Nirmala Venkat: Created page with "'''>>Title of script''':''' How to use Perl Module Library (CPAN)''' '''Author: Nirmala Venkat''' '''Keywords: Perl Module Library (CPAN), modules, PERL, PERL programming, v..."

2015-12-18T11:07:40Z

Created page with "'''>>Title of script''':''' How to use Perl Module Library (CPAN)''' '''Author: Nirmala Venkat''' '''Keywords: Perl Module Library (CPAN), modules, PERL, PERL programming, v..."

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'''>>Title of script''':''' How to use Perl Module Library (CPAN)'''

'''Author: Nirmala Venkat'''

'''Keywords: Perl Module Library (CPAN), modules, PERL, PERL programming, video tutorial'''

{| style="border-spacing:0;"
| style="background-color:#c0c0c0;border:1pt solid #000000;padding:0.097cm;"| '''Visual Cue'''
| style="background-color:#c0c0c0;border:1pt solid #000000;padding:0.097cm;"| '''Narration'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 1:

| style="border:1pt solid #000000;padding:0.097cm;"| Welcome to the''' Spoken Tutorial''' on''' How to use Perl Module Library (CPAN).'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 2:

Learning objectives
| style="border:1pt solid #000000;padding:0.097cm;"| In this tutorial we will learn to

* Use existing '''modules''' and
* Create new '''modules'''
in''' PERL'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 3:
System Requirements
| style="border:1pt solid #000000;padding:0.097cm;"| To record this tutorial, I am using
* '''Ubuntu Linux 12.04''' operating system
* '''Perl 5.14.2 and'''
* '''gedit''' Text Editor

You can use any text editor of your choice.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 4:

Pre-requisites

| style="border:1pt solid #000000;padding:0.097cm;"| To follow this tutorial, you should have working knowledge of''' Perl''' programming.

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 5a:

'''Modules '''
| style="border:1pt solid #000000;padding:0.097cm;"| '''Modules '''
* These are code files that contain common routines
* That are written by different authors
* And can be used by several programs at a time

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 5b:

'''CPAN (Comprehensive Perl Archive Network) '''
| style="border:1pt solid #000000;padding:0.097cm;"| '''CPAN'''

* '''PERL''' is an open source language and anyone can contribute to '''PERL's''' standard '''CPAN library'''
* '''CPAN '''has thousands of ready-to-use modules written by different authors

The official website of '''CPAN '''is www.cpan.org

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 6:

'''Modules : Example'''

| style="border:1pt solid #000000;padding:0.097cm;"| We will take''' List::Util''' as an example and see how to use it.

This gives me access to the functions which are already written inside this module.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to the''' terminal'''
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to the''' terminal.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Type''' perldoc List::Util'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| You may get an error saying ‘'''You need to install the perl hyphen doc package to use this program'''’

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Slide 7:

'''perl-doc Installation:'''

| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This indicates, you need to install the '''perl hyphen doc package.'''

Do so using '''Synaptic Package Manager.'''

Please refer to the relevant''' Linux''' spoken tutorials on the''' spoken tutorial''' website.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the output'''
| style="border:1pt solid #000000;padding:0.097cm;"| What you see here is the documentation for the''' List::Util''' module.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Note that the documentation contains

* description of the module,
* example of how to use it
* and an overview.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Type 'q' to quit'''
| style="border:1pt solid #000000;padding:0.097cm;"| Hit the ''''Q'''' key to exit the '''perldoc viewer'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Next we will see how to use''' List::Util module''' in a '''Perl''' program.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let me open a sample program''' exist underscore modules.pl''' which I have already saved.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| In your''' exist underscore''' '''modules dot pl''' file, type the following code as displayed on the screen.

Let us understand the code now.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''<nowiki>#!/</nowiki>usr/local/bin/perl'''

'''use strict<nowiki>;</nowiki>'''

'''use warnings<nowiki>;</nowiki>'''

'''use List::Util qw(first max maxstr min minstr reduce shuffle sum);'''

| style="border:1pt solid #000000;padding:0.097cm;"| '''use List::Util''' tells '''Perl '''to find and load the '''module List::Util.'''

'''qw()''' function extracts words out of the string using a '''delimiter '''and returns the words as a list.

It is just a quick way of declaring an '''array'''.

While importing a '''module''', it imports only the '''subroutines''' specified in the list into our program.

It contains general-utility list of '''subroutines'''.

The '''module '''will export its '''subroutines '''and '''variables '''into our program.

The most popular '''subroutines '''available in''' List::Util''' are:

'''first''' - which returns the first element in the list
'''max''' – returns the highest numerical value in the list

'''maxstr''' – returns the highest string in the list

'''min''' – returns the lowest numerical value

'''minstr''' – returns the lowest string in the list

'''shuffle''' – returns the values of the input in a random order

'''sum''' – returns the numerical sum of all the elements in the list

There is no need to write separate source code for each '''functions'''.

We can just make use of these available '''subroutines''' in our program.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''my $maximum = max 1..20; '''

'''my $minimum = min 3,9,12; '''

'''my $total = sum 1..100;'''

'''my $random =shuffle 0..51;'''
| style="border:1pt solid #000000;padding:0.097cm;"| These are the inputs I am passing to the function '''max, min, sum '''and''' shuffle.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''print "Maximum value:", $maximum , "\n";'''

'''print "Minimum value:", $minimum , "\n";'''

'''print "Sum of 1 to 100:", $total, "\n";'''

'''print "Random number:", $random, "\n";;'''
| style="border:1pt solid #000000;padding:0.097cm;"| And these are the '''print '''statements.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Press''' Ctrl+S'''
| style="border:1pt solid #000000;padding:0.097cm;"| Now, press''' Ctrl+S''' to save the file.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us execute the program.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Switch back to the''' terminal''' and type

'''perl exist underscore modules dot pl'''
and press''' Enter'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the output'''

Maximum value: 20

Minimum value: 3

Sum of 1 to 100: 5050

Random number: 41
| style="border:1pt solid #000000;padding:0.097cm;"| Observe the output.

In '''Random number''', you may get any value between 0 and 51.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Next we will see how to create new '''Perl modules''' and add it to '''CPAN'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 8:

'''Steps in creating a module:'''

| style="border:1pt solid #000000;padding:0.097cm;"| Below are the steps to create a '''module''':

* Create a place to develop the '''module'''
* Create skeleton files for the '''module'''
* Document the '''module'''
* Write the '''Perl code'''
* Write the code for testing
* Distribute the '''module '''in '''CPAN'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| '''Perl''' is distributed with a program called''' h2xs''' which is used to generate files for a new '''module'''.
'''Math::Simple''' specifies our '''module''' name.

This is used to generate the directory, which should clearly identify the '''module''' it contains.

Basically, it creates skeleton files for the '''module'''.

'''-PAX''' are options that omit autoload and autogenerate.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let's create a new '''module Math::Simple.'''

It will be provided with simple functions:''' add, subtract, multiply '''and '''divide'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us switch to '''terminal''' to execute the''' h2xs''' command.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Type,

'''h2xs -PAXn Math::Simple'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the files'''

'''Writing Math-Simple/lib/Math/Simple.pm'''

'''Writing Math-Simple/Makefile.PL'''

'''Writing Math-Simple/README'''

'''Writing Math-Simple/t/Math-Simple.t'''

'''Writing Math-Simple/Changes'''

'''Writing Math-Simple/MANIFEST'''

| style="border:1pt solid #000000;padding:0.097cm;"| The '''h2xs program''' generates all these files required to distribute the '''module'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''$ cd Math-Simple'''
| style="border:1pt solid #000000;padding:0.097cm;"| Let us change directory to''' Math hyphen Simple (Math-Simple)'''

Note the '''directory''' path on your machine.

It may be as''' Math forward slash Simple'''.('''Math/Simple)'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''$ ls'''
'''Changes lib Makefile.PL MANIFEST README t'''
| style="border:1pt solid #000000;padding:0.097cm;"| Type''' ls''' to list all the files in the '''directory.'''
We can see the following files.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' Changes'''
| style="border:1pt solid #000000;padding:0.097cm;"| The''' changes''' file is
* where we will keep track of changes made to our '''module '''
* when we write new versions.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' lib'''
| style="border:1pt solid #000000;padding:0.097cm;"| '''lib subdirectory '''contains the '''module'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' MANIFEST'''
| style="border:1pt solid #000000;padding:0.097cm;"| '''MANIFEST''' contains a list of files in this '''directory'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' Makefile.PL'''
| style="border:1pt solid #000000;padding:0.097cm;"| '''Makefile''' is a '''Perl '''program used to create a '''Unix Makefile'''.
We will use this '''Makefile''' to test and install our '''module'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' t'''
| style="border:1pt solid #000000;padding:0.097cm;"| Test scripts will be in''' t subdirectory.'''

The tests are simple '''Perl scripts''' but with a''' .t''' extension used for '''unit testing'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' Simple.pm'''
| style="border:1pt solid #000000;padding:0.097cm;"| '''Simple.pm''' is our '''module'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| All these files are generated automatically when we execute the h2xs command.
|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"|
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us open the''' simple.pm''' file.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to Terminal
'''cd lib/Math'''
| style="border:1pt solid #000000;padding:0.097cm;"| Change the '''directory''' to''' lib/Math'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"| >> '''gedit Simple.pm'''
| style="border:1pt solid #000000;padding:0.097cm;"| Now we will open the''' simple.pm''' file to see the existing content.

Type''' gedit Simple.pm'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight the existing content
| style="border:1pt solid #000000;padding:0.097cm;"| What we see here is a documented functional '''Perl module '''that doesn't do anything.

We have to write the required functions in this file to make it do something.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' Preloaded methods go here'''
| style="border:1pt solid #000000;padding:0.097cm;"| Add the below code after the text,''' Preloaded methods go here.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| <nowiki># </nowiki>Preloaded methods go here.

| style="border:1pt solid #000000;padding:0.097cm;"| Here we will add four subroutines''' add, subtract, multiply '''and '''divide'''.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now, press''' Ctrl+S''' to save the file.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now let's create a sample Perl program to test our code that make sure it is working properly.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us open the test file''' Math-Simple.t''' under subdirectory '''t.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Type '''gedit Math-Simple.t'''
| style="border:1pt solid #000000;padding:0.097cm;"| Type '''gedit Math-Simple.t'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''print "Addition:",add(19,23)."\n";'''

'''print "Subtraction:",subtract(100,23)."\n";'''

'''print "Multiply:",multiply(15,25)."\n";'''

'''print "Division:",divide(100,25)."\n";'''
| style="border:1pt solid #000000;padding:0.097cm;"| Add the following code after''' '''the existing code, '''“Insert your test code below”,'''

Print statements will print the output.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Press Ctrl +S
| style="border:1pt solid #000000;padding:0.097cm;"| Now, press''' Ctrl+S''' to save the file.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us run the test script.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Type perl t/Math-simple.t'''
| style="border:1pt solid #000000;padding:0.097cm;"| Type''' perl Math-simple.t '''and''' '''press''' Enter.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the error'''

| style="border:1pt solid #000000;padding:0.097cm;"| We see this error message because the '''Perl '''script cannot find '''Simple.pm''' in its directory.

It should look inside the''' lib'''/ directory.

How can we rectify this error?
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Let us see a few options for this.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 10:

'''@INC'''

'''Change @INC from inside the script'''

syntax:
use lib “path”

Example:
'''use''' lib t/Math-simple.t

or

Begin {'''unshift''' (@INC , t/Math-simple.t )}

'''Change @INC from the command line'''

Example:

perl''' -Ilib''' t/Math-Simple.t
| style="border:1pt solid #000000;padding:0.097cm;"| '''At the rate INC''' is a special variable that contains a list of directories.
'''Perl modules '''and '''libraries '''can be loaded from these directories.

This line of code tells the '''Perl''' program to add this '''directory path''' to its''' at the rate INC''' search directory.

Alternately, we can add files to''' at the rate INC''' at runtime using''' -I''' option.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to the terminal
| style="border:1pt solid #000000;padding:0.097cm;"| Now let us switch to the '''terminal'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| I will execute the program using the -I '''command line parameter'''

So, I will type

'''perl -Ilib t/Math-Simple.t'''
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the output'''

1..1

ok 1 - use Math::Simple<nowiki>;</nowiki>
Addition:42
Subtraction:77
Multiply:375
Division:4
| style="border:1pt solid #000000;padding:0.097cm;"| Here is the output as expected.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| We have tested the module and it is working fine.
Final step is to distribute the module.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Slide 11:'''
'''Distribute the Module'''
'''Run these commands from the terminal:'''

'''perl Makefile.PL'''
'''make'''
'''make test'''
'''make dist'''
| style="border:1pt solid #000000;padding:0.097cm;"| The general procedure for installing module is to run these commands.
Installation involves copying files into the Perl library directory.

Most of us don't have permission to copy into this directory.

Since '''Math-Simple''' isn't a very useful module I am not demonstrating the installation part.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| This brings us to the end of this tutorial. Let us summarise.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 12:
summary
| style="border:1pt solid #000000;padding:0.097cm;"| In this tutorial we learnt to

* Use existing '''modules'''
* Create new '''modules'''
and how to use in the Perl program.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 13:
Assignment
| style="border:1pt solid #000000;padding:0.097cm;"| Here is an assignment for you.
# Use the''' Text::Wrap''' module
# Make use of the''' Wrap()''' function which wraps the input text to form neat paragraphs.
# '''Text::Wrap''' module has a variable''' columns.''' Set the''' columns''' value to''' 30.'''
# Print the text to see the formatted output.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 14:
About Spoken Tutorial project

| style="border:1pt solid #000000;padding:0.097cm;"| The video at the following link summarises the Spoken Tutorial project.
Please download and watch it
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 15:
Spoken Tutorial workshops
| style="border:1pt solid #000000;padding:0.097cm;"| The''' Spoken Tutorial Project''' Team
* conducts workshops using spoken tutorials
* and gives certificates on passing online tests.
For more details, please write to us.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 16:
Acknowledgement
| style="border:1pt solid #000000;padding:0.097cm;"| Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at
this link.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| This is Nirmala Venkat from IIT Bombay, signing off. Thanks for watching.
|}

PERL/C3/Perl-Module-Library-(CPAN)/English - Revision history

Nirmala Venkat: Created page with "'''>>Title of script''':''' How to use Perl Module Library (CPAN)''' '''Author: Nirmala Venkat''' '''Keywords: Perl Module Library (CPAN), modules, PERL, PERL programming, v..."