Difference between revisions of "PERL/C3/Perl-Module-Library-(CPAN)/English-timed"

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|The official website of '''CPAN '''is:
 
|The official website of '''CPAN '''is:
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www.cpan.org
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'''www.cpan.org'''
  
 
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|Type:''' perldoc List colon colon Util'''
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|Type:''' perldoc List colon colon Util'''.
  
 
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|This indicates, you need to install the '''perl hyphen doc package.'''
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|This indicates, you need to install the '''perl hyphen doc''' package.
  
 
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* description of the module,  
 
* description of the module,  
 
* example of how to use it  
 
* example of how to use it  
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* and an overview.
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* and an '''overview'''.
  
 
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|Next, we will see how to use''' List colon colon Util module''' in a '''Perl''' program.
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|Next, we will see how to use''' List colon colon Util''' module in a '''Perl''' program.
  
 
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|'''use List colon colon Util''' tells '''Perl''' to find and load the '''module List colon colon Util.'''
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|'''use List colon colon Util''' tells '''Perl''' to find and '''load''' the module '''List colon colon Util.'''
  
 
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|The most popular '''subroutines '''available in''' List colon colon Util''' are:
 
|The most popular '''subroutines '''available in''' List colon colon Util''' are:
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'''first''' - which returns the first element in the list.
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'''first''' - which returns the first '''element''' in the '''list'''.
  
 
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|'''shuffle''' – returns the values of the input in a random order.
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|'''shuffle''' – this returns the values of the '''input''' in a random order.
  
 
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|Next we will see how to create new '''Perl modules''' and add it to '''CPAN'''.
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|Next, we will see how to create a new '''Perl module''' and add it to '''CPAN'''.
  
 
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|Type: '''h2xs hyphen PAXn Math colon colon Simple'''
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|Type: '''h2xs hyphen PAXn Math colon colon Simple'''.
  
 
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|The '''h2xs program''' generates all these files required to distribute the module.
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|The '''h2xs''' program generates all these files required to distribute the module.
  
 
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|The "Changes" file is where we will keep track of changes made to our module when we write new versions.
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|The "Changes" file is where we will keep track of changes, made to our module, when we write new versions.
  
 
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|'''lib subdirectory '''contains the '''module'''.
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|'''lib subdirectory '''contains the module.
  
 
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|We will use this '''Makefile''' to test and install our '''module'''.
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|We will use this '''Makefile''' to test and install our module.
  
 
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|Test scripts will be in''' 't' subdirectory.'''
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|'''Test script'''s will be in''' 't' subdirectory.'''
  
 
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|The tests are simple '''Perl scripts''' but with a''' dot t extension''' used for '''unit testing'''.
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|The '''tests''' are simple '''Perl scripts''', but with a''' dot t extension''' used for '''unit testing'''.
  
 
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|All these files are generated automatically when we execute the '''h2xs command.'''
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|All these files are generated automatically when we execute the '''h2xs''' command.
  
 
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|Type:''' gedit Simple.pm'''
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|Type:''' gedit Simple.pm'''.
  
 
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|What we see here is a documented, functional '''Perl module '''that doesn't do anything.
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|What we see here is a documented, functional Perl module that doesn't do anything.
  
 
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|Here we will add four subroutines''' add, subtract, multiply '''and '''divide'''.
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|Here, we will add four subroutines''' add, subtract, multiply '''and '''divide'''.
  
 
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|Add the following code after the existing code, “Insert your test code below..”.
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|Add the following code after the existing code: “Insert your test code below..”.
  
 
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|Let us '''run''' the test script.
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|Perl modules and '''libraries '''can be '''load'''ed from these directories.
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|Perl modules and '''libraries '''can be loaded from these directories.
  
 
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|The video at the following link summarizes the Spoken Tutorial project.
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|The video at the following link summarizes the '''Spoken Tutorial''' project.
 
Please download and watch it.
 
Please download and watch it.
  

Revision as of 13:02, 18 July 2016

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

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