Hit Counters

Up until now, every CGI we have used has required the user to hit a 'submit' button on an HTML page, at which point the entire window is replaced by a new page.  You could easily write a program using the skills you have already learned to open a count file, add 1, and replace.  It would look something like this:

#******** BEGIN BODY ********
open (GETCOUNT,"<count.log");            #open count log for input
$counter=<GETCOUNT>;                      #assign contents of file to $counter
close (GETCOUNT);                              #close access to file

$counter++;                                                 #increase $counter by 1.
print "$counter hits";                                #print number of hits to users screen

open (PUTCOUNT,">count.log");            #open count log for output
print PUTCOUNT ($counter);                #replace old counter value with new one
close PUTCOUNT;                                # close access to file

#******** END BODY *********

If we were to call such a program with a SUBMIT button, the current page would dissapear and be replaced by the output of this program.  In order to display the hits on our page, we need a way to execute a program when a page loads, and embed the results back in that same page.  This method is called a Server Side Include (SSI).

NOTE: Not all web servers support SSI.  Some only work if the pagename ends with  ".shtml" or ".html-ssi" and some have it completely disabled for security purposes.  If you have difficulty with this exercise, check with your system administrator.

Here's how it works:

• Insert the program above into a fresh copy of 'template.txt'.  Name the file count.cgi.
• Create a file containing only the starting number of hits.  Name this file count.log  .
• Open any HTML page, or create one from scratch.
• Insert this line somewhere in the HTML page.
  <!--#exec cgi="count.cgi"-->
  (If you use a cgi-bin, you should upload the cgi to that, and the command above should read
  <!--#exec cgi="/cgi-bin/count.cgi"-->       )
• Upload all 3 files to your server.
• Telnet to the perltour folder, and type   chmod a+rx count.cgi
• Browse to the html page, and reload it a few times.  You should see the number of hits increase.

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