Chapter 27 – CGI
(Common Gateway Interface) and Perl 5
Outline
27.1
Common Gateway Interface (CGI)
27.2
Introduction to Perl
27.3
Configuring Personal Web Server (PWS) for Perl/CGI
27.4
String Processing and Regular Expressions
27.5
Viewing Client/Server Environment Variables
27.6
Form Processing and Business Logic
27.7
Server-Side Includes
27.8
Verifying a Username and Password
27.9
Sending E-mail from a Web Browser
27.10 Using ODBC to Connect to a Database
27.11 Cookies and Perl
27.12 Case Study: Building a Search Engine
Based on material  2000 Deitel & Associates, Inc.
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27.1 Common Gateway Interface (CGI)
• Server-side programming
– Process data on the server to increase communication
between clients and servers
– Create interactive applications
• Client-side scripting
– Not always sufficient when building truly interactive Webbased applications
• HyperText Transfer Protocol (HTTP)
– Used for communication between Web browsers and servers
• Universal Resource Locator (URL)
– Used by browsers (clients) to specify name of server from
which to request data
Based on material  2000 Deitel & Associates, Inc.
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27.1 Common Gateway Interface (CGI) (II)
• HTTP GET command
– By issuing command, client directs server to send specific
data to browser
• CGI
– Lets HTTP clients interact with programs across a network
through a Web server
– A standard for interfacing applications with a Web server
– CGI applications
• Can be written in many different programming languages
• Often reside in the directory /cgi-bin
• Within Web server
– Permission granted by webmaster to allow specific
programs to be executed on the server
Based on material  2000 Deitel & Associates, Inc.
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27.1 Common Gateway Interface (CGI) (III)
• Interaction methods
– Standard input (keyboard)
– Standard output (screen)
• Web browser
–
–
–
–
Take info from user
Using HTTP, sends info to a Web server
Server-side CGI program executed
Standard output from server-side applications or scripts
redirected or piped to CGI
– Output sent from CGI over the Internet to client for rendering
• CGI is an interface
– Cannot be directly programmed
– Script or executable program must be used to interact with it
Based on material  2000 Deitel & Associates, Inc.
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27.1 Common Gateway Interface (CGI) (IV)
Data path of a typical CGI-based application
Based on material  2000 Deitel & Associates, Inc.
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27.2 Introduction to Perl
Perl (Practical Extraction and Report Language)
– High-level programming language
– Developed by Larry Wall in 1987
• Trained as a linguist
• A systems admin at NASA
– Rich, easy-to-use text-processing capabilities
– Alternative to the tricky C programming language
– Powerful alternative to Unix shell scripts
• Lots of built-in functionality
• TMTOWTDI
Based on material  2000 Deitel & Associates, Inc.
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27.2 Introduction to Perl
• Current version: Perl 5.006
– Programming Perl (1st ed.) was about Perl 4
– Perl 5 is a complete rewrite
– An entirely new language
• Good choice for programming server side WWW
– Most popular language for doing so today
– Is under continuous update by the online Perl community
Stays competitive with newer server-side technologies
Programmer driven
Extensible by modular objects
Can even search the online object-base to find newer versions
Based on material  2000 Deitel & Associates, Inc.
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27.2 Introduction to Perl (II)
• Perl initially developed for Unix platform
– Always intended to be a cross-platform computer language
• ActivePerl
– Version of Perl for Windows
– Free download at http://www.activestate.com
– Includes the core Perl package
• Predefined functionality expected to behave the same across all platforms
• Perl Interpreter — perl.exe — placed in bin directory
Loaded into memory each time Perl program invoked
– Extension of Perl programs is .pl
Associated with Perl interpreter by default
• Perl program execution
– Type perl –w followed by filename of Perl source code at
command line (Unix or DOS prompt)
Based on material  2000 Deitel & Associates, Inc.
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27.2 Introduction to Perl (III)
Perl command line switches (case sensitive)
Comma nd-line Description
switch
-e ’command’
-S
-U
-v
-w
-h
Interpret one line of Perl code
Search for the specified script using the PATH environment variable
Allow unsafe operations to be executed
Print the version of Perl
Allow warnings to be displayed on compilation of the script
Display all options for perl
Based on material  2000 Deitel & Associates, Inc.
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27.2 Introduction to Perl (IV)
• Comment character - #
– Goes at beginning of every line with comment
• Function print
– Outputs text indicated by quotation marks (“…”)
• Escape sequences
– E.g. \n, \t, \a
– Newline, tab, alert
• Statements terminated with semicolons (;)
– Exception: where braces ({}) used to denote block of code
Based on material  2000 Deitel & Associates, Inc.
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# Fig. 27.4: first.pl
# A first program in Perl.
Outline
print "Welcome to Perl!\n";
1.1 Print Statement
Welcome to Perl!
 2000 Deitel & Associates, Inc. All rights reserved.
12
27.2 Introduction to Perl (V)
• Perl contains set of data types
– Represent different kinds of information
– Each variable name has special character preceding it
• $ - variable contains scalar value
– Strings, integer numbers and floating-point numbers
• @ - indexed array
– Uses an integer (called an index) to reference array elements
• % - hash (associative array)
– Uses keys that are strings to reference individual array elements
– Variables should be initialized before being used
• Variable names in strings
– Serve as place-holders for values they represent
– If have no declared value – set to undef (empty) value
Based on material  2000 Deitel & Associates, Inc.
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# Fig. 27.6: variable.pl
# Program to illustrate the use of scalar variables.
# using a variable in the context of a string
print "Using a variable before initializing: $var\n";
# using a variable in a numeric context
$test = $num + 5;
print "Adding uninitialized variable num to 5 yields: $test.\n";
$a = 5;
print "The value of variable a is: $a\n";
Outline
1.1 Demonstrate
variable in string
before initialization
1.2 Demonstrate
addition involving
variable using print
statements
$a = $a + 5;
print "Variable a after adding 5 is $a.\n";
$b = "A string value";
$a = $a + $b;
print "Adding a string to an integer yields: $a\n";
$number = 7;
$b = $b + $number;
print "Adding an integer to a string yields: $b\n";
Using a variable before initializing:
Adding uninitialized variable num to 5 yields: 5.
The value of variable a is: 5
Variable a after adding 5 is 10.
Adding a string to an integer yields: 10
Adding
an integer
to Inc.
a string
 2000 Deitel
& Associates,
All rights yields:
reserved. 7
1.3 Add integer to
string and print result
Add integer to string
and print result
14
27.2 Introduction to Perl (VI)
• Perl can store arrays
– Arrays divided into elements
• Each can contain an individual scalar variable
• Array definition
@arrayName = (“element1”, “element2”, …,
“elementN”);
• First array element is [0]
– Just like C, C++, etc.
– Could be changed in Perl 4 but should not in Perl 5
Based on material  2000 Deitel & Associates, Inc.
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27.2 Introduction to Perl (VII)
• Arrays
– Elements are referenced as scalar values with element
number in square brackets ([])
• @ refers to array as a whole, $ refers to elements
Example: $array[2]
• Refers to the third element in @array
• Range Operator – “..”
– Used to store all values between given arguments
Example: @array2 = (A..Z);
– Creates array @array2 containing all capital letters in alphabet (all
letters between A and Z)
Based on material  2000 Deitel & Associates, Inc.
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# Fig. 27.7: arrays.pl
# Program to demonstrate arrays in Perl
@array = ("Bill", "Bobby", "Sue", "Michelle");
print "The array contains:\n\n";
print "@array \n\n";
print "Third element: $array[2]\n\n";
@array2 = (A..Z);
print "The range operator is used to store all\n";
print "letters from capital A to Z:\n\n";
print "@array2 \n";
Outline
1.1 Define array
@array
2.1 Print contents of
@array
2.2 Print third element
of @array
3.1 Define array
@array2
The array contains:
Bill Bobby Sue Michelle
Third element: Sue
The range operator is used to store all
letters from capital A to Z:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
 2000 Deitel & Associates, Inc. All rights reserved.
3.2 Explain and print
contents of @array2
17
27.2 Introduction to Perl (VIII)
• In addition to core Perl package
– Add-ons called packages provide additional functionality
• Packages
– Often provide platform specific features
– Are available at
http://www.cpan.org
http://www.activestate.com/packages
Based on material  2000 Deitel & Associates, Inc.
18
27.3 Configuring Personal Web Server (PWS) for
Perl/CGI
• To run CGI with PWS
– Several modifications must be made in the Windows Registry
• PWS must be enabled to execute Perl scripts – does not by default
• For detailed instructions on procedure to update
Windows Registry to handle Perl scripts
– See section 27.3 in Deitel, et al.
Based on material  2000 Deitel & Associates, Inc.
19
27.4 String Processing and Regular Expressions
• Processing textual data easily and efficiently
– One of Perl’s most powerful capabilities
– Usually done through use of regular expressions
• Patterns of characters used to search through text files and databases
• Allows large amounts of text to be searched using relatively simple
expressions
• eq equality operator
– Tests whether two strings are equivalent
example: if ($hello eq “Good Morning”)…
• Keyword my
– Designates variable only valid for block of code in which it is
declared
Based on material  2000 Deitel & Associates, Inc.
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# Fig. 27.16: equals.pl
# Program to demonstrate the eq operator
my $stringa = "Test";
my $stringb = "Testing";
if ($stringa eq "Test")
{
print "$stringa matches Test.\n";
}
else
{
print "$stringa does not match Test.\n";
}
if ($stringb eq "Test")
{
print "$stringb matches Test.\n";
}
else
{
print "$stringb does not match Test.\n";
}
Test matches Test.
Testing does not match Test.
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
1.1 Declare variables
using my
2.1 Test string
variable-string
equality
2.2 Print appropriate
result
3.1 Test second
variable
3.2 Print appropriate
result
21
27.4 my and local
• Keyword my
– Designates variable only valid for block of code in which it is
declared
– In Perl 4 was done by local
• my creates local variables
• local creates local copy & then restores it on exit
• See program …
Based on material  2000 Deitel & Associates, Inc.
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my and local (program)
$lo = 'global';
$m = ‘global';
A();
sub A {
local $lo = 'string';
my
$m = 'string';
B();
}
sub B {
print "B can", ($lo eq 'string' ?'can' :'cannot'),
" see the value of lo set by A.\n";
print "B can", ($m eq 'string' ?'can' :'cannot'),
" see the value of m set by A.\n";
}
------------------------------------------------------------B can see the value of lo set by A.
B cannot see the value of m set by A.
Based on material  2000 Deitel & Associates, Inc.
27.4 String Processing and Regular Expressions
(II)
• eq operator
– Cannot be used to search through a series of words
• Matching ‘operator’ : =~
– Tests whether match for a string is found within a single
string or series of words
• Format
$search =~ /Test/
• Searches for word test within indicate string
Based on material  2000 Deitel & Associates, Inc.
23
27.4 String Processing and Regular Expressions
(III)
• Some meta/modifying characters
–
–
–
–
^ - indicates beginning of a line
$ - indicates end of a line
\b…\b – indicates word boundary
\w – matches any alphanumeric character
• Other modifying characters
Modifying
Character
Purpose
/g
/i
/m
Search everywhere for the expression (global search).
Ignores the case of the search string.
The string is evaluated as if it had multiple lines (i.e., contains
multiple newline characters) of text.
Ignore the newline character and treat it as whitespace. The text
is seen as a single line.
All whitespace characters are ignored when searching the string.
/s
/x
Based on material  2000 Deitel & Associates, Inc.
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# Fig 27.17: expression1.pl
# searches using the matching operator and regular expressions
Outline
$search = "Testing pattern matches";
if ( $search =~ /Test/ )
{
print "Test was found.\n";
}
if ( $search =~ /^Test/ )
{
print "Test was found at the beginning of the line.\n";
}
if ( $search =~ /Test$/ )
{
print "Test was found at the end of the line.\n";
}
if ( $search =~ / \b ( \w+ es ) \b /x )
{
print "Word ending in es: $1 \n";
}
Test was found.
Test was found at the beginning of the line.
Word ending in es: matches
 2000 Deitel & Associates, Inc. All rights reserved.
1.1 Test for word ‘Test’
in string, print result
2.1 Test for word ‘Test’
at beginning on string,
print result
3.1 Test for word ‘Test’
at end of string, print
result
4.1 Test for word in
string ending with
letters ‘es’, print result
27.5 Viewing Client/Server Environment
Variables
• Knowing info about client very useful to system
administrators
• CGI environment variables
– Contains info about client
•
•
•
•
Web browser being used
Version of CGI server running
HTTP host, HTTP connection
Much more
• use statement
– Allows inclusion of predefined library packages in programs
Based on material  2000 Deitel & Associates, Inc.
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27.5 Viewing Client/Server Environment
Variables (II)
27
• CGI Library
– Included to provide functionality that makes it easier to write HTML sent to
Web browser
– Contains keywords that represent HTML tags
• foreach loop
– Iterates through keys in given hashtable, performs indicated actions
foreach $key (sort keys %ENV)
– Iterates through %ENV hashtable
• Built-in table in Perl that contains names and values of all CGI
environment variables
– sort function
• returns list in alphabetical order
– Assigns current key to $key and performs indicated actions
Based on material  2000 Deitel & Associates, Inc.
1
# Fig. 27.19: environment.pl
2
# Program to display CGI environment variables
3
use CGI qw/:standard/;
1.1 use standard CGI
library
4
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print header;
6
print "<HTML>";
7 print "
8
print "
9
print "
<HEAD>";
<TITLE>Environment Variables...</TITLE>";
2.1 Print top of HTML
Table
</HEAD>";
10 print "
<BODY TEXT = BLACK BGCOLOR = WHITE>";
11 print "
<BASEFONT FACE = \"ARIAL,SANS-SERIF\" SIZE = 2>";
12 print "
<TABLE BORDER = 0 CELLPADDING = 2 CELLSPACING = 0";
13 print "
Outline
WIDTH = 100%>";
14
3.1 Use foreach
function to sort
through keys in %ENV
hashtable
15 foreach $key (sort keys %ENV)
16 {
17
print "<TR>";
18
print "<TD BGCOLOR = #11BBFF><STRONG>$key</STRONG></TD>";
19
print "<TD><FONT COLOR = BLACK SIZE = 2>$ENV{$key}";
20
print "</Font></TD>";
21
print "</TR>";
22 }
23
24 print "
25 print "
</TABLE>";
</BODY>";
26
 2000
print
Deitel
"</HTML>";
& Associates, Inc. All rights reserved.
3.2 Print current keys
in table
4.1 Close table
29
Script Output
Based on material  2000 Deitel & Associates, Inc.
30
27.6 Form Processing and Business Logic
• HTML FORMs
1. Allow users to enter data
2. Data sent to Web server for processing
3. Program processes data
– Allows users to interact with server
– Vital to electronic commerce
• FORM element
– Indicates what action should occur when user submits form
– Attribute: ACTION = “cgi-bin/form.pl”
• Directs server to execute form.pl Perl script
Based on material  2000 Deitel & Associates, Inc.
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- Fig. 27.20: form.html -->
3
4<HTML>
5<HEAD>
6<TITLE>Sample FORM to take user input in HTML</TITLE>
7</HEAD>
8
9<BODY BACKGROUND = "images/back.gif">
10<BASEFONT FACE = "ARIAL,SANS-SERIF" SIZE = 2>
11
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<FONT SIZE = +2>
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<STRONG>This is a sample registation form.</STRONG>
14
</FONT><BR>
15
Please fill in all fields and click Register.
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<FORM METHOD = "POST" ACTION = "/cgi-bin/form.pl">
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<IMG SRC = "images/user.gif"><BR>
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<FONT COLOR = BLUE>
20
Please fill out the fields below.<BR>
21
</FONT>
22
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<IMG SRC = "images/fname.gif">
24
<INPUT TYPE = "TEXT" NAME = "FNAME"><BR>
25
<IMG SRC = "images/lname.gif">
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<INPUT TYPE = "TEXT" NAME = "LNAME"><BR>
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<IMG SRC = "images/email.gif">
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<INPUT TYPE = "TEXT" NAME = "EMAIL"><BR>
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<IMG SRC = "images/phone.gif">
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<INPUT TYPE = "TEXT" NAME = "PHONE"><BR>
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<FONT SIZE=-2>
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Must be in the form (555)555-5555<BR><BR>
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</FONT>

2000
Deitel
& Associates, Inc. All rights reserved.
35
Outline
1.1 Open FORM
1.2 Define FORM
attributes
1.3 Insert and define
form INPUT elements
1.4 Specify correct
input format
36
<IMG SRC = "images/downloads.gif"><BR>
37
<FONT COLOR = BLUE>
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Which book would you like information about?<BR>
39
</FONT>
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<SELECT NAME = "BOOK">
42
<OPTION>Internet and WWW How to Program
43
<OPTION>C++ How to Program 2e
44
<OPTION>Java How to Program 3e
45
<OPTION>Visual Basic How to Program 1e
46
</SELECT>
47
<BR><BR>
48
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<IMG SRC = "images/os.gif"><BR>
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<FONT COLOR = BLUE>
51
Which operating system are you
52
currently using?<BR>
53
</FONT>
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<INPUT TYPE = "RADIO" NAME = "OS" VALUE = "Windows NT"
56
CHECKED>
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Windows NT
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<INPUT TYPE = "RADIO" NAME = "OS" VALUE = "Windows 95">
59
Windows 95
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<INPUT TYPE = "RADIO" NAME = "OS" VALUE = "Windows 98">
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Windows 98<BR>
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<INPUT TYPE = "RADIO" NAME = "OS" VALUE = "Linux">
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Linux
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<INPUT TYPE = "RADIO" NAME = "OS" VALUE = "Other">
65
Other<BR>
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<INPUT TYPE = "SUBMIT" VALUE = "Register">
67
</FORM>
68</BODY>
 2000 Deitel & Associates, Inc. All rights reserved.
69</HTML>
Outline
1.5 Continue inserting
and defining form
INPUT element
1.6 Close FORM
element
33
Script Output
Based on material  2000 Deitel & Associates, Inc.
34
27.6 Form Processing and Business Logic (II)
• Retrieving data from form output
– Assign to variables
– Example: Assign data from form INPUT OS to variable $OS
$os = param(OS);
• Testing for correct form input
– Example: Make sure phone number in format (555)555-5555
if ( $phone =~ / \( \d{3} \) \d{3} - \d{3} /x) { actions }
– d{n} tests for n characters
– \ is escape character
• Close-bracket (“)”) character is used in Perl statements, needs escape
character “\” to appear as part of search test string
Based on material  2000 Deitel & Associates, Inc.
1 # Fig. 27.21: form.pl
2 # Program to read information sent to the server
3 # from the FORM in the form.html document.
4
5 use CGI qw/:standard/;
6
7 $os = param(OS);
8 $firstname = param(FNAME);
9 $lastname = param(LNAME);
10 $email = param(EMAIL);
11 $phone = param(PHONE);
12 $book = param(BOOK);
13
14 print header;
15 print "<BODY BACKGROUND = \"/images/back.gif\">";
16 print "<BASEFONT FACE = \"ARIAL,SANS-SERIF\" SIZE = 3>";
17
18 if ( $phone =~ / \( \d{3} \) \d{3} - \d{4} /x )
19 {
20
print "Hi <FONT COLOR = BLUE><B>$firstname</B></FONT>";
21
print ". Thank you for completing the survey.<BR>";
22
print "You have been added to the ";
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print "<FONT COLOR = BLUE><STRONG>$book </STRONG></FONT>";
24
print "mailing list.<BR><BR>";
25
print "<STRONG>The following information has been saved ";
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print "in our database:</STRONG><BR>";
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print "<TABLE BORDER = 0 CELLPADDING = 0";
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print "
CELLSPACING = 10>";
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print "<TR><TD BGCOLOR = #FFFFAA>Name </TD>";
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print "
<TD BGCOLOR = #FFFFBB>Email</TD>";
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print "
<TD BGCOLOR = #FFFFCC>Phone</TD>";

2000
Deitel
&
Associates,
All rights= reserved.
32
print "
<TD Inc.
BGCOLOR
#FFFFDD>OS</TD></TR>";
Outline
1.1 use standard CGI
library
2.1 Assign form field
values to variables
3.1 Test for correct
phone number input
form using if
structure
3.2 Indicate actions to
be performed if test
returns TRUE result
33
print "<TR><TD>$firstname $lastname</TD><TD>$email</TD>";
34
print "<TD>$phone</TD><TD>$os</TD></TR>";
35
print "</TABLE>";
36
print "<BR><BR><BR>";
37
print "<CENTER><FONT SIZE = -3>";
38
print "This is only a sample form. ";
39
print "You have not been added to a mailing list.";
40
print "</FONT></CENTER>";
41 }
42 else
43 {
44
print "<FONT COLOR = RED SIZE = +2>";
45
print "INVALID PHONE NUMBER</FONT><BR>";
46
print " A valid phone number must be in the form";
47
print "<STRONG>(555)555-5555</STRONG>";
48
print "<FONT COLOR = BLUE> Click the Back button, ";
49
print "enter a valid phone number and resubmit.<BR><BR>";
50
print "Thank You.";
51 }
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
3.3 Finish inputting if
structure actions and
close structure
4.1 Set actions to be
performed if if
structure returns a
FALSE value
37
Script Output 1
Based on material  2000 Deitel & Associates, Inc.
38
Script Output 2
Based on material  2000 Deitel & Associates, Inc.
39
27.7 Server-Side Includes
• Web offers ability to track
– Where client coming from
– What client views on your site
– Where client goes after your site
• Tracking Web data important, allows Web masters to
– Know which sites visited most frequently
– Know how effective advertisements and products are
• Server-side includes (SSIs)
– Commands embedded in HTML documents
– Provide for content creation
– Allow inclusion of current time, date or even contents of
different html document
Based on material  2000 Deitel & Associates, Inc.
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27.7 Server-Side Includes (II)
• SSI commands
– Execute CGI scripts on a server
– Are capable of connecting to an ODBC data source
• Use to create customized Web pages depending for certain conditions
– Document containing SSI commands has .shtml file
extension
• EXEC CGI command
– Issued to execute a Perl script before document sent to client
Example: <!-- #EXEX CGI=“cgi-bin/counter.pl” -->
– Executes the Perl script counter.pl, located in the cgibin directory
Based on material  2000 Deitel & Associates, Inc.
41
27.7 Server-Side Includes (III)
• ECHO command
– Used to display variable information
– Is followed by the keyword VAR and variable’s constant name
Example: <!-- #ECHO VAR=“DATE_LOCAL” -->
– Returns the current local time
• Other variables
– DATE_GMT
• Contains current Greenwich Mean Time
– DOCUMENT_NAME
• Contains name of current document
– Many more
Based on material  2000 Deitel & Associates, Inc.
42
27.7 Server-Side Includes (IV)
• Perl scripts can access and modify other files
– open() function
• Form: open(fileHandle, “>fileName”);
– > discards any data in file, creates new file if does not exist
– >> append mode
– While file open, referenced using fileHandle
– Close file using the close() statement
• Format: close(fileHandle);
– print statement can redirect output to a file
print COUNTWRITE $data;
• Assigns $data to file pointed to by COUNTWRITE
• If the file is open for writing already
Based on material  2000 Deitel & Associates, Inc.
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27.7 Server-Side Includes (V)
• length() function
– Returns length of string
• substr( expr, len, offset ) function
– Similar to JavaScript’s substr function
– First argument (expr)
• Specifies string from which to take a substring
– Second argument (offset)
• Specifies offset in characters from beginning of the string
– Third argument (len)
• Specifies length of substring to return
Based on material  2000 Deitel & Associates, Inc.
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- Fig. 27.22 counter.shtml -->
3
4<HTML>
5
<HEAD>
6
<TITLE>Using Server Side Includes</TITLE>
7
</HEAD>
8
9<BODY>
10
<CENTER>
11
<H3> Using Server Side Includes</H3>
12
</CENTER>
13
14
<!-- #EXEC CGI="/cgi-bin/counter.pl" --><BR>
15
The Greenwich Mean Date is
16
<FONT COLOR = BLUE>
17
18
<!-- #ECHO VAR="DATE_GMT" -->.
19
</FONT><BR>
20
The name of this document is
21
<FONT COLOR = BLUE>
22
23
<!-- #ECHO VAR="DOCUMENT_NAME" -->
24
</FONT><BR>
25
The local date is
26
<FONT COLOR = BLUE>
27
28
<!-- #ECHO VAR="DATE_LOCAL" -->
29
</FONT><BR>
30
This document was last modified on
31
<FONT COLOR = BLUE>

2000
Deitel & Associates, Inc. All rights reserved.
32
Outline
1.1 Execute Perl script
counter.pl using
EXEC CGI statement
2.1 Use ECHO VAR
statements to display
environmental
variables
33
<!-- #ECHO VAR="LAST_MODIFIED" -->
34
</FONT><BR>
35
Your current IP Address is
36
<FONT COLOR = BLUE>
37
38
<!-- #ECHO VAR="REMOTE_ADDR" -->
39
</FONT><BR>
40
My server name is
41
<FONT COLOR = BLUE>
42
43
<!-- #ECHO VAR="SERVER_NAME" -->
44
</FONT><BR>
45
And I am using the
46
<FONT COLOR = BLUE>
47
48
<!-- #ECHO VAR="SERVER_SOFTWARE" -->
49
Web Server.</FONT><BR>
50
You are using
51
<FONT COLOR = BLUE>
52
53
<!-- #ECHO VAR="HTTP_USER_AGENT" -->.
54
</FONT><BR>
55
This server is using <FONT COLOR = BLUE>
56
57
<!-- #ECHO VAR="GATEWAY_INTERFACE" -->.
58
</FONT><BR>
59
<BR><BR>
60
<CENTER>
61
<HR>
62
<FONT SIZE = -5>This document was last modified on
63
64
<!-- #ECHO VAR="LAST_MODIFIED" --></FONT>
65
66
</CENTER>
67</BODY>
 2000 Deitel & Associates, Inc. All rights reserved.
68</HTML>
Outline
2.2 Continue printing
environmental
variables using ECHO
VAR statements
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
# Counter.pl
# Program to track the number of times a web page
# has been accessed.
Outline
open(COUNTREAD, "counter.dat");
my $data = <COUNTREAD>;
$data++;
close(COUNTREAD);
1.1 Open
counter.dat, assign
to filehandle
COUNTREAD
open(COUNTWRITE, ">counter.dat");
print COUNTWRITE $data;
close(COUNTWRITE);
1.2 Increment data in
COUNTREAD
print "<CENTER>";
print "<STRONG>You are visitor number</STRONG><BR>";
1.3 Close COUNTREAD
for ($count = 0; $count < length($data);$count++)
{
$number = substr( $data, $count, 1 );
print "<IMG SRC=\"images/counter/$number.jpg\">";
}
2.1 Assign data
contained in file
counter.dat to
variable $data
print "</CENTER>";
3.1 Use for structure
to output number of
page hits using
number images
 2000 Deitel & Associates, Inc. All rights reserved.
47
Script Output
Based on material  2000 Deitel & Associates, Inc.
48
27.8 Verifying a Username and Password
• Often desirable to have private Web site
– Developers often employ username and password
authentication to implement privacy
• Upcoming files
– verify.html – HTML document client browser displays
– password.pl – Perl script that verifies username and
password inputted by client and performs appropriate actions
– data.txt – Text file containing username and password
combinations (unencrypted for simplicity)
Based on material  2000 Deitel & Associates, Inc.
49
27.8 Verifying a Username and Password (II)
• If file cannot be opened
– Use function die to exit program and print message
• while <fileHandle>
– Executes structure while still information in fileHandle
• split function
– Read contents of a file into an array
@arrayName = split(/\n/)
– Creates array arrayName, creates new array entry after every \n
character
• Access array elements and split into two parts
foreach $entry (@data) {…}
– Performs indicated action on every entry in array @data
– Subsequently assigns entry information to $entry
Based on material  2000 Deitel & Associates, Inc.
50
27.8 Verifying a Username and Password (III)
• Split array into two parts
($name, $pass) = split(/,/, $entry)
– Assigns username string of current entry to $name
– Assigns password string of current entry to $pass
Based on material  2000 Deitel & Associates, Inc.
51
27.8 Verifying a Username and Password (III)
• Perl has logical and (&&) and or (||) operators
– Same format as other languages
Example:
if ($userverified && $passwordverified) {…}
– Evaluates to true if both variable values are true
– Short-circuit evaluation
• String context: true is any non-empty string
• Numeric context: true is any non-zero number
• String "0" is false!
Based on material  2000 Deitel & Associates, Inc.
52
27.8 Verifying a Username and Password (III)
sub functionName {…}
– Sets actions of user-defined function functionName
– User-defined functions accessed: &functionName
Based on material  2000 Deitel & Associates, Inc.
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- Fig. 27.24: verify.html -->
3
4<HTML>
5<HEAD>
6<TITLE>Verifying a username and a password.</TITLE>
7</HEAD>
8
9<BODY BACKGROUND = "images/back.gif">
10
<P>
11
<FONT FACE = Arial>
12
Type in your username and password below.
13
</FONT><BR>
14
<FONT COLOR = #0000FF FACE = Arial SIZE = 1>
15
<STRONG>
16
Note that password will be sent as plain text
17
</STRONG>
18
</FONT>
19
</P>
20
21
<FORM ACTION = "/cgi-bin/password.pl" METHOD = "post">
22
<BR>
23
24
<TABLE BORDER = "0" CELLSPACING = "0" STYLE = "HEIGHT: 90px;
25
WIDTH: 123px" CELLPADING = "0">
26
<TR>
27
<TD BGCOLOR = #DDDDDD COLSPAN = 3>
28
<FONT FACE = Arial SIZE = 2>
29
<STRONG>Username:</STRONG>
30
</FONT>
31
</TD>

2000
Deitel
&
32
</TR>Associates, Inc. All rights reserved.
Outline
1.1 Print instructions
2.1 Open FORM and
define ACTION
attribute
3.1 Open HTML TABLE
33
<TR>
34
<TD BGCOLOR = #DDDDDD COLSPAN = 3>
35
<INPUT SIZE = "40" NAME = "USERNAME"
36
37
STYLE = "HEIGHT: 22px; WIDTH: 115px">
</TD>
38
</TR>
39
<TR>
40
<TD BGCOLOR = #DDDDDD COLSPAN = 3>
41
<FONT FACE = Arial SIZE = 2>
42
<STRONG>Password:</STRONG>
43
</FONT></TD>
44
</TR>
45
<TR>
46
<TD BGCOLOR = #DDDDDD COLSPAN = 3>
47
<INPUT SIZE = "40" NAME = "PASSWORD"
48
STYLE = "HEIGHT: 22px; WIDTH: 115px"
49
TYPE = PASSWORD>
50
<BR></TD>
51
</TR>
52
<TR>
53
<TD COLSPAN = 3>
54
<INPUT TYPE = "submit" VALUE = "Enter"
55
56
STYLE = "HEIGHT: 23px; WIDTH: 47px">
</TD>
57
</TR>
58
</TABLE>
59
</FORM>
60</BODY>
 2000 Deitel & Associates, Inc. All rights reserved.
61</HTML>
Outline
3.2 Insert and define
INPUT elements for
username and
password
3.3 Insert INPUT
submit button
3.4 Close TABLE and
FORM elements
55
Script Output
Based on material  2000 Deitel & Associates, Inc.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
# Fig. 27.25: password.pl
# Program to search a database for usernames and passwords.
use CGI qw/:standard/;
my $username = param(USERNAME);
my $password = param(PASSWORD);
open(FILE, "data.txt") ||
die "The database could not be opened";
while(<FILE>)
{
@data = split(/\n/);
foreach $entry (@data)
{
($name, $pass) = split(/,/, $entry);
if($name eq "$username")
{
$userverified = 1;
if ($pass eq "$password")
{
$passwordverified = 1;
}
}
}
}
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
1.1 Open data.txt
and assign to FILE
1.2 Enter text to be
printed if the file
cannot be accessed
using die function
2.1 Open while
structure
3.1 Create @data array
using FILE
3.2 Split each entry
into NAME and PASS
entries
3.3 Use if structure to
verify username and
password and perform
appropriate actions
30
close(FILE);
31
32
if ($userverified && $passwordverified)
33
{
34
&accessgranted;
35
}
36
elsif ($userverified && !$passwordverified)
37
{
38
&wrongpassword;
39
}
40
else
41
{
42
&accessdenied;
43
}
44
45 sub accessgranted
46 {
47
print header;
48
print "<TITLE>Thank You</TITLE>";
49
print "<FONT FACE = Arial SIZE = 2 COLOR = BLUE>";
50
print "<STRONG>Permission has been granted $username.";
51
print "<BR> Enjoy the site.</STRONG></FONT>";
52 }
53
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
3.4 Close while
structure
4.1 Use if structures
to call user-defined
programs depending
on outcome of
password verification
5.1 Define
accessgranted
function
5.2 Print ‘permission
granted’ message
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
sub wrongpassword
{
print header;
print "<TITLE>Access Denied</TITLE>";
print "<FONT FACE=Arial SIZE=2 COLOR=Red><STRONG>";
print "You entered an invalid password.<br> ";
print "Access has been denied.</STRONG></FONT>";
exit;
}
sub accessdenied
{
print header;
print "<TITLE>Access Denied</TITLE>";
print "<FONT FACE=Arial SIZE=3 COLOR=Red><STRONG>";
print "You were denied access to this server.";
print "</STRONG></FONT>";
exit;
}
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
6.1 Define
wrongpassword
function
6.2 Print ‘invalid
password’ message
7.1 Define
accessdenied
function
7.2 Print ‘access
denied’ message
1
account1,password1
2
account2,password2
Outline
3 account3,password3
4
account4,password4
5
account5,password5
6
account6,password6
7
account7,password7
8
account8,password8
9
account9,password9
10 account10,password10
Data.txt
1.1 Input username
and password
combinations using
format:
username,password/n
 2000 Deitel & Associates, Inc. All rights reserved.
60
Script Output
Based on material  2000 Deitel & Associates, Inc.
61
27.9 Sending E-Mail From a Web Browser
• Email
– One of most frequently used capabilities of the Internet
– Can be sent directly from browser using Perl script
• Net package’s Simple Mail Transfer Protocol (SMTP)
– Use this SMTP functionality to send email
code: use Net::SMTP;
• Email cannot be sent without a valid smtp server
– Server name client uses is usually text after the”@” in your
client’s email address
Based on material  2000 Deitel & Associates, Inc.
62
27.9 Sending E-Mail From a Web Browser
• Create a new instance of a mail server object
smtp = Net::SMTP->new($mailserver);
• -> is Perl’s scope operator
– Equivalent to “.” in JavaScript
• datasend function
– Tells mail server that a command is being issued
• smtp->quit;
– Closes connection to smtp server
Based on material  2000 Deitel & Associates, Inc.
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- Fig. 27.27: email.html -->
3<HTML>
4<HEAD>
5
<TITLE>Web-based email interface.</TITLE>
6</HEAD>
7
8<BODY BACKGROUND = "images/back.gif">
9
<FORM ACTION = "cgi-bin/mail.pl" METHOD = "POST">
10
<TABLE BORDER = "0" CELLSPACING = "0" CELLPADING = "0">
11
12
<TR>
13
<TD BGCOLOR = #DDDDDD COLSPAN = 3>
14
<INPUT SRC = "images/send.gif" TYPE = "IMAGE">
15
<IMG SRC = "images/bar.gif">
16
</TD>
17
</TR>
18
19
<TR>
20
<TD BGCOLOR = #DDDDDD WIDTH = "10%"><STRONG>
21
<FONT FACE = "Arial" SIZE = "2">To:&nbsp;</FONT>
22
</STRONG>
23
</TD>
24
<TD BGCOLOR = #DDDDDD><INPUT NAME = "TO">
25
</TD>
26
</TR>
27
28
<TR>
29
<TD BGCOLOR = #DDDDDD>
30
<P><FONT FACE = Arial SIZE = 2>
31
<STRONG>From:</STRONG>

2000
Deitel
&
Associates, Inc. All rights reserved.
32
</FONT></P>
Outline
1.1 Open FORM and
define ACTION
attribute
2.1 Inset and define
INPUT submit image
2.2 Insert text
INPUTs for other email
field categories
33
</TD>
34
<TD BGCOLOR = #DDDDDD><INPUT NAME = "FROM">
35
</TD>
36
</TR>
37
38
<TR>
39
<TD BGCOLOR = #DDDDDD>
40
<P><FONT FACE = Arial SIZE = 2>
41
<STRONG>Subject:</STRONG>
42
</FONT></P>
43
</TD>
44
<TD BGCOLOR = #DDDDDD><INPUT NAME = "SUBJECT">
45
</TD>
46
</TR>
47
48
<TR>
49
<TD BGCOLOR = #DDDDDD>
50
<P><FONT FACE = "Arial" SIZE = 2><STRONG><EM>Mail
51
Server:</EM></STRONG></FONT></P>
52
</TD>
53
<TD BGCOLOR = #DDDDDD><INPUT NAME = "MAILSERVER">
54
</TD>
55
</TR>
56
57
<TR>
58
<TD BGCOLOR = #DDDDDD COLSPAN = 3>
59
<P>
60
<STRONG><FONT FACE = "Arial" SIZE = "2"><BR>Message:
61
</FONT>
62
</STRONG><BR>
63
<TEXTAREA COLS = 50 NAME = "MESSAGE" ROWS = 6

2000
Deitel
&
Associates,
Inc. All rights
reserved.
64
STYLE
= "HEIGHT:
170px;
WIDTH: 538px"></TEXTAREA>
Outline
2.3 Insert and define
remaining INPUT
elements for email
fields
2.4 Insert and define
TEXTAREA for body of
email message
65
</P><P> </P>
66
</TD>
67
</TR>
68
69
</TABLE>
70
</FORM>
71 </HTML>
Outline
1.1 Close TABLE and
FORM tags
Script Output
 2000 Deitel & Associates, Inc. All rights reserved.
1
# Fig. 27.28: mail.pl
2
# Program to send email from a Web-based form.
Outline
3
4
use Net::SMTP;
5
use CGI qw/:standard/;
1.1 use SMTP
6
7
my $to = param("TO");
8
my $from
9
my $subject
= param("SUBJECT");
10 my $message
= param("MESSAGE");
= param("FROM");
11 my $mailserver = param("MAILSERVER");
12
13 print header;
1.2 use CGI standard
library
2.1 Set local variable
values to user form
inputs
14 print "<H3>The request has been Processed. ";
15 print "Thank You $from</H3>";
16
3.1 print ‘request
processed’ message
17 $smtp = Net::SMTP->new($mailserver);
18
19 $smtp->mail($ENV{USER});
20 $smtp->to("$to");
4.1 Connect to SMTP
server
21 $smtp->data();
22 $smtp->datasend("To: $to \n");
23 $smtp->datasend("From: $from \n");
24 $smtp->datasend("Subject: $subject \n");
25 $smtp->datasend("\n");
26 $smtp->datasend("$message \n");
4.2 Form email
message using
data(), datasend()
and dataend()
functions
27 $smtp->dataend();
28
 2000
Deitel & Associates, Inc. All rights reserved.
29
$smtp->quit;
4.3 quit smtp server
67
Script Output
Based on material  2000 Deitel & Associates, Inc.
68
27.10 Using ODBC to Connect to a Database
• Databases allow companies to
– Enter world of e-commerce
– Maintain crucial data
• Perl package Win32-ODBC
– Enables Perl programs to connect to ODBC data sources
– Data source must first be defined using Data Source Administrator in MS
Windows (see Section 25.5)
• From Web browser
1. Client enters SQL query string
2. String sent to Web server
3. Perl script executed
• Database queried
4. Record set in HTML form sent back to client
Based on material  2000 Deitel & Associates, Inc.
69
27.10 Using ODBC to Connect to a Database (II)
• Script connects to ODBC Data source
– By passing the Data Source Name, $DSN, to the constructor
for the Win32::ODBC object.
$Data = new Win32::ODBC($DSN)
• new specifies that a new instance of the object is to be created
– Win32::ODBC::Error
• Returns error that occurred
• Query string sent to database
$Data->Sql($querystring)
– If fails, error message is returned
Based on material  2000 Deitel & Associates, Inc.
70
27.10 Using ODBC to Connect to a Database (III)
• Method DataHash
– Retrieves the fields in a row from the record set
• Coding HTML in Perl
– Open HTML area with print header;
– Close HTML area with print end_html;
• Use tables to output fields in a database
– Organizes information neatly
Based on material  2000 Deitel & Associates, Inc.
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- Fig. 27.30: data.html -->
Outline
3
4<HTML>
5<HEAD>
6<TITLE>Sample Database Query</TITLE>
1.1 Open and define
FORM
7</HEAD>
8
9<BODY BACKGROUND = "images/back.gif">
10<BASEFONT FACE = "ARIAL,SANS-SERIF" SIZE = 2>
1.2 Insert and define
text INPUT for
entering SQL query
11
12
13
14
<FONT SIZE = +2>
<STRONG>Querying an ODBC database.</STRONG>
</FONT><BR>
15
16
17
<FORM METHOD = "POST" ACTION = "cgi-bin/data.pl">
<INPUT TYPE = "TEXT" NAME = "QUERY" SIZE = 40
18
19
20
VALUE = "SELECT * FROM AUTHORS"><BR><BR>
<INPUT TYPE = "SUBMIT" VALUE = "Send Query">
</FORM>
21</BODY>
22</HTML>
 2000 Deitel & Associates, Inc. All rights reserved.
1.3 Insert INPUT button
72
Script Output
Based on material  2000 Deitel & Associates, Inc.
1 # Fig. 27.31: data.pl
2 # Program to query a database and send
3 # results to the client.
4
5 use Win32::ODBC;
6 use CGI qw/:standard/;
7
8 my $querystring = param(QUERY);
9 $DSN = "Products";
10
11 print header;
12
13 if (!($Data = new Win32::ODBC($DSN)))
14 {
15
print "Error connecting to $DSN\n";
16
print "Error: " . Win32::ODBC::Error() . "\n";
17
exit;
18 }
19
20 if ($Data->Sql($querystring))
21 {
22
print "SQL failed.\n";
23
print "Error: " . $Data->Error() . "\n";
24
$Data->Close();
25
exit;
26 }
27
28 print "<BODY BACKGROUND = \"/images/back.gif\">";
29 print "<BASEFONT FACE = \"ARIAL,SANS-SERIF\" SIZE = 3>";
30 print "<FONT COLOR = BLUE SIZE = 4> Search Results </FONT>";
31
 2000
Deitel & =Associates,
Inc. All rights reserved.
32
$counter
0;
Outline
1.1 use
Win32::ODBC;
1.2 use CGI standard
library
1.3 print header
(open HTML coding)
2.1 Query database
and assign to $Data
and set actions if
query failed
3.1 Assign record set
generated by SQL
statement to $Data
and set error actions
4.1 Initialize counter
variable
33
34 print "<TABLE BORDER = 0 CELLPADDING = 5 CELLSPACING = 0>";
35
36 while($Data->FetchRow())
37 {
38
39
%Data = $Data->DataHash();
40
41
42
print "<TR>";
43
44
45
46
47
48
49
foreach $key( keys( %Data ) )
{
print "<TD BGCOLOR = #9999CC>$Data{$key}</TD>";
}
print "</TR>";
$counter++;
50
51
52
53
54
55
}
print
print
print
print
print
56
57
58
59
60
print "<A href = \"mailto:deitel\@deitel.com\">Deitel ";
print "and Associates, Inc.</A>.";
print end_html;
"</TABLE>";
"<BR>Your search yielded <B>$counter</B> results.";
"<BR><BR>";
"<FONT SIZE = 2>";
"Please email comments to ";
$Data->Close();
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
5.1 Insert records into
array and execute
DataHash
5.2 Use foreach
statement to output
results
5.3 Print number of
results and closing
comments
6.1 print end_html;
(close HTML coding
area)
6.2 Close data source
75
Script Output
Based on material  2000 Deitel & Associates, Inc.
76
27.11 Cookies and Perl
• Cookies
– Used to maintain state information for a particular client
– May contain
• Username
• Password
• Specific information that will be helpful when user return to same site
– Are small text files saved on client’s machine
– Sent back to Web server whenever user requests a Web page
– Can be written to client machines using Perl scripts
Based on material  2000 Deitel & Associates, Inc.
77
27.11 Cookies and Perl (II)
• To set a cookie using Perl
– Set variable values to user input strings
– Set cookie setup info
• $expires – expiration date of cookie
• $path – location on clients computer to store cookie
• $server_domain – IP address of your server
– print “set-cookie: “; …
set information to be stored in cookie using print statement
– Repeat as needed to store all information in cookie
• After cookie written
– Text file added to Temporary Internet Files directory
• Filename: Cookie:[email protected]
Based on material  2000 Deitel & Associates, Inc.
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- Fig. 27.32: cookies.html -->
3
4<HTML>
5
<HEAD>
6
<TITLE>Writing a cookie to the client computer</TITLE>
7
</HEAD>
8
9<BODY BACKGROUND = "images/back.gif">
10<BASEFONT FACE = "ARIAL,SANS-SERIF" SIZE = 2>
11
12
<FONT SIZE = +2>
13
<B>Click Write Cookie to save your cookie data.</B>
14
</FONT><BR>
15
16
<FORM METHOD = "POST" ACTION = "cgi-bin/cookies.pl">
17
<STRONG>Name:</STRONG><BR>
18
<INPUT TYPE = "TEXT" NAME = "NAME"><BR>
19
<STRONG>Height:</STRONG><BR>
20
<INPUT TYPE = "TEXT" NAME = "HEIGHT"><BR>
21
<STRONG>Favorite Color</STRONG><BR>
22
<INPUT TYPE = "TEXT" NAME = "COLOR"><BR>
23
<INPUT TYPE = "SUBMIT" VALUE = "Write Cookie">
24
</FORM>
25</BODY>
26</HTML>
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
1.1 Enter text
instructions
2.1 Open FORM and
define ACTION
attribute
2.2 Insert and define
INPUT fields
2.3 Insert INPUT
submit button
2.4 Close FORM area
79
Script Output
Based on material  2000 Deitel & Associates, Inc.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
# Fig. 27.33: cookies.pl
# Program to write a cookie to a client’s machine
use CGI qw/:standard/;
my $name = param(NAME);
my $height = param(HEIGHT);
my $color = param(COLOR);
$expires = "Monday, 20-Dec-99 16:00:00 GMT";
$path = "";
$server_domain = "127.0.0.1";
print "Set-Cookie: ";
print "Name", "=", $name, "; expires=", $expires,
"; path=", $path, "; domain=", $server_domain, "\n";
print "Set-Cookie: ";
print "Height", "=", $height, "; expires=", $expires,
"; path=", $path, "; domain=", $server_domain, "\n";
print "Set-Cookie: ";
print "Color", "=", $color, "; expires=", $expires,
"; path=", $path, "; domain=", $server_domain, "\n";
print header;
print "<BODY BACKGROUND = \"/images/back.gif\">";
print "<BASEFONT FACE = \"ARIAL,SANS-SERIF\" SIZE = 3>";
print "The cookie has been set with the folowing data:";
print "<BR><BR>";
print "<FONT COLOR=BLUE>Name:</FONT> $name <BR>";
print "<FONT COLOR = BLUE>Height:</FONT> $height<BR>";
print "<FONT COLOR = BLUE>Favorite Color:</FONT> ";
print "<FONT COLOR = $color> $color<BR>";
 2000 Deitel & Associates, Inc. All rights reserved.
Outline
81
Script Output
Based on material  2000 Deitel & Associates, Inc.
82
27.11 Cookies and Perl (III)
• Cookies are read from client machine using Perl
– Function &readCookies returns the information stored in
cookies sent to client from server ip address
• Information read with statement
$ENV{‘HTTP_COOKIE’}
– Cookie information can be read by
• Storing information in hash array
• Splitting fields
• Displaying information
• Display cookie output in table for organization
Based on material  2000 Deitel & Associates, Inc.
1
2
3
4
5
6
7
8
9
# Fig. 27.36: read_cookies.pl
# Program to read cookies from the client’s computer
use CGI qw/:standard/;
print
print
print
print
header;
"<BODY BACKGROUND = \"/images/back.gif\">";
"<BASEFONT FACE = \"ARIAL,SANS-SERIF\" SIZE = 3>";
"<STRONG>The following data is saved in a cookie on your ";
10 print "computer.</STRONG><BR><BR>";
11
12 my %cookie = &readCookies;
13
14 print ("<TABLE ",
15
"BORDER = \"5\" ",
16
"CELLSPACING = \"0\" ",
17
"CELLPADDING = \"10\">");
18
19 foreach $cookie_name (keys %cookie)
20 {
21
print "<TR>";
22
print "
<TD BGCOLOR=#AAAAFF>$cookie_name</TD>";
23
print "
<TD BGCOLOR=#AAAAAA>$cookie{$cookie_name}</TD>";
24
print "</TR>";
25 }
26 print "</TABLE>";
27
28 sub readCookies
29 {
30
my @cookie_values = split (/; /,$ENV{’HTTP_COOKIE’});
31
 2000 foreach
Deitel & Associates,
Inc. All rights reserved.
32
(@cookie_values)
Outline
1.1 use CGI
standard library
1.2 print header
2.1 Call function
readCookies to and
store info in %cookie
3.1 Use foreach
structure to output
cookie info
4.1 Define function
readCookies
4.2 Put cookie
information into an
array
33
34
35
{
36
37
38
39 }
}
my ($cookie_name, $cookie_value) = split ( /=/, $_ );
$cookies{$cookie_name} = $cookie_value;
return %cookies;
Outline
4.3 Split cookie entry
names and values
4.4 Return information
for output
 2000 Deitel & Associates, Inc. All rights reserved.
85
Script Output
Based on material  2000 Deitel & Associates, Inc.
86
27.12 Case Study: Building a Search Engine
• Search engines
– Allow clients to search through catalogs of info for data
• Typical search process
1. Usually, search string entered by client using Web browser
2. Program executed on Web server that searches through
database
3. Database typically contains URL’s to specific Web sites and
descriptions of site contents
• Info sometimes entered by administrators
• Info also gathered by programs running on Web server
Based on material  2000 Deitel & Associates, Inc.
1 # Fig. 27.38: search.pl
2 # Program to search for Web pages
3
4 use CGI qw/:standard/;
5
6 my $search = param(SEARCH);
7 my $counter = 0;
8
9 print header;
10 print "<BASEFONT FACE = \"ARIAL,SANS-SERIF\" SIZE = 3>";
11
12 open(FILE, "urls.txt") ||
13
die "The URL database could not be opened";
14
15 while(<FILE>)
16 {
17
my @data = split(/\n/);
18
19
foreach $entry (@data)
20
{
21
my ($data, $url) = split(/;/, $entry);
22
23
if ($data =~ /$search/i)
24
{
25
if ($counter == 0)
26
{
27
print "<STRONG>Search Results:<BR><BR></STRONG>";
28
}
29
30
print "<A HREF=\"http://$url/\">";
31
print "http://$url/";

2000
Deitel
&
Associates,
Inc. All rights reserved.
32
print
"</A>";
Outline
1.1 use Cgi
standard library
2.1 Open database file
3.1 Use while
structure to search
through file
3.2 split array into
hash, search for
matches to search
string
3.3 Test to see if first
result, if yes, enter
output header
3.4 Output results as
they are found
33
34
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37
38
39
40
41
42
43
44
45
46
47
48
49
print "<BR>$data<BR><BR>";
$counter++;
}
}
}
close FILE;
if ($counter == 0)
{
print "<B>Sorry, no results were found matching </B>";
print "<FONT COLOR = BLUE>$search</FONT>. ";
}
else
{
print "<STRONG>$counter matches found for </STRONG>";
print "<FONT COLOR = BLUE>$search</FONT>";
}
Outline
3.5 Increment counter
3.6 Close FILE
4.1 Test to see if no
matches found fro
search string
4.2 Set final actions
5.1 Write database file:
urls.txt
50 This site contains information about Perl and CGI;www.perl.com
51 The Deitel and Deitel Web Site;www.deitel.com
52 Purchase books on this web site;www.amazon.com
53 Perl for the Win32 platform;www.activestate.com
54 The Perl Mongers Web page;www.pm.org
55 Monthly online Perl periodical;www.perlmonth.com
 2000 Deitel & Associates, Inc. All rights reserved.
89
Script Output
Based on material  2000 Deitel & Associates, Inc.
90
Script Output
Based on material  2000 Deitel & Associates, Inc.