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Server-Side Programs and Perl 5 : 

1 Server-Side Programs and Perl 5 Outline Server-Side Includes (SSI) Common Gateway Interface (CGI) 3 Introduction to Perl String Processing and Regular Expressions 4 Viewing Client/Server Environment Variables 5 Form Processing and Business Logic Verifying a Username and Password Code 7 Cookies and Perl

1 Server-Side Includes : 

2 1 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 webmasters 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 documents

1 Server-Side Includes (II) : 

3 1 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: <!-- #EXEC CGI="cgi-bin/counter.pl" --> Executes the Perl script counter.pl, located in /cgi-bin directory on server

1 Server-Side Includes (III) : 

4 1 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 ? Apache Tutorial

1 Server-Side Includes (III) : 

5 1 Server-Side Includes (III) EXEC CGI command Used to include CGI program output Example follows To see what our servers (at Dal FCS) do see examples/SSI/test1.shtml (what the client gets) examples/SSI/test1.source (code at the server)

Slide 6: 

14 Execute Perl script counter.pl using EXEC CGI statement 18 Use ECHO VAR statements to display environmental variables

Slide 7: 

Continue printing environmental variables using ECHO VAR statements

Slide 8: 

8 Script Output

Slide 9: 

5. Open counter.dat, assign to filehandle COUNTREAD 7. Increment data in COUNTREAD 8. Close COUNTREAD 6. Assign data contained in file counter.dat to variable $data 17. Use for structure to output number of page hits using number images

1 SSI (Perl preview) : 

10 1 SSI (Perl preview) 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 Returns false on error File handles do not need type ($,@,%) While file open, referenced using fileHandle Close file using the close() statement Format: close(fileHandle); Error checking: open(COUNTREAD, "counter.dat") || die "opening 'counter.dat': $!"; See die.pl and warn.pl examples

1 SSI (Perl preview) : 

11 1 SSI (Perl preview) 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

1 SSI (Perl preview II) : 

12 1 SSI (Perl preview II) 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

2 Common Gateway Interface (CGI) : 

13 2 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 Web-based 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

2 Common Gateway Interface (CGI) (II) : 

14 2 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

2 Common Gateway Interface (CGI) (III) : 

15 2 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

2 Common Gateway Interface (CGI) (IV) : 

16 2 Common Gateway Interface (CGI) (IV) Data path of a typical CGI-based application

2 CGI Binaries at FCS : 

17 2 CGI Binaries at FCS On borg Must be in ~/public_html/cgi-bin/ directory Must end with .cgi no matter what language they're in Use http://borg.cs.dal.ca We run suexec CGI programs are opened by http daemon CGI programs are run by the owner Your CGI programs have your permissions Other options: setuid, run as http (or nobody) See examples/CGI/about.pl

2 Configuring Personal Web Server (PWS) for Perl/CGI : 

18 2 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 3 in Deitel, et al. (on reserve in Killam Library)

3 Introduction to Perl : 

19 3 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

3 Introduction to Perl : 

20 3 Introduction to Perl Current version: Perl 5.8 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

3 Introduction to Perl (II) : 

21 3 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 — 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)

3 Introduction to Perl (III) : 

22 3 Introduction to Perl (III) Perl command line switches (case sensitive)

3 Introduction to Perl (IV) : 

23 3 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

Slide 24: 

1.1 Print Statement Welcome to Perl!

3 Introduction to Perl (V) : 

25 3 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

Slide 26: 

1.1 Demonstrate variable in string before initialization 1.2 Demonstrate addition involving variable using print statements 1.3 Add integer to string and print result Add integer to string and print result Using a variable before initializing:Adding uninitialized variable num to 5 yields: 5.The value of variable a is: 5Variable a after adding 5 is 10.Adding a string to an integer yields: 10Adding an integer to a string yields: 7

3 Introduction to Perl (VI) : 

27 3 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

3 Introduction to Perl (VII) : 

28 3 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)

Slide 29: 

1.1 Define array @array 2.1 Print contents of @array 2.2 Print third element of @array 3.1 Define array @array2 3.2 Explain and print contents of @array2 The array contains:Bill Bobby Sue MichelleThird element: SueThe range operator is used to store allletters 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

3 Introduction to Perl (VIII) : 

30 3 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

3 String Processing and Regular Expressions : 

31 3 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

Slide 32: 

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 Test matches Test.Testing does not match Test.

3 my and local : 

33 3 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 following program …

3 my and local (program) : 

34 3 my and local (program) $lo = 'global'; $m = 'global'; A(); sub A { local $lo = 'string'; my $m = 'string'; B(); } sub B { print "B ", ($lo eq 'string' ?'can' :'cannot'), " see the value of lo set by A.\n"; print "B ", ($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.

3 String Processing and Regular Expressions (II) : 

35 3 String Processing and Regular Expressions (II) eq operator Cannot be used to search through a series of words String binding ‘operator’ =~ Tests whether match for a string is found within a single string or series of words Example $search =~ /Test/; Searches for word test within indicated string $string =~ s/Regular/regular/g; Makes the substitution operation work on $string, instead of $_

3 String Processing and Regular Expressions (III) : 

36 3 String Processing and Regular Expressions (III) Some meta/modifying characters ^ – indicates beginning of a line $ – indicates end of a line (matches \n) \b – indicates word boundary \w – matches any alphanumeric character and underscore [a-z_A-Z0-9] Other modifying characters

Slide 37: 

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 Test was found.Test was found at the beginning of the line.Word ending in es: matches

4 Viewing Client/Server Environment Variables : 

38 4 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 (we'll see example shortly) use statement Includes predefined library packages in programs

4 Viewing Client/Server Environment Variables (II) : 

39 4 Viewing Client/Server Environment Variables (II) 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 lexographical order Assigns current key to $key and performs indicated actions

Slide 40: 

1.1 use standard CGI library 2.1 Print top of HTML Table 3.1 Use foreach function to sort through keys in %ENV hashtable 3.2 Print current keys in table 4.1 Close table

Slide 41: 

41 Script Output

4 env.cgi : 

42 4 env.cgi Source: .../examples/perl/env.pl.source Execute

4 Taint mode : 

43 4 Taint mode When in taint mode perl won't let you user input to open files, etc. Taint mode on when running as CGI or with –T switch -T must be first switch, use –Tw to get both T and w To remove taint from variables Use regular expression backreferences $file = param("filename"); # input from CGI form if ( $file !~ /^([\w.-]+)$/ ) { die "filename `$file´ has invalid characters\n"; } else { $file = $1; }

4 CGI Binaries at FCS : 

44 4 CGI Binaries at FCS On borg Must be in ~/public_html/cgi-bin/ directory Must end with .cgi no matter what language they're in Use http://borg.cs.dal.ca

5 Form Processing and Business Logic : 

45 5 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 Example

Slide 46: 

1.1 Open FORM 1.2 Define FORM attributes 1.3 Insert and define form INPUT elements 1.4 Specify correct input format

Slide 47: 

1.5 Continue inserting and defining form INPUT element 1.6 Close FORM element

Slide 48: 

48 Script Output

5 Form Processing and Business Logic (II) : 

49 5 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

Slide 50: 

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

Slide 51: 

3.3 Finish inputting if structure actions and close structure 4.1 Set actions to be performed if if structure returns a FALSE value

Slide 52: 

52 Script Output 1

Slide 53: 

53 Script Output 2

6 Verifying Username & Password : 

54 6 Verifying Username & Password Often desirable to have private Web site Developers often employ username and password authentication to implement privacy In reality we would use the server software to do this We'll see an example with perl 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)

6 Verifying Username & Password (II) : 

55 6 Verifying Username & 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 Assigns a line at a time to $_ 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

6 Verifying a Username and Password (III) : 

56 6 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

6 Verifying a Username and Password (III) : 

57 6 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! String "00" is true!

6 Verifying a Username and Password (III) : 

58 6 Verifying a Username and Password (III) sub functionName {…} Sets actions of user-defined function functionName User-defined functions accessed: &functionName — old style, not used much functionName() — preferred form, allows for extras

Slide 59: 

1.1 Print instructions 2.1 Open FORM and define ACTION attribute 3.1 Open HTML TABLE

Slide 60: 

3.2 Insert and define INPUT elements for username and password 3.3 Insert INPUT submit button 3.4 Close TABLE and FORM elements

Slide 61: 

61 Script Output

Slide 62: 

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

Slide 63: 

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

Slide 64: 

6.1 Define wrongpassword function 6.2 Print ‘invalid password’ message 7.1 Define accessdenied function 7.2 Print ‘access denied’ message

Slide 65: 

Data.txt 1.1 Input username and password combinations using format: username,password/n

6 Verifying a Username and Password (IV) : 

66 6 Verifying a Username and Password (IV) See example Fig_27_25.pl

Slide 67: 

67 Script Output

6.5 Sending E-Mail From a Web Browser : 

68 6.5 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

6.5 Sending E-Mail From a Web Browser : 

69 6.5 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

Slide 70: 

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

Slide 71: 

2.3 Insert and define remaining INPUT elements for email fields 2.4 Insert and define TEXTAREA for body of email message

Slide 72: 

1.1 Close TABLE and FORM tags Script Output

Slide 73: 

1.1 use SMTP 1.2 use CGI standard library 2.1 Set local variable values to user form inputs 3.1 print ‘request processed’ message 4.1 Connect to SMTP server 4.2 Form email message using data(), datasend() and dataend() functions 4.3 quit smtp server

Slide 74: 

74 Script Output

7 Cookies : 

75 7 Cookies What? Client-side storage for server-side use Why? To save state information How? When server sends document is can also send a cookie When client requests document it can also send back cookie with request

7 Cookies : 

76 7 Cookies Some Details Server sends ‘Set-Cookie:’ header NAME = VALUE is required Parameters separated by semicolons (;) Optional parameters Expires= When the cookie ceases to be (crumbles) If not set then expiry is end of browser process Domain= Site to send cookie back to Path= What file (directory) it applies to Secure= Do not send with unsecured protocol

7 Cookies : 

77 7 Cookies Some More Details Multiple set-cookie headers allowed Cookies can overwrite each other Expires times in the past are used to delete cookies Limits: 300 cookies 4 Kb per cookie 20 cookies per server or domain

7 Cookies : 

78 7 Cookies Examples from the draft specification

7 Cookies : 

79 7 Cookies

7 Cookies and Perl (II) : 

80 7 Cookies and Perl (II) To set a cookie using plain 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

7 Cookies and Perl (III) : 

81 7 Cookies and Perl (III) Internet Explorer stores cookies Text file added to Temporary Internet Files directory Filename: Cookie:administrator@ip.number

Slide 82: 

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

Slide 83: 

83 Script Output

Slide 85: 

85 Script Output

7 Cookies and Perl (IV) : 

86 7 Cookies and Perl (IV) Cookies are read from client machine using Perl Subroutine 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

Slide 87: 

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

Slide 88: 

4.3 Split cookie entry names and values 4.4 Return information for output

Slide 89: 

89 Script Output

7 Cookies and CGI.pm : 

90 7 Cookies and CGI.pm use CGI qw(:standard); my $cookie = cookie(-name=>'regular', -value=>'chip'); print header(-cookie=>$cookie); --------------------------------------- Set-cookie: regular=chip Content-type: text/html Examples