Download Lec-1-perl

CS 360
Internet Programming
Objectives for this class period
Web programming is important
 Administrative organization of the course
 Introduction to first two labs
 Basic Perl

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).
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.
What is CS 360?


It gives you the skills you need to apply for
these jobs
It provides you with Operating System
Fundamentals

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File Systems
Semaphores
Sockets
You should have a good architectural view of
internet programming
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

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This class should be a lot of fun!
First Lab Due Wednesday
Create a web page for homework
assignments
 Make it passwd protected

The first real lab is due on
Friday
Install Apache
 Write Perl code to test performance
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You will apply this to your web server in
future labs
This shouldn’t be hard, but you need to
get started now
Perl Introduction
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Uses
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Shell scripts
CGI, web engines
Good at
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Text processing
Small/Medium sized projects
Quick and dirty solutions
Portability (to a certain degree)
Perl Introduction

Bad at
Efficient large scale computation
 Neat code!

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”;
Perl Data Types

Three Main Datatypes
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Scalar
•
•
•
•
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A single number, string or reference.
$sequence = “acgtac”;
$num = 6;
$num = $num + 1;
List
• A collection of scalar datatypes.
• @insects = ( “hopper acgtacacactgca”,
“flick acgcacacattgca”, “Catapillar acgcatattttgca”);
• $insects[$num] = “ant attaccagga”;
• Length of an array $#insects”

Hash
• Pairs of scalars, accessed by keys.
• %hash = ( “Spins” => “Atlas”, “Sings” => “Goldfish” );
• $hash{“Spins”} = “Globe”;
Perl Context
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Operations may return diferent values, or do different
things based on the context in which they are called.
Reading from a filehandle
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$one_line = <FILEHANDLE>;
@whole_file = <FILEHANDLE>;
Removing Newlines
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chomp($string);
chomp(@list);
Perl Syntax
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Basic Operators: + - * / ++ -- *= += -= /=
String concatenation: $newstring = $s . “another string”;
Numerical operations
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if($x == $y)
if($x <= $y)
if($x > $y)
Equality
Less than or Equal to
Greater than
String operations (Based on lexial ordering)
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if ($s1 eq $s2)
if($s1 gt $s2)
if($s1 le $s2)
Stringwise equality
Stringwise greater than
Stringwise less or equal
Perl Basics – ‘if’

Selective evaluate blocks of code depending on a condition.
If ($string eq “blah”)
{
print “String is blah\n”;
}
elsif ($string eq “spoo”)
{
Print “String is spoo\n”;
}
else
{
Print “String isnt either?\n”;
}
Perl Basics - ‘if’

Can also be done as a ‘one-liner’
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print “String is foo\n” if ($string eq “foo”);
Unless (Not if)
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print “String is not foo\n” unless ($string eq “foo);
Unless cannot have else or else if components.
Perl Basics – ‘for’
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Practically the same as C/C++/Java
for ($i = 0; $i < 10; $i++)
{
print “i is “ . $i . “\n”;
}
Perl Basics – ‘foreach’
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A handy way of processing a list
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foreach $grocery (@groceries)
{
scan($grocery);
}
Can use the default variable ($_)
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foreach (@groceries)
{
scan($_);
}
Perl Default Variables

Most basic functions will operate on the default
variable by default.
foreach (@list)
{
chomp;
print;
}

Above chomps each element, and prints it.
Perl Basics

Command-line arguments
Contained in @ARGV
 Strings just like C
 $ARGV[0] is not the program name
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Environment variables
Contained in %ENV
 print $ENV{“PATH”};
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Perl Basics - Subroutines
Identified by keyword “sub”
 Arguments come in @_
 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 @_;
my $arg2 = shift;
return $arg1 + $arg2;
}
#Since _ is default variable, we don’t have to type it
Perl Filehandles
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An interface to an open file.
Line read operator is angle brackets.
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open(INFILE, “dna1.txt”) or die “cant open dna1.txt: $!”;
while(<INFILE>)
{
print “line $_\n”;
<STDIN>
<STDERR>
Opening files in other modes
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Change the filename string
“<dna1.txt”
read dna1.txt
“>dna2.txt”
output to dna2.txt
“>>dna2.txt”
append to dna2.txt
}
Perl File Reading & Writing
$FILE1 = $ARGV[0];
$FILE2 = $ARGV[1];
open(FILE1) or die "Unable to open $FILE1 for reading\n";
open(FILE2, ">” . $FILE2) or die "Unable to open $FILE2 for writing\n";
while (<FILE1>)
{
print FILE2 $_;
}
close(FILE1);
close(FILE2);
Running other programs
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Use back ticks
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Use the system command
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$people = `who`;
system(“who > who.dat”);
Using piped input
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open(PEOPLE, “who |”);
while(<PEOPLE>)
{
print “$_ is logged on\n”;
}
Libwww

Don’t worry about the CGI in the examples, we
will get to it later
# Create a user agent object
use LWP::UserAgent;
$ua = LWP::UserAgent->new;
$ua->agent("MyApp/0.1 ");
# Create a request
my $req = HTTP::Request->new(POST => 'http://search.cpan.org/search');
$req->content_type('application/x-www-form-urlencoded');
$req->content('query=libwww-perl&mode=dist');
# Pass request to the user agent and get a response back
my $res = $ua->request($req);
# Check the outcome of the response
if ($res->is_success) {
print $res->content;
}
else {
print $res->status_line, "\n";
}
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.
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