Modules Intermediate Perl Programming Part 2 1 of 42 What is a - - PDF document

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Modules Intermediate Perl Programming Part 2 1 of 42 What is a - - PDF document

Feb 04, 2024 41 likes •255 views

Modules Intermediate Perl Programming Part 2 1 of 42 What is a module? MyModule Intermediate Perl Programming Part 2 2 of 42 What is a module? $MyModule::x @MyModule::a MyModule::do_this() MyModule::do_that() MyModule

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1 of 42 Intermediate Perl Programming – Part 2

Modules

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What is a module? MyModule

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SLIDE 2

3 of 42 Intermediate Perl Programming – Part 2

What is a module? MyModule

MyModule::do_this() MyModule::do_that() $MyModule::x @MyModule::a

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What is a module? main

main::do_this() main::do_that() $main::x @main::a

package main; # Package vars use vars qw($x @a); # Subroutines sub do_this { ... } sub do_that { ... }

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5 of 42 Intermediate Perl Programming – Part 2

What’s the point? Protect one part of your program from another Make your program easier to understand Code reuse (laziness is a virtue!)

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Objects and classes

A thumbnail sketch

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SLIDE 4

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Class A module you can use to create objects use Some::Module; my $object = Some::Module->new; Just tell it to create one

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Object Another black box Has properties you can tell it to get or set Has behavior – if you tell it do something, it reacts in a certain way use Some::Module; my $object = Some::Module->new; print $object->name; $object->jump('up');

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9 of 42 Intermediate Perl Programming – Part 2

HTTP, CGI, and DBI

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User’s computer

Web server HTTP

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SLIDE 6

11 of 42 Intermediate Perl Programming – Part 2

Web server

Apache

HTTP

search.pl checkout.pl

CGI

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Web server

Apache

HTTP

search.pl checkout.pl

CGI

Database

DBI

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SLIDE 7

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HTTP

2 min. overview

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HTTP request/response exchange

GET /cgi-bin/hello.pl HTTP/1.0 User-Agent: Safari/1.1

Web server User’s computer

HTTP/1.0 200 OK Date: Tue, 17 Oct 2006 12:56:29 GMT Server: Apache/1.3.37 Last-Modified: Fri, 13 Oct 2006 19:42:06 GMT Content-Type: text/plain Content-Length: 14 Hello, world!

Request Response

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CGI

Common Gateway Interface

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CGI exchange

GET /cgi-bin/hello.pl HTTP/1.0 User-Agent: Safari/1.1

Request

HTTP/1.0 200 OK Date: Tue, 17 Oct 2006 12:56:29 GMT Server: Apache/1.3.37 Last-Modified: Fri, 13 Oct 2006 19:42:06 GMT Content-Type: text/plain Content-Length: 14 Hello, world!

Response

Apache search.pl

Environment variables (Standard input) Standard output

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SLIDE 9

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hello.html – the user interface

Name (optional):

Yolanda

Greet me

http://eowyn.simmons.edu/ceperl/hello.html

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hello.pl – the CGI program

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

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SLIDE 10

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • The program relies upon the CGI module. This statement

checks to make sure it’s available and – if it is – gives it an

  • pportunity to perform any initialization it requires.

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • We use a generic greeting by default.
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SLIDE 11

21 of 42 Intermediate Perl Programming – Part 2

hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • Ask the CGI module to create a new object containing the data

that the web server program has passed to us.

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • Look for a “name” parameter. This is the text that the user typed

into the HTML input field named “name” .

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SLIDE 12

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • Don’t assume that there was such a field! The ”user” could be a

malicious program in disguise.

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • Check to see if the user left the ”name” field blank.
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SLIDE 13

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • OK, use the name they supplied.

Normally, we would be careful to check to make sure the value supplied wasn’t malformed, but we don’t bother here because we’re only going to send the name back to the user.

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • The content that we’re generating on the web server program’s

behalf is plain text.

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SLIDE 14

27 of 42 Intermediate Perl Programming – Part 2

hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • A blank line separates the HTTP header from the content.

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hello.pl

use CGI; my $user_name = 'whoever you are'; my $query = CGI->new; my $name_supplied = $query->param('name'); if (defined $name_supplied and $name_supplied ne '') { $user_name = $name_supplied; } print "Content-Type: text/plain\n"; print "\n"; print "Hello, $user_name!\n";

  • Send our greeting. The web server program will take care of all
  • ther nitpicky details.
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29 of 42 Intermediate Perl Programming – Part 2

hello.pl – the result

Hello, Yolanda!

30 of 42 Intermediate Perl Programming – Part 2

hello.pl – try it out http://eowyn.simmons.edu/ceperl/cgi-bin/hello.pl http://eowyn.simmons.edu/ceperl/cgi-bin/hello.pl?name=Yolanda http://eowyn.simmons.edu/ceperl/cgi-bin/badger/hello.pl http://eowyn.simmons.edu/ceperl/cgi-bin/loris/hello.pl — etc.

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31 of 42 Intermediate Perl Programming – Part 2

KidCat

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Databases

SQL and RDBMSes in a nutshell

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33 of 42 Intermediate Perl Programming – Part 2

Tables

isbn year publisher place edition author title id Works renewals due checked_out item_id user_id UserItems barcode call_number library_id part work_id id Items name id Libraries barcode email status category lastname firstname id Users

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Columns and rows

Happenstantz hellion604@yahoo.com 6 A Wilhelmina 1085 S T 3928 xaxelrod@goatisland.edu A Xerxes Axelrod 1 A 5019 S Ipswich Yolanda 3 yoyo@mama.org barcode email status category lastname firstname id

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35 of 42 Intermediate Perl Programming – Part 2

DBI

Perl database interface

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The DBI mantra

Connect Prepare Execute Fetch Error checking!

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37 of 42 Intermediate Perl Programming – Part 2

Connect

$dbh = DBI->connect( $data_source, $user, $password );

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Prepare

$dbh = DBI->connect( $data_source, $user, $password ); $sth = $dbh->prepare($query);

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39 of 42 Intermediate Perl Programming – Part 2

Execute

$dbh = DBI->connect( $data_source, $user, $password ); $sth = $dbh->prepare($query); $sth->execute;

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Fetch

$dbh = DBI->connect( $data_source, $user, $password ); $sth = $dbh->prepare($query); $sth->execute; while (@row = $sth->fetchrow_array) { ... }

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41 of 42 Intermediate Perl Programming – Part 2

Error checking

$dbh = DBI->connect( $data_source, $user, $password ) or die; $sth = $dbh->prepare($query)

  • r die;

$sth->execute or die; while (@row = $sth->fetchrow_array) { ... } die if $DBI::err;

42 of 42 Intermediate Perl Programming – Part 2

Error checking simplified

$dbh = DBI->connect( $data_source, $user, $password, { 'RaiseError' => 1 } ); $sth = $dbh->prepare($query); $sth->execute; while (@row = $sth->fetchrow_array) { ... }