CGIs

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CGIs

• Server-Side Programming

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What is a CGI?

• CGI -gt Common Gateway Interface - a way for web
  pages to access computer programs stored and
  running (key concept!!!) on a web server.
• PPBHS uses CGIs in Dashboard Page..
• CGI Programs mainly used for Form Validation,
  E-Commerce, Guest Books, etc...

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CGIs

• CGI programs can be written in any programming
  language most written with ASP (Active Server
  Pages - Server-Side JS - Dashboard page - ASP
  only works on MS Web Servers), C, or PERL
• Two Major Types of Web Servers UNIX (Apache)
  Servers and MS IIS (ASP).

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CGIs

• We will first learn PERL since we need for the
  commercial sites we are developing -- -gt onednr
  servers -- -gt OCPO, FVINCENT, LENNYSMARKET, and
  TRIC are hosted -gt UNIX Apache Servers.
• We need Guest Book CGI for FV Bulletin Board for
  OCPO, etc.

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PERL

• PERL - Practical Extraction and Report Language -
  high-level, interpreted lang. - not even designed
  for use with web (more info can be found at
  http//www.perl.com) created in 1986 to easily
  create reports
• PERL is easily ported from one OS to another
  (because it is interpreted)

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PERL

• Has a rep for being a cool lang
• and for being fun most of you guys know JS so it
  will be fairly easy for you guys to pick up..

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PERL

• How is PERL called out from a HTML
• Heres how you interface via a form
• ltFORM METHODpost ACTIONhttp//www.lennysmarket.
  com/cgi-bin/bulletin.cgigt
• Most CGI programs are stored in a directory
  called cgi-bin (perms need to be set for script).

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PERL Data

• 3 5 (result is 8)
• 3 cream (result is 3)
• ice cream (result 0)
• ice . cream (result icecream -gt
  concatenation)

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PERL Data

• print 3 Main Street (print is the Perl
  function to print back to web page 3 Main
  Street is a constant)
• variables
• address3 Main Street
• print address
• sum3 5

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Perl Data

• Print what is up\ndont know
• produces what is up
• dont know
• print you won prize

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Steps in Creating a PERL CGI Script

• Using NotePad/WordPad/Word - simple text editor..
• Code Perl Program
• Save as text-only file with extension cgi
• e.g., nick.cgi.
• Save in servers CGI-BIN Directory -gt in UNIX
  (Apache Servers run on- exec perm).

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Creating a PERL Script

• An Example simple web page with a form form
  asks you to enter your favorite animal and looks
  like this.. -gt web page with form prompting for
  favorite animal

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Creating a Perl Script

• The Perl script (CGI) is invoked from a real UNIX
  Apache Server via the Action parameter in the
  HTML Form tag ltform method"POST"
  action"http//www.ppea.info/cgi-bin/form.cgi"
  name"animal-form"gt Which Animal? ltinput
  typetext name"animal" size"20" gt

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Perl..

• Action statement in Form action"http//www.ppea.
  info/cgi-bin/form.cgi"
• Name in Form name"animal-form"
• Form Static Text and Variable where animal type
  goes Which Animal? ltinput typetext
  name"animal" size"20" gt

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Perl the script on the Server

• The Perl Program code for form.cgi
• The first line of the Perl script
  !/usr/bin/perl wT -gt indicates the path
  on the Server where the Perl interpreter resides
  remember Perl is interpreted and must be run by
  a Perl interpreter it is required..
  

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Perl the script on the Server

• The wT argument on the Perl Path line tells the
  Perl interpreter to warn you of any potential
  script problems (not required)
• The next line in the script use strict will
  required you to declare your variables (not
  required)

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Perl the script on the Server

• Next line use CGI standard tells Perl you
  are writing a CGI script and Perl should bring in
  its CGI Functions .. (this is required!!!)
• Now we can start writing our code!!!

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Perl the script on the Server

• my animal -gt we are defining a variable
  call animal right now theres nothing in it!!
• animal param(animal) -gt takes the data
  from the field labeled animal in your HTML Form
  which is calling this script..

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Perl the script on the Server

• print "Content-type text/html\n\n" -gt this
  line is required before you start sending
  information back to your web page via the Perl
  Print Function -- tells the web page that what
  is being returned is html text.

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Perl the script on the Server

• Last Line of Script simply prints/sends the
  animal entered in the web page back to the web
  page
  print "ltPgtShow me the animal..." -gt via the
  Perl print function we send back the information
  contained in the animal variable (a variable is
  a container) notice we have embedded HTML in
  the print string -gt ltPgt -gt everything within

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Now we need to use Perl to write a Bulletin Board
for OCPO