Difference between revisions of "PERL/C3/Including-files-or-modules/English"

Learning objectives

• do method
• use method
• require method

• do
• use and
• require

methods in PERL programming.

System Requirements

• Ubuntu Linux 12.04 operating system
• Perl 5.14.2 and
• gedit Text Editor

You can use any text editor of your choice.

Pre-requisites

If not, then go through the relevant Perl spoken tutorials on the spoken tutorial website.

do file name / module name

These are simple ways to include the source code from other files into the current script file.

$datestring = localtime();

sub msgThanks {

print("Thank you...\n");

}

Here, I have a function by name msgThanks, which returns a “Thank you” message.

print "Welcome to Spoken tutorials!! \n";

print "\n";

do "datetime.pl";

print ("Have a nice day! \n");

print ("Today's date: $datestring \n");

msgThanks();

do() method is called with the filename from where we want to use the code.

Current date and time is stored in the $datestring variable of datetime dot pl file.

And at the end, we call the msgThanks() function from the same file.

perl main dot pl and press Enter

Welcome to Spoken tutorials!!

Have a nice day! Today's date: Thu Aug 13 10:57:15 2015 Thank you...

require and use methods

• when we have collections of subroutines
• that can be used in multiple Perl programs.

use method:

• use method is used only for the modules.
• It is verified at the time of compilation
• There is no need to give the file extension

require method:

• require method is used for both Perl programs and modules
• It is verified at the run time
• One needs to give the file extension.

use module name;

• The syntax of use method is

use module name semicolon

• Perl modules are the files which end with .pm extension.
• Reusability of code is implemented through modules.
• These are similar to libraries in other languages.

sub total {

my $sum = 0;

foreach my $num(@_){

$sum =$sum+ $num;

}

print "The total is : $sum\n";

}

1;

Let me explain the code now.

use sum;

total(1, 7, 5, 4, 9);

total(1...10);

In our case, the module name is sum.

We are passing 1,7,5,4,9 as input parameters to the function total in sum dot pm file.

Again, in the next line, we are passing 1 to 10 as input parameters to the same function.

perl app dot pl

The total is 26

The total is 55

Switch back to sum.pm in the text editor.

use strict; use warnings;

use strict semicolon

use warnings semicolon

use strict;

use warnings;

sub total {

my $sum = 0;

foreach my $num(@_){

$sum =$sum+ $num;

}

print "The total is : $sum\n";

}

1;

These are used to avoid common programming mistakes.

use strict forces the user to declare all the variables used in the program.

If there are errors, use strict will abort the execution.

use warnings will only provide warnings but continue with the execution.

$sum =0;

Let us now see how the same program is executed.

perl app dot pl

Global symbol "$sum" requires explicit package name at sum.pm line 8.

Global symbol "$sum" requires explicit package name at sum.pm line 9.

Global symbol "$sum" requires explicit package name at sum.pm line 10.

Compilation failed in require at app.pl line 5.

BEGIN failed--compilation aborted at app.pl line 5.

The first set of lines displayed on the terminal are error messages generated by “use strict”.

The last two are the abort messages.

Let us understand the code now.

my ($number) = @_;

return ($number * $number);

}

sub square_root() {

my ($number) = @_;

return (sqrt($number));

}

sub random_number() {

my ($number) = @_;

return (rand($number));

}

# generate a random number in perl between a range of numbers

sub random_range() {

my ($lrange, $urange) = @_;

return int(rand($urange-$lrange))+ $lrange;

}

1;

The first function square() returns the square of a number.

The second function square underscore root() returns the square root of a given number.

Next function random underscore number() generates a random number.

The last function random underscore range() generates a random number between a lower range and upper range of numbers.

Note that we need the 1 semicolon at the end of the file.

This is because Perl needs the last expression in the file to return a true value.

Let me explain the code now.

use strict;

use warnings;

require 'commonfunctions.pl';

print "1.Square of a number \n";

print "2.Square root of a number \n";

print "3.Random number in the given range\n";

print "4.Quit \n";

print "Enter the Option: ";

my $option = <>;

if ($option == 1)

{

# Find a square of a number

print "Enter a number: ";

my $number = <>;

print "Square of $number is: " .square($number) . "\n";

}

elsif ($option == 2)

{

# Find a square root of a number

print "Enter a number: ";

my $number1 = <>;

print "Squareroot of $number1 is:" .square_root($number1) . "\n";

}

elsif ($option == 3)

{

# Find a random number in the given range

print "Enter a lower range: ";

my $lower = <>;

print "Enter a upper range:";

my $upper = <>;

print "Random number in the given range is: " .random_range($lower,$upper) . "\n";

}

elsif ($option == 4)

{ exit;

}

else { print "Incorrect option. Exiting the program \n";

}

This program gives 4 options to the user.

The user has to choose one option at a time.

One is to find the square of a number.

Two is for square root of a number.

Three is for a random number in the given range.

Four is to quit the program.

If option one is typed, it will ask the user to enter a number.

The value is stored in $number.

This is passed to the function square in commonfunctions.pl file.

The function returns the square of a number.

The print statement prints the square of a number as output.

If option two is typed, the square root of a number is displayed as output.

The execution is followed as explained in the previous function square.

If option three is typed, a random number is displayed as output in the given range.

Else if option is four, the program exits.

If any option other than the ones specified is given, the print statement says “Incorrect option”.

Note that in this program we have called only three functions out of four from commonfunctions.pl.

perl callprogram dot pl

1.Square of a number

2.Square root of a number

3.Random number in the given range

4.Quit

Enter the Option: 2

Enter a number: 169

Square root of 169 is: 13

1.Square of a number

2.Square root of a number

3.Random number in the given range

4.Quit

Enter a upper range: 99

Enter a upper range as 99.

Summary

• do
• use
• require

methods in PERL programming.

Note: "use Module" is recommended over "require Module", because it determines module availability at compile time.

Assignment

1. Write a Perl program reminder.pl where you will write a letter to the participants.
2. Prompt the user to enter To and From name
3. Call the subroutines from Letter.pm using ‘use’ method.
4. Write the below functions in Letter.pm file.

• LetterDate() function returns the current date and time
• To() function returns the name of the participants
• From() function returns the sender name
• Lettermsg() function returns the content of the letter
• Thanksmsg() function returns thanks and regards.

Output

To: Mr. Ram, 23 Gandhi Nagar, Mumbai-400034.

From: Vikash

Date: Thu Aug 13 11:25:29 2015

Greetings!!

This is to remind you that your registration fees of Rs. 500.00 is pending.

If you have not yet made the payment, kindly do so immediately.

Thanks and regards,

Vikash.

About Spoken Tutorial project

Please download and watch it

Spoken Tutorial workshops

• conducts workshops using spoken tutorials and
• gives certificates on passing online tests.

For more details, please write to us.

Acknowledgement

More information on this mission is available at

this link.