Turbo Pascal CGI for a Windows WHTTPD Server

1. The user fills in HTML form & presses the submit button
2. The browser sends the information filled into the form and the form parameters (including the CGI application to be launched) to the server.
3. The server takes the form information and
   
   1. writes it to a local file
   2. sets an environment variable to the name of that file
   3. sets another environment variable to the name of the output file
   4. launches the CGI application
4. When the CGI application runs it:
   
   1. reads the names of the user input & output files from the environment variables
   2. generates the output based on the input
   3. writes the output to the output file
   4. terminates
5. The server returns the contents of the output file to the browser for the user to read

1. Read the input data file name from an environment variable. The environment variable concerned is CONTENT_FILE. The GetEnv function can be used for this purpose.
2. Read the output file name from an environment variable. OUTPUT_FILE in this case. Again, GetEnv can be used.
3. read the input data from the file specified by CONTENT_FILE. This is in the form
   field1=field1data&field2=field2data&field3=field3data. . . etc
   Any spaces entered by the user will be replaced by + signs. IE My Name becomes My+Name.
4. process the data
5. write the output to the output file as HTML code. The first line of the file must contain a content type specification in the form:
   Content-Type: text/html
   followed by a blank line
6. terminate

First the application (HELLO.PAS):

program hello;

uses dos;

var
   infile,outfile:text;
   name,inputline:string[80];
   equals,character:integer;

begin
     assign (infile,getenv('CONTENT_FILE'));
     assign (outfile,getenv('OUTPUT_FILE'));

     {Open the content file, read the user's input & close the file}
     reset(infile);
     readln(infile,inputline);
     close(infile);

     {Extract the users name from the input line}
     equals:=pos('=',inputline); {Find the position of the first = sign}
     name:=copy(inputline,equals+1,length(inputline)-equals);

     {Change + signs in name to spaces}
     for character:=1 to length(name) do
         if name[character]='+'
            then name[character]:=' ';
   
     {Open the output file, write the content type, write the 
     output & close the file}
     rewrite(outfile);
     writeln(outfile,'Content-Type: text/html');
     writeln(outfile);
     writeln(outfile,'<H1>Hello ',name,'</H1>');
     writeln(outfile,'<A HREF="/hello.htm">Back</A><P>');
     close(outfile);
end.

Then the form (HELLO.HTM):

<FORM METHOD="POST" ACTION="/cgi-bin/hello.exe">
Enter Your Name: <input name="name"  size=20><P>
<input type=submit><P>
</FORM>

These two files are in the directory C:\TPCGI

<A HREF="\cgi-bin\details.exe?jsmith">John Smith</A>

This link would launch the CGI application DETAILS.EXE, but instead of the parameter jsmith being passed via the file pointed to by CONTENT_FILE, jsmith is stored directly in the environment variable QUERY_STRING. To retrieve this parameter from within DETAIL.EXE we would use a pascal statement like this:

name:=getenv('QUERY_STRING');

An application that comes quickly to mind is conducting surveys. You could set up a form with fields for Age, Sex, and Favorite Food, or perhaps Date, Temperature and Rainfall. When the user submits the form, the CGI application could write the three fields to a data file, with commas between each field, and send a page back to the user thanking them for participating in the survey. When the survey period finishes, the data file can be read into a spreadsheet or database for analysis.

A system like this could be used on an Intranet server to collect data from multiple students, over a period, into a single database.

A more sophisticated version for older students could ask the person filling the form to enter an email address if they would like to get a copy of the survey results emailed to them.