CS 360

1
CS 360

• Internet Programming

2
Objectives for this class period

• Web programming is important
• Administrative organization of the course
• Introduction to first two labs
• Basic Perl

3
Job Postings

• In terms of specific technologies you should be
  familiar with, you should be comfortable
  programming in Java, PHP, and/or .NET (any, but
  not necessarily all, are desirable). Excellent
  working knowledge of HTML is a must. It would
  also be helpful to have some experience with
  JavaScript, HTTP, and regular expressions.
  Familiarity with other web-related technologies
  such as Active Server Pages and J2EE is helpful.
  You should also have experience working with
  relational databases (e.g., mySQL).

4
Job Postings

• This full-time or part-time programmer would help
  develop our current web application in
  JavaScript, PHP, MySQL, Flex (a bonus), (minimum
  2 years experience in PHP). We are moving in a
  transition to AJAX and Python for portions of our
  application and knowledge in these areas is a
  bonus.

5
What is CS 360?

• It gives you the skills you need to apply for
  these jobs
• It provides you with Operating System
  Fundamentals
• File Systems
• Semaphores
• Sockets
• You should have a good architectural view of
  internet programming

6
Overview

• 15 Laboratories will keep you busy
• Due nearly every week
• Midterm and Final covering book material
• Homework
• Due each Friday
• Create a web page
• This class should be a lot of fun!

7
First Lab Due Wednesday

• Create a web page for homework assignments
• Make it passwd protected

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The first real lab is due on Friday

• Install Apache
• Write Perl code to test performance
• You will apply this to your web server in future
  labs
• This shouldnt be hard, but you need to get
  started now

9
Perl Introduction

• Uses
• Shell scripts
• CGI, web engines
• Good at
• Text processing
• Small/Medium sized projects
• Quick and dirty solutions
• Portability (to a certain degree)

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Perl Introduction

• Bad at
• Efficient large scale computation
• Neat code!

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Hello World
!/usr/bin/perl This is a comment. It goes to
the end of the line. Perl is easy. It helps to
be neat. Just like C, every statement must end
with print Hello World\n
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Perl Data Types

• Three Main Datatypes
• Scalar
• A single number, string or reference.
• sequence acgtac
• num 6
• num num 1
• List
• A collection of scalar datatypes.
• _at_insects ( hopper acgtacacactgca,
  flick acgcacacattgca, Catapillar
  acgcatattttgca)
• insectsnum ant attaccagga
• Length of an array insects
• Hash
• Pairs of scalars, accessed by keys.
• hash ( Spins gt Atlas, Sings gt
  Goldfish )
• hashSpins Globe

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Perl Context

• Operations may return diferent values, or do
  different things based on the context in which
  they are called.
• Reading from a filehandle
• one_line ltFILEHANDLEgt
• _at_whole_file ltFILEHANDLEgt
• Removing Newlines
• chomp(string)
• chomp(_at_list)

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Perl Syntax

• Basic Operators - / -- -
  /
• String concatenation newstring s . another
  string
• Numerical operations
• if(x y) Equality
• if(x lt y) Less than or Equal to
• if(x gt y) Greater than
• String operations (Based on lexial ordering)
• if (s1 eq s2) Stringwise equality
• if(s1 gt s2) Stringwise greater than
• if(s1 le s2) Stringwise less or equal

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Perl Basics if

• Selective evaluate blocks of code depending on a
  condition.
• If (string eq blah)
• print String is blah\n
• elsif (string eq spoo)
• Print String is spoo\n
• else
• Print String isnt either?\n

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Perl Basics - if

• Can also be done as a one-liner
• print String is foo\n if (string eq foo)
• Unless (Not if)
• print String is not foo\n unless (string eq
  foo)
• Unless cannot have else or else if components.

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Perl Basics for

• Practically the same as C/C/Java
• for (i 0 i lt 10 i)
• print i is . i . \n

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Perl Basics foreach

• A handy way of processing a list
• foreach grocery (_at_groceries) scan(grocery)
  
• Can use the default variable (_)
• foreach (_at_groceries) scan(_)

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Perl Default Variables

• Most basic functions will operate on the default
  variable by default.
• foreach (_at_list)
• chomp
• print
• Above chomps each element, and prints it.

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Perl Basics

• Command-line arguments
• Contained in _at_ARGV
• Strings just like C
• ARGV0 is not the program name
• Environment variables
• Contained in ENV
• print ENVPATH

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Perl Basics - Subroutines

• Identified by keyword sub
• Arguments come in _at__
• Local variables identified by keyword my

!/usr/bin/perl t1 1 t2 2 t3
testsubroutine(t1, t2) print "The answer from
testsubroutine is t3\n" sub testsubroutine
my arg1 shift _at__ my arg2
shift Since _ is default variable, we dont
have to type it return arg1 arg2
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Perl Filehandles

• An interface to an open file.
• Line read operator is angle brackets.
• open(INFILE, dna1.txt) or die cant open
  dna1.txt !
• while(ltINFILEgt) print line
  _\n
• ltSTDINgt
• ltSTDERRgt
• Opening files in other modes
• Change the filename string
• ltdna1.txt read dna1.txt
• gtdna2.txt output to dna2.txt
• gtgtdna2.txt append to dna2.txt

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Perl File Reading Writing
FILE1 ARGV0 FILE2 ARGV1 open(FILE1)
or die "Unable to open FILE1 for
reading\n" open(FILE2, "gt . FILE2) or die
"Unable to open FILE2 for writing\n" while
(ltFILE1gt) print FILE2 _ close(FILE1) cl
ose(FILE2)
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Running other programs

• Use back ticks
• people who
• Use the system command
• system(who gt who.dat)
• Using piped input
• open(PEOPLE, who )
• while(ltPEOPLEgt) print _ is
  logged on\n

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Libwww

• Dont worry about the CGI in the examples, we
  will get to it later

Create a user agent object use
LWPUserAgent ua LWPUserAgent-gtnew
ua-gtagent("MyApp/0.1 ") Create a request
my req HTTPRequest-gtnew(POST gt
'http//search.cpan.org/search')
req-gtcontent_type('application/x-www-form-urlenco
ded') req-gtcontent('querylibwww-perlmodedis
t') Pass request to the user agent and get
a response back my res ua-gtrequest(req)
Check the outcome of the response if
(res-gtis_success) print res-gtcontent
else print res-gtstatus_line, "\n"

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This is really easy

• Practice and work with examples from the web.
• Look at all of the response elements
• You will want to use this perl script to debug
  your web server.