Transcript ch_09
Chapter Nine
Perl and CGI Programming
Objectives
Basic features of Perl language
Set up an HTML Web page
Use Perl and CGI scripts to make your
web pages interactive
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Introduction to Perl
Perl is a script language
– Elements of csh, sh, awk
Example:
#! /usr/bin/perl
# example of perl script
print(“hello world\n”);
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Variables
Scalar
$word = “test”
print(“here it is: $word \n”);
Array
@list = ("one", "two", "three");
print("here it is: $list[0]\n");
print("here it is: $list[1]\n");
print("here it is: $list[2]\n");
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Variables
Hash
%animals =
("cat",10,"dog",12,"fish",23);
print("1: $animals{'cat'}\n");
print("2: $animals{'dog'}\n");
print("3: $animals{'fish'}\n");
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Command line arguments
$ARGV[0], $ARGV[1], …
print("$ARGV[0], $ARGV[1]\n");
With a loop:
$size = @ARGV;
for ($i = 0; $i < $size; $i++)
{
print("$ARGV[$i]\n");
}
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Reading Input
Standard input
print("enter a number: ");
$number = <STDIN>;
print("here it is: $number");
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Reading from a File
if (!open(FILE, "$ARGV[0]"))
{
print("cannot open:
$ARGV[0]\n");
}
while ($line = <FILE>)
{
print("$line");
}
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Setting Up a Web Page
Web pages can be created using HTML
(Hypertext markup Language)
HTML is a format for creating documents with
embedded codes known as tags and when the
document is viewed in a Web browser, the tags
give the document special properties
After using HTML to create a Web page, the
page is published on a Web server, this allows
others to access the document via the Internet
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Creating a Web Page
HTML documents are created by typing its
text and the desired embedded tags
There are two parts to the HTML code
– The head contains the title, which appears on
the top bar of the browser window
– The body defines what appears within the
browser window
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CGI Overview
CGI (Common Gateway Interface) is a protocol,
or set of rules, governing how browsers and
servers communicate
Scripts that send or receive information from a
server need to follow the CGI protocol
Perl is the most commonly used language for
CGI programming
Perl scripts are written to get, process, and
return information through Web pages
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Perl Libraries
Libraries of functions:
use CGI qw(:standard);
print(header);
print(start_html("Hello World"));
print h2("Test Website");
print(end_html);
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Setting up a Web Page
Create subdirctory
public_html
add files:
index.html
ten.cgi
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Interactive Web Page
<html><head>
<title>COP 3344</title></head>
<body>
<h1>User Inquiry</h1>
<form method=get action=eleven.cgi>
Enter your name:
<input type="text" size=20
name="userid"><br>
<input type="submit" value="Submit">
</form>
</body></html>
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Interactive Web Page
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Interactive Web Page
#! /usr/bin/perl
# example perl script
use CGI qw(:standard);
print(header);
print(start_html("Anser Page"));
print h2("Answer Page");
print("Welcome: ", param('userid'));
print(end_html);
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Interactive Web Page
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Chapter Summary
Perl is a powerful scripting language
Perl scripts are used to create web pages
An HTML document contains two parts: a
head and a body
CGI is a protocol or set of rules
governing how browsers and servers
communicate
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