PERL/C2/Conditional-statements/English

Title Of Script: if, if-else statements in Perl

Author: Amol Brahmankar

Keywords: Conditional Statements in Perl, if statement in perl, if-else statement in perl, video tutorial.

Visual Clue	Narration
Slide	Welcome to the spoken tutorial on if and if-else conditional statements in Perl.
Slide: Learning Objectives	In this tutorial, we will learn about; if statement and if-else statement in Perl
Slide: System Requirements	I am using Ubuntu Linux12.04 operating system and Perl 5.14.2 I will also be using the gedit Text Editor. You can use any text editor of your choice.
Slide: Prerequisites	You should have basic knowledge of Variables and Comments in Perl Knowledge of for, foreach, while and do-while loops in Perl will be an added advantage. Please go through the relevant spoken tutorials on the spoken tutorial website.
Slide	Perl provides the following conditional statements - 1. if 2. if-else 3. if-elsif-else and 4. switch In this tutorial, we'll cover if and If-else statements
Slide	if statement in Perl can be used to execute a piece of code only when a specified condition is satisfied.
Slide if (condition) { piece of code; }	The syntax of if conditional statement is as follows if space open bracket condition close bracket space Open curly bracket Enter Piece of code to be executed when the condition is true semicolon Enter Close curly bracket
Highlight if (condition)	The code inside the if statement will be executed only when the condition is true.
	Now let us look at an example of if statement.
Switch to the Terminal and type gedit conditionalBlocks.pl & and press Enter.	Open the Terminal and type gedit conditionalBlocks dot pl space ampersand and press Enter
Point to the filename conditionalBlocks.pl in the Titlebar of gedit. Type the piece of code. #!/usr/bin/perl $count = 5; if ($count == 5) { print “I am inside if statement\n”; }	This will open the conditionalBlocks.pl file in gedit. Type the following piece of code as displayed on the screen. Here we have specified a condition for if which checks the value of variable count.
Highlight ==	Note the equal to equal to sign here. This is the comparison operator.
Highlight if ($count == 5)	The condition $count equal to equal to 5 is checked against the value of variable count. When it is equal to 5, the code within the if block will get executed.
Press Ctrl S	Now, press ctrl+s to save the file.
Switch to terminal	Then switch to the terminal. Make sure that you are in the directory in which you have saved your file.
perl -c conditionalBlocks.pl	Type the following to check for any compilation or syntax error - perl hyphen c conditionalBlocks dot pl and press Enter.
Highlight the below line on terminal- conditionalBlocks.pl syntax OK	The following line will be displayed on the terminal window conditionalBlocks.pl syntax OK
Execute Perl script perl conditionalBlocks.pl	As there is no compilation or syntax error, we will execute the Perl script by typing - perl conditionalBlocks dot pl and press Enter
Highlight the output on the terminal I am inside if statement	The following output will be shown on terminal. I am inside if statement
Switch back to gedit print “I am inside if statement\n” if ($count == 5);	Switch back to gedit Alternately, we can write the above if statement as- print space double quote I am inside if statement slash n double quote complete space if open bracket dollar count equal to equal to 5 close bracket semicolon.
	Now, let us look at if-else statement.
Slide	This statement is used when user wants to execute one piece of code when the condition is true and another piece of code when the condition is false
Slide if-else statement syntax is if (condition) { piece of code; # executes when if condition is true } else { another piece of code; # executes when if condition is false }	The syntax for if-else condition is as follows - if space open bracket condition close bracket space open curly bracket Press Enter piece of code semicolon to be executed when if condition is true, Press Enter close curly bracket space else space open curly bracket Enter another piece of code semicolon to be executed when if condition is false Press Enter close curly bracket
Switch to gedit #!/usr/bin/perl $count = 4; if ($count == 5) { print “I am inside if statement\n”; } else { print “I am inside else statement\n”; }	Now again, go to the conditionalBlocks.pl file which we have already created in gedit. at the end of the if block type space else space open curly bracket press Enter print space double quote I am inside else statement slash n close double quote semicolon Press Enter and close the curly bracket.
Highlight $count = 4;	Here, 4 is assigned to variable count.
Highlight if ($count == 5)	As the value of count variable does not match 5, the code within the if block will not get evaluated instead the code within the else block will get evaluated.
Press Ctrl+s	Now press Ctrl+S to save the file.
Switch to terminal	Now switch to terminal.
perl -c conditionalBlocks.pl and press Enter	Then compile the file for any syntax or compilation errors by typing perl hyphen c conditionalBlocks dot pl and press Enter
Point to the below line on terminal - conditionalBlocks.pl syntax OK	The following line will be displayed on the terminal conditionalBlocks.pl syntax OK
Execute Perl script perl conditionalBlocks.pl and press Enter	As there is no compilation or syntax error, we will now execute the Perl script. Type perl conditionalBlocks dot pl and press Enter
Highlight output on the terminal I am inside else statement	The following output will be shown on terminal. I am inside else statement
Slide: Summary	Let us summarize. In this tutorial, we have learnt - if and if-else conditional statements in Perl using sample programs.
Slide: Assignment	Here is assignment for you - Print “It is an open source language” when the variable declared has value 'Perl' otherwise print “It's a proprietary language”
About the Project	Watch the video available at the following link It summaries the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Spoken Tutorial Workshops	The Spoken Tutorial Project Team Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact at spoken hyphen tutorial dot org
Acknowledgment http://spoken-tutorial.org\NMEICT-Intro	Spoken Tutorial Project is a part of the Talk to a Teacher project It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available spoken hypen tutorial dot org slash NMEICT hyphen Intro
	Hope you enjoyed this Perl tutorial. This is Amol Brahmankar signing off. Thanks for joining

Contributors and Content Editors

AmolBrahmankar, PoojaMoolya