2. Intro to Perl

8/8/2019 2. Intro to Perl

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Intro to Perl 1-1

Session No.2

Introduction to Perl

Deepak Chopade


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Intro to Perl 1-2

Course Objectives

To introduce Perl Scripting Language

To introduce the concept of regular expressions andpattern matching

To introduce various file operations in Perl To introduce the Database programming using Perl

To introduce the basics of Web Programming usingPerl


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Intro to Perl 1-3

What is PERL and where PERL is beingused?

PERL is scripting language

PERL is mostly used for extracting information from text files andgenerating various reports based on that

PERL is also used for developing web applications using CGI standards

It is also used for developing scripts of automated testing, systemadministration etc.

It is one of the most popular scripting language

Many projects in Infy uses Perl Scripting


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Intro to Perl 1-4

Course Pre-Requisites

The participants should have the basic knowledge ofprogramming

The participants should have knowledge of SQL


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Intro to Perl 1-5

Expectations

At the end of this course, the participants areexpected to be proficient in the following

Writing scripts using Perl

Writing simple Database related utilities in Perl


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Intro to Perl 1-6

Day 1 Introduction to Perl Scalar Variables I/O Functions Operators String and formatting strings Selectional, iterational and miscellaneous control statements

Arrays and various operations on arrays

Day 2 Hashes and various operations on hashes Regular Expressions Meta characters Character classes

Pattern matching Subroutines Command line arguments

Day Wise Session Plan (1/2)


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Intro to Perl 1-7

Day 3 File Input/Output

Various file opening modes

Database Programming using DBI & DBD

Introduction to CGI Programming using Perl

Day Wise Session Plan (2/2)


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Intro to Perl 1-9

Session Plan Day 1

Introduction to Perl

Scalar Variables

I/O Functions

Operators

String and formatting strings

Selectional, iterational and miscellaneous control

statements

Arrays and various operations on arrays


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Intro to Perl 1-10

Perl Scripting


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Intro to Perl 1-11

PERL Practical Extraction and Report Language Developed by Larry Wall in 1987

Originally designed for reading text files and preparing reports based on that

information

Combines features of C ,sed, awk and sh Gives unlimited data size

Recursion of unlimited depth

Sophisticated pattern matching techniques

Used for web programming

Widely used for system administration

Wide range of third party modules

PERL - Introduction


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Intro to Perl 1-13

PERL - Variables

Scalar Variables Simple variables containing an element, either a number or a string

Defined by $ symbol

Array List of scalar variables Defined by @ symbol

Hashes Similar to arrays

Each item is identified by a key value Defined by % symbol


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Intro to Perl 1-14

PERL Scalar Variables Defined by $ Symbol

Stores either a number or a String No declaration required, creation is done when a variable is referred first in the

program,known as auto vivification

Strings and Numbers are interchangeable

Variable names are case sensitive

Variable name can have alphabets, numbers and underscore (_)

Should not start with a number Variables starting with _ is special

$Number = 48091 #Integer type

$Name = John David #String type

$Salary = 48091.50 #Decimal type

$Message = Do you like \PERL\ Script? #String type

$Number=4809 is valid


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Intro to Perl 1-15

PERL First Perl Script

#File Name : Address.pl#Description : Script to display the address

#Author : Ajeesh G.P.

#Date : 12-Feb-2007

#Version : 1.0

# Information about Perl interpreter

# !c:\per\bin\perl

#Statements to display the Address

print John Dave\n;

print 937/s Hebbal II Stage\n;

print Mysore 18\t;

print Mobile: 9886045606\n;

#End of Address.pl


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Intro to Perl 1-16

PERL - Lists

Collection of scalar data, Arrays and Hashes Represents a logical group of items Scalar data inside ( and ) separated using , represents a list A set of operators works on list called as list operator

E.g. print print (1,2,3) displays 123

E.g.

4809

John

Dave

34000.50

($no, $name, $sal) = (4809, John Dave, 34000.50);

print $no;

print \n;

print $name;

print \n

print $sal


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Intro to Perl 1-17

#Generating a random letter using List

$RandomNumber = (51..150)[rand(100)];

print $RandomNumber

PERL Accessing List element usingIndex

John

43002

# Accessing the second element from list

$Name = (43002,John,34400.50)[1];

#Display the accessed element

print $Name

# Assigning one list to Other

($Number,$Name)=(43002,John);

($EmpNumber,$EmpName) = ($Number, $Name)

print $EmpNumber

print $EmpName

RandomNumber

between 51

and 150

John


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Intro to Perl 1-19

PERL print

# Usage in printing a number & string

#Using temporary concatenation operator .

#Output to STDERR

What is the output of the following script?

4089

John

4089John

3400.5

%.2f3400.5

Outputs to

STDERR

$Number = 4089;

$Name = John;

print $Number;

print $Name;

print $Number.$Name;

print STDERR Warning: Unable to close print.pl;

$Sal=3400.50;

print $Sal;

print %0.2f,$Sal;


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Intro to Perl 1-20

$Name=John Dave;

$No=4809;

$Sal=3400.50;

printf(\nName:%s\nNo:%d\nSal:%.2f,$Name,$No,$Sal);

$Number = 43002;

$Salary = 34000.50;

printf (Salary of %d is.2f,$Number,$Salary);

PERL printf Salary of43002 is

34000.50

$Number = 43002;

$Salary = 34000.50;

$Out=sprintf (Salary of %d is %.2f,$Number,$Salary);

print $Out;

# Display the Number and Salary using printf

#Display Name and Number

#Above script can be re written using sprintf and print

Salary of 43002 is34000.50

Name :John Dave

No:4809

Sal:3400.50


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Intro to Perl 1-21

PERL warn

What happens if warn.pl is executed in the below form? perl warn.pl > output.txt

#Filename : warn.pl

# Declare & initialize variables

$ EmpSal=34500.50;

$ EmpName=John Dave;

if($EmpSal != 0) {

#Outputs to standard output stream

printf(%d %s,$EmpSal,$EmpName);

}else {

#Outputs to Standard Error Stream

warn Salary not calculated;

warn Write to file failed;

}

34500.50 JohnDave


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Intro to Perl 1-22

PERL - Operators

Assignment Operator

Auto increment and decrement operators

Additive operators

Multiplicative operators Exponentiation Operator

Relational Operators

Logical Operators

Range Operator Binding Operator

Arrow operator

File I/O Operator


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Intro to Perl 1-23

PERL Operators contd Assignment Operator (=)

Simple assignment

Compound assignment

Auto increment and decrement operator (++, --)

Additive Operator (+, -, .) Addition & Subtraction operator

Concatenation Operator (.)

6

6

Shivkumar

$Number1 = 5;

$Number2=$Number1;

$Number3=$Number2=$Number1;

$Number=5;

print ++$Number;

print $Number++;

$FirstName=Shiv; $LastName = Kumar;

$Name = $FirstName.$LastName;

print $Name;

$Result = $No1 + $No2 -20;


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Intro to Perl 1-24

PERL Operators contd.

Multiplicative Operators Multiplication & Division

- Repetition Operator (x)

- Exponential Operator

%of

marks =

60

64

$x=4;

$y=3;

print $x ** $y;

print Hello PERL x 10;

$Mark = 30;

$Percentage=30/50*100;

print % of marks=$Percentage;

Hello PERL will be

printed 10 times


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Intro to Perl 1-25

PERL operators contd

Relational Operators Operating on Numeric data=, ==, !=,

- Operating on String data

lt less than E.g. ($Myname lt $YourName)

gt greater thanle less than or equal toge greater than or equal toeq equal tone not equal tocmp compare (returns -1, 0 , 1)

- Logical Operator

AND - && or andOR - || or orNOT - not


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Intro to Perl 1-27

PERL Standard Input

Input operator or

Read input from the user including \n from the user

chomp operator can be used for removing the \n character

By default input is stored in a default variable $_

#Read the Employee Number from the user

print Enter the Number : ;

$EmpNumber = ;

print \nEnter the Name: ;

$EmpName = ;

print \nNo : $EmpNumber \nName:$EmpName;


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Intro to Perl 1-28

PERL Standard Input contd

chomp Usually used to discard the \n character at the end of input string

20

Ajeesh

$No=;

$Name=;

print $No;

print $Name;

chomp $No;

chomp $Name;print $No;

print $Name;

20Ajeesh


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Intro to Perl 1-29

PERL - Strings

Sequence of characters, each character is an 8 bit value

Single quoted string

Escape sequence except \\ & \ are not interpreted so

Double quoted string

All escape sequences are interpreted so

No 37\nII Cross

Sheshan's

No 37

II Cross

$HouseNo = No 37\nII Cross;

$Street = Sheshan\s;

print $HouseNo;

print \n;

print $Street;

$HouseNo = "No 37\nII Cross";$Street = "Sheshans\'";

print $HouseNo;

print "\n";

print $Street;

Sheshans


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Intro to Perl 1-31

PERL String Functions

Converting to lower case using lc STRING

Converting to upper case using uc STRING

Converting initial case to lower using lcfirst STRING

Converting initial case to upper using ucfirst STRING

notepad.exe

NOTEPAD.EXE

notePad.EXE

NotePad.EXE

$FileName= "NotePad.EXE";

$FileName=lc $FileName;

print $FileName;


$FileName=uc $FileName;

print $FileName;


$FileName=lcfirst $FileName;

print $FileName;


$FileName=ucfirst $FileName;

print $FileName;


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Intro to Perl 1-32

PERL String Functions contd

Getting string length using length (STRING) Returns the length of the string

If STRING is omitted, it returns the length of the string stored in $_

Searching string using index (STRING,

SUBSTRING, [POSITION]) returns the index of the first occurrence of the SUBSTRING in STRING on orafter POSITION

If POSITION is ignored, it starts searching from the first location

returns -1 if not found

rindexcan be used to find the index of the last occurrence of the SUBSTRING inSTRING on or before POSITION

9

$FileNameDOS="MyApp.Exe";

$Length=length ($FileNameDOS);

print $Length;


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Intro to Perl 1-33


Using index

Using rindex

4

15

15

4

$Domain="www.ad.infosys.ad.com";

$Result=index($Domain,"ad");

print $Result;

print "\n";

$Result=index($Domain,"ad",13);

print $Result;

$Domain="www.ad.infosys.ad.com";

$Result=rindex($Domain,"ad");

print $Result;

print "\n";

$Result=rindex($Domain,"ad",13);

print $Result;


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Intro to Perl 1-34


Extracting/Replacing substring using

substr STRING,OFFSET,[LENGTH],REPLACEMENT

Extracts and returns the substring from OFFSET to LENGTH+OFFSET

If LENGTH is omitted, extraction starts from OFFSET to end of STRING

If LENGTH is negative, extraction omits that much number of characters from theend

If OFFSET is negative extraction starts from end of the string and moves backwards

If REPLACEMENT is specified, extracted substring will be replaced byREPLACEMENT


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Intro to Perl 1-35

PERL String Function contd

Extracting substring:

Extracting and replacing:

Reversing the String:

http

$Source="http://www.infosys.com:8080/index.html";

$Protocol=substr($Source,0,4);

print $Protocol;

$Source="http://www.infosys.com";

substr($Source,0,4,"https");

print $Source;

$Source="www.infosys.com";

$Image= reverse($Source);

print $Image;

moc.sysofni.www

https://www.infosys.com


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Intro to Perl 1-36

PERL Control Structures

Branching Statements if

if else

if elsif

Looping Statements while / until do while/ until

for

foreach

Miscellaneous Control Statements last, next, redo Expression modifiers

exit, die


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Intro to Perl 1-37

PERL Control Structures contd if statement

if ( condition ) {#True Block

} If - else statement

if( condition ) {#True Block

}else {#False Block

} if elsif statement

If( condition1) {

#T

rue block for Condition1}elsif(condition2) {#True block for Condition2

}else {#False block

}


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Intro to Perl 1-38

PERL Control Structures contd

$FileSize=;

if($FileSize==-1) {

print "File Not Found!\n";

}elsif($FileSize==0) {

print "File Empty!\n";

}else {

print "Size of the file is

$FileSize";}


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Intro to Perl 1-39


while loopwhile (condition) {

#while block statements

}

Control comes out of the loop when the condition isFALSE

until loop

until (condition) {#until block statements

}

Control comes out of the loop when the condition is TRUE


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Intro to Perl 1-40


What is the output of the following code?

What is the output of the following code?

Prints 10 9 8 7 6

Prints 210

$Loop=10;

until($Loop


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Intro to Perl 1-41


do while loopdo{

#while block statements

}while (condition)

Control comes out of the loop when the condition isFALSE

do until loop

do { #until block statements

}until (condition)

Control comes out of the loop when the condition is TRUE


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Intro to Perl 1-42


What is the output of the above code if the input isJoe

What is the output of the above code if the inputs

is Exit

Prints Hello Joe

Prints Hello Exit

do {

$Text=;

chomp $Text;

if($Text ne "Exit") {

print "\nHello ".$Text;

}}until($Text eq "Exit");


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Intro to Perl 1-45

PERL Control Structures contd#Purchase a max of 12 coupons

#for7 Days Or 6 Coupons for 3#Days

$Day=1;

$TotalCoupons=0;

while($Day12) {

$Day=1;

$TotalCoupons=0;

redo; #Restart the loop}

if ((($TotalCoupons+$Coupon)>6)&& Day


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Intro to Perl 1-46


Expression Modifiers if modifier can be tagged to an expression. Expression is evaluated only if the

condition is true

expression if (condition);

print "Enter the Salary: ";

$Salary = ;

$Incentive = $Salary*.20 if($Salary>0);

print "Incentive : $Incentive" if($Incentive>0);


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Intro to Perl 1-47

PERL Control Structures

exit used to terminate the execution of a script

exit 0 denotes success and exit 1 denotes failure

cannot display error messages while exiting

$Choice=

if ($Choice==4) { exit 0};

die displays the error message to STDERR stream

and terminates the execution of a script

copy($TargetFile,$SourceFile) or die File cannot be copied


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Intro to Perl 1-48

PERL - Arrays

Set of scalar values Dynamically grows/shrinks when ever required Prefixed with @ symbol Can store dissimilar data types Un initialized locations and locations beyond the end of array will be

undef Index starts from 0 Last index is denoted by $# Can be initialized using

List qw operator

Repetition operator (X) Range operator (..) Individual locations


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Intro to Perl 1-49

PERL Arrays contd

Creation

Or

Or

Or

@EmpName = (John,Dave,Mary,Jim);

@EmpNumber = (1001,1005,1008,1009);

@EmpName = qw (John Dave Mary Jim)

$EmpName[0] = John;

$EmpName[1] = Dave;

$EmpName[2] = Mary;

$EmpName[3] = Jim;

for($Loop=0;$Loop


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Intro to Perl 1-50

PERL Arrays contd

Creation using Range operator@EmpNumber = (1001..1200) ;

- Can be used if array has to be initialized by a range of elements

Creation using Repetition operator@Number = (0) X 10;- Can be used if array has to be initialized by same value in all locations

Creation of array with dissimilar elements@Details=(1001,John,3400.50);


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Intro to Perl 1-51

PERL Arrays contd

Displaying the array elements@Number=(101,102,103,104); To print the whole array

To print the individual elements

- To print the elements using a loop

101102103104

101,102,103,104

print @Number;

print join(,,@Number);

print $Number[0];

print $Number[1];

print $Number[2];

print $Number[3];

@Emp=(1..5);foreach $i (0..4) {

print $Emp[$i];

print " ";

}

1 2 3 4 5

101102103104


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Intro to Perl 1-52

PERL Arrays contd

Length of the array $# stores the last index of the array

$# +1 will give the number of elements

Emptying an array

$#Emp = -1;

OR@Emp = ( );

OR

@Emp = undef;

3

@Emp=(1001,1002,1003);

$NoElements=$#Emp+1;

print "No of elements=$NoElements";


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Intro to Perl 1-53

PERL Arrays contd

Pushing and Popping elements push (, /)

Will add the element to the end of array

Array expands automatically pop ()

Will remove the element from the end of the array

Array shrinks automatically

101,102

101,102,103

103

@Emp=(101,102);

print join(',',@Emp);

push (@Emp,103);


$No=pop(@Emp);

print \n.$No;


101,102


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Intro to Perl 1-54

PERL Arrays contd

Shifting and Unshifting unshift (, /) Will add the element/list to the front of the array & returns number

of elements

Array expands automatically shift ()

Will remove the element from front of the array Array shrinks automatically

101,102

100,101,102

100

101,102

@Emp=(101,102);


unshift (@Emp,100);


$No=shift(@Emp);

print $No;



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Intro to Perl 1-55

PERL Arrays contd

Merging of arrays using push

Array Slices (Section of an array)

10,11,12,105,106,107

101,102,103,104

,1150,1151,1152

101,102,103,104

1150,1151,1152

@Emp=(101,102,103,104,1150,1151,1152);


@Senior=@Emp[0..3];

print join(',',@Senior);

@Junior=@Emp[4..6];

print join(',',@Junior);

@EmpOld=(10,11,12);

@EmpNew=(105,106,107);

push (@Emp,@EmpOld);

push (@Emp,@EmpNew);



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Intro to Perl 1-56

PERL Arrays Contd

Reversing an Array using reverse@

Sorting an Array using sort @

Dave, Jim, John, Mary

104,103,102,101

@Name=("Jim","John","Dave","Mary");

@Name=sort @Name;

print join(',',@Name);

@List=(101,102,103,104);

@rList=reverse (@List);

print join(',',@rList);


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Intro to Perl 1-58

Summary

Scalar Variables

Perl List

Display Functions

Operators Standard input using /

Strings and various string functions

Conditional constructs

Looping constructsMiscellaneous control statements

Arrays


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Thats all for today!

Any questions?

Thank you!

2. Intro to Perl

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