $count &quot;; print $q->end_html(); ## increases the count by 1 sub increase_count { my $number = shift; $number = $number +1; return $number; } ## decreases the count by 1 sub decrease_count { my $number = shift; $number = $number -1; return $number; }

24. Example of Back- button Issue

27. Thank you For any queries write to Email: sopan.shewale@gmail.com