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

|Welcome to the''' Spoken Tutorial''' on how to use '''Perl Module Library'''  i.e. '''CPAN'''

|In this tutorial, we will learn to use existing '''modules''' and create new modules in''' PERL'''.

|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.

|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.

|'''Modules: '''

* And, can be used by several programs at a time.

|'''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'''

|We will take''' List colon colon Util''' as an example and see how to use it.

|This gives me access to the '''function'''s which are already written inside this module.

|Switch to the''' terminal.'''

|Type:''' perldoc List colon colon Util'''.

| You may get an '''error''' saying '''You need to install the perl hyphen doc package to use this program'''.  

|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.

|What you see here is the documentation for the''' List colon colon Util''' module.

|Note that the documentation contains-

* description of the module,  

* and an '''overview'''.

|Hit the 'Q' key to exit the '''perldoc viewer'''.

|Next, we will see how to use''' List colon colon Util''' module in a '''Perl''' program.

|Let me open a sample program''' exist underscore modules.pl''' which I have already saved.

|In your''' exist underscore modules dot pl''' file, type the following code as displayed on the screen.

|Let us understand the code now.

|'''use List colon colon Util''' tells '''Perl''' to find and '''load''' the module '''List colon colon 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 '''import'''s 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 colon colon Util''' are:

'''first''' - which returns the first '''element''' in the '''list'''.

|'''max''' –this returns the highest numerical value in the list.

|'''maxstr'''- returns the highest '''string''' in the list.

|'''min'''- this returns the lowest numerical value.

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

|'''shuffle''' – this 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 '''function'''.

|We can just make use of these available '''subroutines''' in our program.

|These are the '''input'''s I am passing to the function '''max, min, sum '''and''' shuffle.'''

|And, these are the '''print '''statements.

|Now, press''' Ctrl+S''' to '''save''' the file.

|Let us '''execute''' the program.

|Switch back to the terminal and type:  '''perl exist underscore modules dot pl''' and press''' Enter'''.

|Observe the '''output'''.

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

|Next, we will see how to create a new '''Perl module''' and add it to '''CPAN'''.

|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'''.

|'''Perl''' is distributed with a program called''' h2xs''' which is used to generate files for a new module.

|'''Math colon colon 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.

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

|Let's create a new module- '''Math colon colon Simple.'''

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

|Let us switch to terminal to execute the''' h2xs''' command.

|Type: '''h2xs hyphen PAXn Math colon colon Simple'''.

|The '''h2xs''' program generates all these files required to distribute the module.

|Let us change directory to''' Math hyphen Simple'''.

|Note the '''directory path''' on your machine. It may be as''' Math forward slash Simple'''.

|Type "ls" to list all the files in the directory. We can see the following files.

|The "Changes" file is where we will keep track of changes, made to our module, when we write new versions.

|'''lib subdirectory '''contains the module.

|'''MANIFEST''' contains a list of files in this directory.

|'''Makefile''' is a Perl program used to create a '''Unix Makefile'''.  

|We will use this '''Makefile''' to test and install our module.

|'''Test script'''s will be in''' 't' subdirectory.'''

|The '''tests''' are simple '''Perl scripts''', but with a''' dot t extension''' used for '''unit testing'''.

|'''Simple.pm''' is our module.

|All these files are generated automatically when we execute the '''h2xs''' command.

|  Let us open the''' simple.pm''' file.

|Change the directory to''' lib forward slash Math'''.

|Now, we will open the''' simple.pm''' file to see the existing content.

|Type:''' gedit Simple.pm'''.

|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.

|Add the below code after the text: "Preloaded methods go here".

|Here, we will add four subroutines''' add, subtract, multiply '''and '''divide'''.

|Now, press''' Ctrl+S''' to '''save''' the file.

|Now, let's create a sample Perl program to test our code that makes sure it is working properly.

|Let us open the test file''' Math-Simple.t''' under the subdirectory 't'.

|Type: '''gedit Math-Simple.t'''

|Add the following code after the existing code: “Insert your test code below..”.

| The '''Print''' statements will print the output.

|Now, press''' Ctrl+S''' to '''save''' the file.

|Let us '''run''' the '''test script'''.

|Type:''' perl Math-simple.t '''and press''' Enter.'''

|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?

|Let us see a few options for this.

|'''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 run time using '-I' option.

|Now, let us switch to the terminal.

|I will '''execute''' the program using the''' '-I' command line parameter'''.

|So, I will type: '''perl -Ilib t/Math-Simple.t'''

|Here is the output as expected.

|We have tested the module and it is working fine.  

|Final step is to distribute the module.

|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.

|This brings us to the end of this tutorial. Let us summarize.

|In this tutorial, we learnt to:

|Here is an assignment for you.

|Use the''' Text colon colon Wrap''' module.

| Make use of the''' Wrap()''' function which wraps the input text to form neat paragraphs.

| '''Text colon colon Wrap''' module has a variable- "columns". Set the''' columns''' value to 30.

| Print the text to see the formatted output.

|The video at the following link summarizes the '''Spoken Tutorial''' project.

Please download and watch it.

|The''' Spoken Tutorial Project''' team:

* and gives certificates on passing online tests.

|For more details, please write to us.

|Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.

|More information on this mission is available at this link.

|This is Nirmala Venkat from '''IIT Bombay''', signing off. Thanks for watching.