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

Time	Narration
00:01	Welcome to the Spoken Tutorial on how to use Perl Module Library i.e. 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 – this 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 function.
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 a new Perl module 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. hyphen 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 makes 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 run time 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 summarizes 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