CGI Web Programming
This is the start of a tutorial about cgi web programming. Everyone is invited to contribute.
A very basic example
Here is an example of a minimal CGI program to demonstrate...
- Setting a cookie
- Outputting the content-type (ie make it put out legal text for HTTP)
- Reading Cookies
- Reading form data via GET
- Reading form data via POST
program mini; uses dos; var a:string; c:char; begin //set a cookie (must come before content-type line below) //don't forget to change the expires date writeln('Set-cookie:widget=value; path=/; expires= Mon, 21-Mar-2005 18:37:00 GMT'); //output legal http page writeln('Content-Type:text/html',#10#13); //demonstrate get cookies a:= GetEnv('HTTP_COOKIE'); writeln('cookies:',a); //demonstrate GET result a:=''; a:= GetEnv('QUERY_STRING'); writeln('GET: ',a); //demonstrate POST result a:=''; while not eof(input) do begin read(c); a:= a+c; end; writeln('POST: ',a); end.
A simple hitcounter
The application hitcounter presents a simple hitcounter for your website. It is possible to enter blocklists in a configfile so robots and perhaps your own computer are excluded from the statistics. There are still a lot of improvements possible ofcourse like setting a cookie so you get only one hit per session, but it gives a good introduction into CGI programming. If you use the code and modify it, please send me a patch so I can update it.
You can find the code here: [1]
Existing CGI Frameworks
There are existing CGI units and frameworks that make working with CGI trivial (and allow one to set cookies, sessions, retrieve POST and GET). See Powtils
There is also a CGIModule for lazarus, and a few CGI and HTML units in the freepascal FCL.