How CGI Programs Work

Most CGI programs include the following three stages:

vParsing CGI programs

vData manipulation within a CGI program

vResponse generation by a CGI program

Parsing

Parsing is the first stage of a CGI program. In this stage, the program takes the data from QUERY_STRING environment variable, command line arguments using argv() or standard input. When the method is GET, the system reads the data from the QUERY_STRING environment variable or command line arguments by using argv(). There is no way to determine the length of data in QUERY_STRING. The system encodes the QUERY_STRING data in the request header.

An example of data read in the QUERY_STRING variable (%%MIXED%% mode):

NAME=Eugene+T%2E+Fox&ADDR=etfox%40ibm.net&INTEREST=RCO

Parsing breaks the fields at the ampersands and decodes the ASCII hexadecimal characters. The results look like this:

NAME=Eugene T. Fox

ADDR=etfox@ibm.net

INTEREST=RCO

You can use the QtmhCvtDb API to parse the information into a structure. The CGI program can refer to the structure fields. If using %%MIXED%% input mode, the “%xx” encoding values are in ASCII and must be converted into the “%xx” EBCDIC encoding values before calling QtmhCvtDb. If using %%EBCDIC%% mode, the server will do this conversion for you. The system converts ASCII “%xx” first to the ASCII character and then to the EBCDIC character. Ultimately, the system sets the EBCDIC character to the “%xx” in the EBCDIC CCSID. For code samples, use the following URL to the AS/400 web site:

http://www.as400.ibm.com/tstudio/index.htm.

When the method is post, the system reads the data from standard input. Before the CGI attempts to read standard input, it must check environment variables REQUEST_METHOD and CONTENT_LENGTH. Read standard input only when the REQUEST_METHOD is POST. The read must specify no more than CONTENT_LENGTH bytes. Attempts to specify more than CONTENT_LENGTH bytes on reading standard input are not defined.

Data manipulation

Data manipulation is the second stage of a CGI program. In this stage, the program takes the parsed data and performs the appropriate action. For example, a CGI program designed to process an application form might perform one of the following functions:

1.Take the input from the parsing stage

2.Convert abbreviations into more meaningful information

3.Plug the information into an e-mail template

4.Use SNDDST to send the e-mail.

Response generation

Response generation is the final stage of a CGI program. In this stage, the program formulates its response to the web server, which forwards it to the browser. The response contains MIME headers that vary depending on the type of response.

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IBM AS/400E manual How CGI Programs Work, Parsing
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AS/400E specifications

The IBM AS/400E, now more commonly known as IBM i, is a robust and versatile midrange server that has been designed to provide a comprehensive computing solution for businesses of all sizes. First introduced in the late 1980s, the AS/400 series has undergone multiple enhancements and rebranding, with the AS/400E being one of the notable iterations. This powerful platform is closely associated with IBM's commitment to reliability, scalability, and integrated business solutions.

One of the main features of the AS/400E is its highly integrated architecture that combines hardware and software into a cohesive system. This integration allows for seamless operations, reducing the complexity typically associated with managing disparate systems. The system is powered by IBM's proprietary OS/400 operating system, which has evolved into IBM i, featuring advanced capabilities like object-oriented programming, integrated database management, and security features that are essential for enterprise environments.

A key characteristic of the AS/400E is its robust database support, primarily through the use of DB2 for i. This integrated database management system enables efficient data handling and retrieval, facilitating real-time business analytics and reporting. Furthermore, the platform supports a variety of programming languages, including RPG, COBOL, and Java, making it flexible for developers who require diverse tools for application development.

The AS/400E is also known for its exceptional reliability and uptime, making it a preferred choice for critical business applications in industries such as finance, healthcare, and manufacturing. This reliability is backed by advanced error detection and correction mechanisms, as well as redundancy features that help prevent data loss and minimize downtime.

In terms of scalability, the AS/400E can effortlessly expand to accommodate growing business demands. Organizations can increase processing power by adding more resources without significant disruption. This scalability, combined with the system’s built-in virtualization capabilities, allows businesses to optimize resource usage and streamline operations.

Security is another defining feature of the AS/400E. The platform incorporates various layers of security measures, including user authentication, encryption, and comprehensive auditing capabilities, ensuring that sensitive business data is protected against unauthorized access.

Overall, the IBM AS/400E remains a powerful tool in the enterprise computing landscape, providing businesses with an integrated, reliable, and secure solution for their technological needs. Its enduring popularity is a testament to its capability to evolve with changing business requirements while maintaining its core attributes of high performance and stability.
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