A Web-Based Lunch Ordering System

I then placed the lunch.html file in the directory /home/httpd/html:

$ cp lunch.html /home/httpd/html

(This is the default location Apache looks for html files. It can be configured to look elsewhere.) Once you have done this, you can see what lunch.html looks like by browsing http://localhost/lunch.html using Netscape (or any browser).

Write the CGI script with Python, which is distributed with the Red Hat Linux distribution (see http://www.python.org/). After consulting the Python documentation, which also came with the system, my first script looked like the one shown in Listing 3. It is essentially a cannibalised version of an example found in the Python documentation. To make use of this script, you'll need to point the CGI script specified in the ACTION statement in the HTML file to this script instead. That is, change the cgi script specified in the ACTION statement from lunch.cgi to first.cgi.

I then copied first.cgi to the directory /home/httpd/cgi-bin:

$ cp first.cgi /home/httpd/cgi-bin

Essentially, I interrogated all the variables sent to the script by the form and printed it back out. All output printed will be displayed by the browser.

#-----------------
 1 #!/usr/bin/env python
 2 # first.cgi
 3 import cgi                                   # import the cgi module
 4
 5 print "Content-Type: text/plain\n\n"       # necessary for the
browser
 6
 7 lunchForm = cgi.FieldStorage()               # retrieve the values
 8
 9 for name in lunchForm.keys():
10     print "Key= " + name + " Value= " +
lunchForm[name].value + " "
11
12 print "bye."
#-------------

Figure 2. Output of Script first.cgi

You will notice that the keys found in the CGI script correspond to the variables I used in lunch.html.

Once I got this simple script working, I then expanded it to do what I wanted (see Listing 3). The Python code is quite straightforward and self-explanatory. It imports the CGI module, then calls the member function FieldStorage() of CGI. Whether the information is sent using the GET or POST method is hidden from you. That's how all the information sent by the web page is retrieved. The information can then be extracted by accessing lunchForm.

Listing 2

The body of the mail sent is then constructed via a series of writes to sendmail, a UNIX sendmail mail transfer agent. I decided to mail the lunch order to user lunch@localhost. An alias can be inserted in file /etc/aliases:

lunch:          chai@localhost

where user chai@localhost is organising the orders. This way, if the lunch organiser gets changed, the file /etc/aliases needs to be changed and not the CGI script. (newaliases needs to be run for changes to /etc/aliases to take effect).

Easy, eh? Well, it could be much worse.

I then copied lunch.cgi to the directory /home/httpd/cgi-bin:

$ cp lunch.cgi /home/httpd/cgi-bin

I opened Netscape, typed in http://localhost/lunch.html as the URL, filled in the form, selected my order and clicked on “Go”.

Sometime later, an e-mail arrived outlining the order.

Here is what the received e-mail of the lunch order, sent by the CGI script, looks like:

>From nobody@localhost  Wed Apr 26 11:01:50 2000<\n>
Delivered-To: ccang@localhost
Date: Wed, 26 Apr 2000 11:01:48 +1000
To: lunch@localhost
From: chai <calcium@altavista.net>
Subject: loi loi
Sender: nobody@localhost
SourceIP 194.118.1.1
calcium@altavista.net
Wed Apr 26 11:01:01 GMT+1000 (EST) 2000
chai wants
1. L39 with Steamed rice.
2. NONE with NA rice.
3. NONE with NA rice.
4. NONE with NA rice.

Figure 3 shows what the web page looks like after the request has been sent.

Figure 3. Snapshot of Resulting Web Page After Lunch Order Made