Week Four Agenda

Week Four Agenda•Announcements•Link of the week•Review week three lab assignment•This week’s expected outcomes•Next lab assignment•Break-out problems•Upcoming deadlines•Lab assistance, questions and answers

AnnouncementsScript Comments

Scripts should contain the following comments:

Editing Author:

Script Functionality:

Lab Assignment:

Due Date:

Link of the Week

Object Code • https://freedom-to-tinker.com/blog/felten/source-code

-and-object-code

• What is object code?• http://www.linfo.org/object_code.html• Object File Format

https://freedom-to-tinker.com/blog/felten/source-code-and-object-code

https://freedom-to-tinker.com/blog/felten/source-code-and-object-code

http://www.linfo.org/object_code.html

Link of the Week

SourceFile

SourceFile

SourceFile

SourceFile

SourceFile

Object File

Object File

ObjectFile

Object File

ObjectFile

LinkerRuntimeLibrary

ExecutableProgram

Source/Object/Executable Drawing

Link of the Week

Review Week Three Lab Assignment

Textual (command-line) and visual interfaces (graphical) are two common interfaces used to support engineering tasks on systems. Both utilize Netflows data as the main resource.

Netflows are network-based logs that are collected from a network ‘s router. They provide records of the flows that occur on the network. A Netflow record contains a wide variety of useful information about the traffic in a given flow.


SolarWinds NetFlow Traffic Analyzer (NTA) analyzes Cisco NetFlow, Juniper J-Flow, IPFIX, sFlow, & Huawei NetStream™ data to deliver a complete picture of network traffic, identifying who and what are consuming your bandwidth.


What is a filter?A UNIX filter command performs an operation or manipulation of the input text from a file. Standard in and out are typically used during this operation.

UNIX Command Line Filters

awk, cat, cut, expand, compress, fold, grep, head, nl, perl, pr, sed, sh, sort, split, strings, tail, tac, tee, tr, uniq, and wc

Review Week Three Lab AssignmentFile System Filters

cat, cd, chmod, chown, chgrp, cksum, cmp, cp, dd, du, df, fsck, fuser, ln, ls, lsattr, lsof, mkdir, mount, mv, pwd, rm, rmdir, split, touch, umask

Processes Filters

at, chroot, cron, exit, kill, killall, nice, pgrep, pidof, pkill, ps, pstree, sleep, time, top, and wait


Test CommandA common way to set up a condition for the if command is with the test command.

test condition or [ condition ]

The test command evaluates the condition and returns 0 or 1, depending on the results of the test.The brackets work exactly like the test condition. The open bracket is a link to test.


Constructing Conditions-s file -r file -w file -S file-x file -f file -d file

Examples: if [ ! –f /etc/.fsckask ]If the plain file /etc/.fsckask does not exist

If [ -d /etc/rc0.d ]If there is a directory named /etc/rc0.d


Perl is a simple language that compiles and executes like a shell or batch type file.

Perl doesn’t impose special growth limitations on an array or data strings

Perl is a composite of C, AWK, and Basic.

Perl was originally developed to manipulate text information.

Review Week Three Lab Assignment• Perl’s capabilities range from

- System administration- Web development- Network programming- GUI development

• Perl’s major features are- Procedural Programming makes use of simple

sequential steps, routines, subroutines, and methods.

- Object Oriented Programming (OOP) makes use of “objects”. The key elements of are inheritance, modularity, polymorphism, and encapsulation.

Review Week Three Lab AssignmentPerl and Shell SimilaritiesPerl scalar@ARGV ~ Shell $#Perl $ARGV[0] ~ Shell $1Perl $ARGV[1] ~ Shell $2Perl unless(scalar(@ARGV)==2) ~ Shell if [ $# != 2]All Perl statements are terminated with a “;”Perl exit 0 is returned if execution was

successful.Perl exit 1 is returned if execution fails.

Review Week Three Lab AssignmentPerl syntax$? - this variable contains the return value # - precedes a comment statement in Perl\n - new line syntax“ …” $strexp = “This text is considered as a

string”;‘ …’ $charexp = ‘a’;` …` $cmdexp = `ls –l`;@ARGV – array containing command line

arguments$_ - default implied scalar


There are two types of relational operators. One class operates on numeric values, the other on string values.

Relational operators

Numeric String Meaning

> gt Greater than

>= ge Greater than or equal

< lt Less than

<= le Less than or equal


Equality Operators

Numeric String Meaning

== eq Equal to

!= ne Not equal to

cmp Comparison, sign results

-1 if the left operand is less

0 If both operands equal

1 If the left operand is greater


Commands

cal –y (display a calendar for the year)

cal –j 2010 (display Julian dates)

cal –m 2010 (display Monday first day)

cal –s 2010 (display Sunday first day)

cal 9 2010 (display September 2010 month)

Week Four Expected OutcomesLearning Outcomes• Write Perl scripts, including variables, control

flow, and regular expression syntax

Next Lab Assignment

• Perl is designed to

- Process text data

- Perform pattern matching

- Utilize string handling tasks• Perl is available on many platforms

- UNIX

- Linux

- HP-UX

Next Lab Assignment

Perl utilizes two types of categories Singular variables that represent a

single- value. The variable prefix symbol for a scalar is the $.

Plural variables are ones that contain multiple-values. Arrays and hashes are two multi-valued variables. The variable prefix symbol for an array and hash are @ and

%, respectively.

Next Lab Assignment

Perl data types $answer = 42; (an integer) $pi = 3.14159265; (a “real” number)

$animal = “horse”; (string) $statement = “I exercise my $animal”;

(string with interpolation) $amount = ‘It cost me $5.00’;

(string without interpolation)

$cwd = `pwd`; (string output from a command)

Next Lab AssignmentInitialize Perl array:

Definition: An array is an ordered list of scalars, accessed by the scalar’s position in the list.

@garage = (“car”, “mower”, “broom”);

@persons = (“Will”, “Karim”, “Asma”, “Jay”);

$count = @persons;

Extecute Perl script:

./week_four.pl

Next Lab AssignmentOpen Statement

The open function can be used to create file handles for different purposes (input, output, and piping), you need to be able to specify which behavior you want.

Next Lab Assignmentopen functions

open(file_handler, “file_name”)

open(file_handler, “<file_name”)

open (file_handler, “>file_name”)

open (file_handler, “>>file_name”)

See page 21 in your Perl text.

Next Lab AssignmentFilehandle is utilized for both input and output files.

Most file names are cryptic and are meaningless to programmers. The purpose of a filehandle is to help the programmer remember a simple file name throughout a program.

A filehandle is a name given for a file, device, socket, or pipe.

Filehandle command line format:open(filehandle, file name, permissions,

chmod);

Example: open($FH,$file_name);

Next Lab AssignmentIf you want to read text from a file line-by-line, then

you want to use the following syntax: my @lines = <FILE>;

The <FILE> operator - where FILE is a previously opened filehandle - returns all the unread lines of the text file in list context or a single line in scalar context. Hence, if you had a particularly large file and you wanted to conserve memory you could process it line by line:

while (<FILE>) { print $_;

}

Next Lab AssignmentPerl Formats

if ( … ){

…}

while ( … ){

…}


for ( initialize variable, test variable, increment variable){

…}


if ($append) { open(MYOUTFILE, ">filename.out");

#open for write, overwrite }else { open(MYOUTFILE, ">> filename.out");

#open for write, append }

Next Lab AssignmentWhat is List Processing?

@math_array = (6 - 4, 4 * 4, 8 / 2, 9 - 8);while ( … ) {

…}

Next Lab AssignmentWhat is a for loop?

for (counter = 0; counter < 10; counter++) {

…}

Three expressions are contained in a for loop: 1. Set initial state of the loop variable 2. Condition test the loop variable 3. Modify the state of the loop variable

Next Lab AssignmentForeach Statement Format

foreach VAR (List){

…}

Read a list of valuesExecute Perl script:

./read_list.pl

Next Lab AssignmentForeach Statement Format@myNames = ('Larry', 'Curly', 'Moe');foreach (@myNames)

{print $_;

}

Sum the elements in an array Execute Perl script:

./sum_list.pl

Next Lab AssignmentDisplay the content of an array

Execute Perl script:./array_display.pl

Sort the elements in an array

Execute Perl script:./array_sort.pl

Next Lab AssignmentRegular ExpressionsDefinition: Regular expression provides a concise and

flexible means for "matching" (specifying and recognizing) strings of text, such as particular characters, words, or patterns of characters. Abbreviations for "regular expression" include "regex" and "regexp". The concept of regular expressions was first popularized by utilities provided by Unix distributions, in particular the editor “ed” and the command/filter grep.

Example: if ( /UNIX V5/ ) {print “UNIX V5 found on system. \n”;}

Next Lab AssignmentRegular Expressions

Substitution operator: s/original value/new value/Character class: Matches a single character that is contained within the brackets [ a-zA-Z0-9_ ] Special or meta characters are used to denote actions or delimit groups:

+ means “one or more of whatever was before the + symbol”

. Matches any single character (i.e., x.z) ^ Matches the starting position within the string $ Matches the ending position of the string or

the position just before a string-ending newline

Next lab assignmentPerl Program Statement

#!/usr/bin/perl #!/usr/bin/perl -w

Print continuation statementprint "error: incorrect number of arguments", "\n", "usage: intlist a b (where a < b)", "\n";

Execute Perl scripts:./linenum.pl and ./intlist.pl

Break-out problems• $strexp = “This text is considered as a string”;• $intexp = 10;• $floatptexp = 2.54;• $charexp = ‘a’;• $cmdexp = `ls –l`;• $argexp = (“two”, “four”, “six”);• @array_exp = (“Jackie”, “Vicki”, “Alex”);• $array [0] = “new value”;• $a = $b + 5;• $container = @container;• ($map{blue}, $map{orange}, $map{jade}) = (0xff0000, 0x00ff00,

0x0000ff0);

Next Lab Assignment

Programming Perl text book reading

Chapter One

Chapter Two

Chapter Three

Upcoming deadlines

Lab Assignment 3-1 is due on September 27, 2012.

Lab Assignment 4-1 is due on October 4, 2012.

Lab Assignment 7-1, Midterm exam administered from October 15 through 20.

Midterm outline to be posted on the Bulletin Board by September 30, 2012.

Questions and answers

• Questions• Comments• Concerns

• After class, I will help students with their scripts.

Documents

Week Four Agenda