The functions and tasks that CGI programs can perform range from the simple to
the very advanced. In general, we call those that perform the simple tasks CGI
scripts because you do not compile them. We often call those that perform
complex tasks gateway programs. In this manual, we refer to both types as CGI
programs.
Given the wide choice of languages and the variety of functions, the possible uses
for CGI programs seem almost endless. How you use them is up to you. Once you
understand the CGI specification, you will know how servers pass input to CGI
programs and how servers expect output.
There are many uses for CGI programs. Basically,you should design them to
handle dynamic information. Dynamic in this context refers to temporary
information that is created for a one-time use and not stored anywhere on the web.
This information may be a document, an e-mail message, or the results of a
conversion program.
For detailed information about AS/400 CGI APIs, see “Chapter2. Application
Programming Interfaces”on page 23.
CGI and Dynamic Documents
There are many types of files that exist on the web. Primarily they fall into one of
the following categories:
vImages
vMultimedia
vPrograms
vHTML documents
Servers break HTML documents into two distinct types:
vStatic
vDynamic
Static documents exist in non-changing source form on the web server. You should
create Dynamic documents as temporary documents to satisfy a specific, individual
request.
Consider the process of ″serving″, these two types of documents. Responding to
requests for static documents is fairly simple. For example, Jill User accesses the
Acme web server to get information on the Pro-Expert gas grill. She clicks on
Products, then on Grills, and finally on Pro-Expert. Each time Jill clicks on a link,
the web browser uses the URL that is attached to the link to request a specific
document from the web server. The server responds by sending a copy of the
document to Jill’s browser.
What if Jill decides that, she wants to search through the information on the Acme
web server for all documents that contain information on Acme grills? Such
information could consist of news articles, press releases, price listings, and service
agreements. This is a more difficult request to process. This is not a request for an
existing document. Instead, it is a request for a dynamically generated list of
documents that meet certain criteria. This is where CGI comes in.
You can use a CGI program to parse the request and searchthrough the
documents on your web server. Youcan also use it to create a list with hypertext
links to each of the documents that contain the specified word or string.
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