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Chapter 1 Introduction to Perl and CGI

Learn about the World Wide Web, web browsers, HTML files, and common gateway interface (CGI) in this introduction to Perl programming for web applications.

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Chapter 1 Introduction to Perl and CGI

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  1. Chapter 1 Introduction to Perl and CGI

  2. World Wide Web Background • The World Wide Web (WWW) is a collection of millions of documents and files that are accessible via the Internet • Web browsersare special computer programs that know how to retrieve and display files from the World Wide Web. Can work with • Play a file in the wav format (a sound file) • Interpret and then display a file in a gif format ( a digital picture file) • Interpret and then display a file in the HTML format (a text-based Web page)

  3. Accessing HTML Files Over the Internet

  4. HTML? • The Hypertext Markup Language(HTML) uses coded commands called HTML tagsthat provide instructions to Web browsers indicating how to display each page

  5. Displaying HTML

  6. Web Application Program • Carriesout many dynamic tasks, such as the following: • Input a search term, search the WWW, and return the results • Calculate and display the number of times that a page has been viewed • Verify the input fields on a Web form • Save a Web form into a database • Display a special graph, or return the results of a calculation based on data input from a form

  7. The Common Gateway Interface • a standard that enables Web browsers to exchange data with computer programs located on a Web server • first appeared in the NCSA HTTPD Web server software built by the National Center for Super-computing Applications (NCSA). • one of the first widely used Web servers • was simple and the program source code was made available for free • It is simple to use and available on a variety of Web servers.

  8. How Browsers and Web Applications Work with CGI

  9. An Interface with Different Programming Languages • Web application programs that are developed specifically to work with the CGI standard are known as CGI programs. • Lots of different programming languages can be used. For example, • Perl, • Visual Basic, • Java, • C, • C++, • and UNIX shell scripts.

  10. The Perl Programming Language • Practical Extension and Reporting Language • invented in 1987 by Larry Wall at NASA’s Jet Propulsion Laboratory • developed as a utility programming language for the UNIX operating system • gained popularity because of its ease of use, free availability via the Internet, and its powerful combination of

  11. Why Perl is Popular • Perl is a free language with lots of free applications • Perl is easier to work with than many other languages • Perl provides a CGI interface module • Perl applications are portable.

  12. Why Perl is Popular • Perl is a free language with lots of free applications • Perl is easier to work with than many other languages • Perl provides a CGI interface module • Perl applications are portable.

  13. Internet Service Provider Issues • Some things to determine with your ISP • Allow CGI programs to execute on its Web-server? Does it have Perl? What Version? • Login and initial password on the Web server? • Where do you put your Perl programs on the Web server and what permission settings? • How much disk space for publishing? • Support FTP and/or Telnet access?

  14. FTP Vs Telnet Access

  15. Summary • Web pages written in HTML are static and cannot interact with users. • CGI is an interface standard that allows computer programs to communicate with Web servers.Several programming languages can be used with CGI.

  16. Summary - II • Perl is a popular computer language that can be used for developing CGI programs. • You can install Perl and your own Web server software on your PC or workstation. • If you use an ISP’s Web server, find out several things about its services.

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