PERL/C3/Perl-Module-Library-(CPAN)/English-timed

Time	Narration
00:01	Welcome to the Spoken Tutorial on How to use Perl Module Library ie. CPAN
00:08	In this tutorial we will learn to use existing modules and Create new modules in PERL.
00:16	To record this tutorial, I am using Ubuntu Linux 12.04 operating system Perl 5.14.2 and gedit Text Editor
00:28	You can use any text editor of your choice.
00:32	To follow this tutorial, you should have working knowledge of Perl programming.
00:37	If not, then go through the relevant Perl spoken tutorials on the spoken tutorial website.
00:43	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
00:55	CPAN PERL is an open source language and anyone can contribute to PERL's standard CPAN library
01:03	CPAN has thousands of ready-to-use modules written by different authors
01:09	The official website of CPAN is www.cpan.org
01:17	We will take List colon colon Util as an example and see how to use it.
01:24	This gives me access to the functions which are already written inside this module.
01:30	Switch to the terminal.
01:32	Type perldoc List colon colon Util
01:38	You may get an error saying ‘You need to install the perl hyphen doc package to use this program’
01:46	This indicates, you need to install the perl hyphen doc package.
01:50	Do so using Synaptic Package Manager.
01:55	Please refer to the relevant Linux spoken tutorials on the spoken tutorial website.
02:01	What you see here is the documentation for the List colon colon Util module.
02:08	Note that the documentation contains description of the module, example of how to use it and an overview.
02:20	Hit the 'Q' key to exit the perldoc viewer.
02:25	Next, we will see how to use List colon colon Util module in a Perl program.
02:33	Let me open a sample program exist underscore modules.pl which I have already saved.
02:40	In your exist underscore modules dot pl file, type the following code as displayed on the screen.
02:47	Let us understand the code now.
02:50	use List colon colon Util tells Perl to find and load the module List colon colon Util.
03:00	qw() function extracts words out of the string using a delimiter and returns the words as a list.
03:09	It is just a quick way of declaring an array.
03:13	While importing a module, it imports only the subroutines specified in the list into our program.
03:21	It contains general-utility list of subroutines.
03:26	The module will export its subroutines and variables into our program.
03:32	The most popular subroutines available in List colon colon Util are: first - which returns the first element in the list
03:42	max –this returns the highest numerical value in the list
03:47	maxstr returns the highest string in the list
03:52	min this returns the lowest numerical value
03:57	minstr – returns the lowest string in the list
04:02	shuffle – returns the values of the input in a random order
04:08	sum – returns the numerical sum of all the elements in the list
04:14	There is no need to write separate source code for each functions.
04:18	We can just make use of these available subroutines in our program.
04:23	These are the inputs I am passing to the function max, min, sum and shuffle.
04:30	And these are the print statements.
04:33	Now, press Ctrl+S to save the file.
04:37	Let us execute the program.
04:40	Switch back to the terminal and type perl exist underscore modules dot pl and press Enter.
04:49	Observe the output.
04:51	In Random number, you may get any value between 0 and 51.
04:58	Next we will see how to create new Perl modules and add it to CPAN.
05:04	Below are the steps to create a module:
05:08	Create a place to develop the module
05:11	Create skeleton files for the module
05:14	Document the module
05:16	Write the Perl code
05:18	Write the code for testing
05:20	Distribute the module in CPAN
05:24	Perl is distributed with a program called h2xs which is used to generate files for a new module.
05:32	Math colon colon Simple specifies our module name.
05:37	This is used to generate the directory, which should clearly identify the module it contains.
05:43	Basically, it creates skeleton files for the module. hypen PAX are options that omit autoload and autogenerate.
05:54	Let's create a new module Math colon colon Simple.
05:59	It will be provided with simple functions: add, subtract, multiply and divide.
06:06	Let us switch to terminal to execute the h2xs command.
06:12	Type, h2xs hyphen PAXn Math colon colon Simple
06:20	The h2xs program generates all these files required to distribute the module.
06:27	Let us change directory to Math hyphen Simple
06:33	Note the directory path on your machine. It may be as Math forward slash Simple.
06:41	Type ls to list all the files in the directory. We can see the following files.
06:49	The changes file is where we will keep track of changes made to our module when we write new versions.
06:58	lib subdirectory contains the module.
07:02	MANIFEST contains a list of files in this directory.
07:07	Makefile is a Perl program used to create a Unix Makefile.
07:12	We will use this Makefile to test and install our module.
07:18	Test scripts will be in t subdirectory.
07:22	The tests are simple Perl scripts but with a dot t extension used for unit testing.
07:30	Simple.pm is our module.
07:34	All these files are generated automatically when we execute the h2xs command.
07:41	Let us open the simple.pm file.
07:45	Change the directory to lib forward slash Math
07:51	Now we will open the simple.pm file to see the existing content.
07:57	Type: gedit Simple.pm
08:02	What we see here is a documented functional Perl module that doesn't do anything.
08:09	We have to write the required functions in this file to make it do something.
08:16	Add the below code after the text, Preloaded methods go here.
08:22	Here we will add four subroutines add, subtract, multiply and divide.
08:29	Now, press Ctrl+S to save the file.
08:33	Now, let's create a sample Perl program to test our code that make sure it is working properly.
08:41	Let us open the test file Math-Simple.t under the subdirectory 't'.
08:49	Type: gedit Math-Simple.t
08:55	Add the following code after the existing code, “Insert your test code below”,
09:02	The Print statements will print the output.
09:06	Now, press Ctrl+S to save the file.
09:10	Let us run the test script.
09:13	Type: perl Math-simple.t and press Enter.
09:19	We see this error message because the Perl script cannot find Simple.pm in its directory.
09:27	It should look inside the lib directory. How can we rectify this error?
09:33	Let us see a few options for this.
09:37	At the rate INC is a special variable that contains a list of directories.
09:43	Perl modules and libraries can be loaded from these directories.
09:48	This line of code tells the Perl program to add this directory path to its at the rate INC search directory.
09:57	Alternately, we can add files to at the rate INC at runtime using -I option.
10:06	Now let us switch to the terminal.
10:10	I will execute the program using the -I command line parameter.
10:16	So, I will type: perl -Ilib t/Math-Simple.t
10:24	Here is the output as expected.
10:27	We have tested the module and it is working fine.
10:31	Final step is to distribute the module.
10:34	The general procedure for installing module is to run these commands.
10:40	Installation involves copying files into the Perl library directory.
10:45	Most of us don't have permission to copy into this directory.
10:49	Since Math-Simple isn't a very useful module, I am not demonstrating the installation part.
10:57	This brings us to the end of this tutorial. Let us summarize.
11:02	In this tutorial, we learnt to: Use existing modules Create new modules and how to use in the Perl program.
11:11	Here is an assignment for you.
11:13	Use the Text colon colon Wrap module.
11:17	Make use of the Wrap() function which wraps the input text to form neat paragraphs.
11:24	Text colon colon Wrap module has a variable- columns. Set the columns value to 30.
11:31	Print the text to see the formatted output.
11:35	The video at the following link summarises the Spoken Tutorial project. Please download and watch it.
11:42	The Spoken Tutorial Project team: conducts workshops using spoken tutorials and gives certificates on passing online tests.
11:51	For more details, please write to us.
11:55	Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.
12:02	More information on this mission is available at this link.
12:06	This is Nirmala Venkat from IIT Bombay, signing off. Thanks for watching.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14