Tutorial 6: Working With Forms II
(The CGI)

The following tutorial presupposes that you have some familiarity with HTML authoring.
It does not teach you how to write a CGI script.
This is the script that handles the form in: template5.html.
Go to Tutorial5 to learn how to create the corresponding HTML document that contains the form.
Go to template6.pl to see this script.

This tutorial further assumes that you have the permission to install CGI scripts on your web server, and that this server runs the UNIX operating system and makes the Perl programming language available to you. Your system administrator or webmaster should be able to help you with specific questions.

The example script has been tested and is known to work on the following system:

FreeBSD v2.2
Apache v1.2
Perl v5.003

Note:

• The programming language used in this tutorial is Perl. You can use any other programming language available on your web server (C/C++, bash, REXX, etc.).
• The script is separated into lines, each of which ends with a semicolon (;)
• Variables are denoted by the $ sign in front of their names.
• User input from the HTML form is accessed as $FORM{'FieldName'}, where FieldName is the name of the HTML form element (checkbox, radio button, etc.).
• All lines that begin with # are called comments and are ignored by the script. We include them to make the script more readable and easier to understand. The script is visually separated into blocks by blank lines, which are also ignored. Blocks that begin with the line:

  # ********** #

  are the lines that we will have to modify to suit our specific system and exercise.
  
  

Changes you need to make to the example CGI script:

1. The very first line of the script specifies the path of the Perl programming language interpreter on the specific web server system we are using. In our case it reads:

   #!/usr/bin/perl

   An easy way to find out what should go into this line is to type

   which perl

   in your UNIX system's shell. The output of this commant should follow the # ! characters on the first line of the script. Also, your system administrator or webmaster should be able to tell you what goes in there.
   
   

2. A similar procedure as the one in the previous part can be used to find where the program sendmail is located. The variable $mailprog should contain this information. In our case, we use a line that says:

   $mailprog = '/usr/sbin/sendmail';

3. In the next block, we will specify the instructor's complete e-mail address. In our case, the address is jarana@leia.ursinus.edu, and the line reads:

   $teacher = ('jarana@leia.ursinus.edu');

4. Next, we make sure that the user filled all the required blanks. We do that with a block of lines, each of which looks like this:

   blank_&response unless $FORM{'FieldName'};

   where FieldName are the names of all required fields in the HTML form. Each form element (pull-down menu, check box, etc.) that you want to be required needs to appear in one of these lines.
   
   

5. Next, the most important part, we will generate the e-mail message that is sent to the instructor. We will have to modify all lines in this section starting with the Subject: line. You determine the content and the format of the message.
   
   
   • Each line should have the format:

     print MAIL "text";

     where text is the the text that you will get in the e-mail message.
     
     

   • To generate a line break (as if you hit the [Enter] key in a word processor), include the characters \n.
     
     
   • User input from the HTML form is accessed as $FORM{'FieldName'}, where FieldName is the name of the HTML form element (checkbox, radio button, etc.).
     

   
   

6. Lastly, in the next block, we provide a feedback web page for the user. This is an HTML page generated by the script using the print statement (without the word MAIL), and may include the input submitted by the user in the same format as in the e-mail.
   To avoid any problems with quotes ( " ), precede them with a backslash ( \ ).
   
   

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