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What is Perl? PERL--Practical Extraction and Report Language
Created as a way to process large text or files. Create a script that opens one or more files Processes the information Writes out results
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WWW functionality Communication with web servers through CGI
Perl takes input from a web form channels through the server and “does something with it.”
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What can it do? Perl can be used quite flexibly to “do something” with user input append to a flat file add it to a database insert it into an message add it to an existing webpage create a new webpage display it in the browser’s window
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Most impressive! A new webpage can be created “on the fly” in response to user input a thank you message a confirmation page a follow-up query information returned from a database query Web interactivity!
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Informations in Perl Online documentation on Perl Books on Perl
follow a tutorial hyperlink Books on Perl Learning Perl from O’Reilly & Associates Series on Perl from O’Reilly & Associates
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Perl Examples I Create a first Perl program, “first.pl”
#!/usr/local/bin/perl print “Hello, World\n”; chmod 755 first.pl ./first.pl
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Perl Example II Variables and Input Commands
#!/usr/local/bin/perl $name="HAL"; print "Hello there. What is your name?\n"; $you = <STDIN>; chop($you); print "Hello, $you. My name is $name. Welcome to the CGI Class.\n"; There is no type in $variable_name
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Perl Example III Perl CGI program has to handle HTML !!
#!/usr/local/bin/perl print "Content-type:text/html\n\n"; print "<html><head><title>Test Page</title></head>"; print "<body>"; print "<h2>Hello, world!</h2>"; print "</body></html>"; This handles HTML output only, how about input? --> needs HTML FORM
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Program vs. Script A program is a complex set of instructions, compiled in an efficient binary format for a given platform. A script is a set of instructions that is not compiled, but is left in plain text format. Needs an interpreter to execute.
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Alternatives C, Visual Basic ASP(Active Server Page) Java
JavaScript, VBScript Cold Fusion
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What You Need to Make It Work
A script Perl software A web form A web server
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Key Elements In the context of a web application, a script is just a series of instructions that tell the computer how to “do something with” the information a user provides. The “do something” is the “action.” Can be simple or elaborate
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Structure of Perl CGI Script
1. Setup 2. Parse 3. Process the Input 4. Show the results
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Simple, but Effective Perl is a relatively simple way to handle the output from HTML forms via CGI. Not the most efficient, but is the most commonly used for simple applications that do not get a high volume of user traffic and do not require sophisticated database processing and query.
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