Nancyvarkey at 11:35, 9 November 2015

2015-11-09T11:35:04Z

Nirmala Venkat at 12:02, 5 November 2015

2015-11-05T12:02:40Z

Nirmala Venkat: Created page with "'''Title of script''':''' Sample PERL Program''' '''Author: Nirmala Venkat''' '''Keywords: module, package, array, hash, functions, reference, dereference, PERL, PERL progra..."

2015-11-05T09:36:36Z

Created page with "'''Title of script''':''' Sample PERL Program''' '''Author: Nirmala Venkat''' '''Keywords: module, package, array, hash, functions, reference, dereference, PERL, PERL progra..."

New page

'''Title of script''':''' Sample PERL Program'''

'''Author: Nirmala Venkat'''

'''Keywords: module, package, array, hash, functions, reference, dereference, PERL, PERL programming, video tutorial'''

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

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

| style="border:1pt solid #000000;padding:0.097cm;"| Welcome to the''' Spoken Tutorial''' on''' Sample PERL program.'''

|-
| 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

* include all the major topics we covered so far
* in a sample Perl program
|-
| 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 the''' 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;"| As a prerequisite, you should have working knowledge of '''Perl''' Programming.

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

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

Program outline:

| style="border:1pt solid #000000;padding:0.097cm;"| The sample Perl program will give the output of various weather forecast reports of a region.

'''Weather.pm''' is a''' module''' file that has a complex data structure to hold the data required for this program.

It also contains various '''functions '''to generate the report.

'''Weather''' '''underscore report.pl''' is the''' perl''' program which makes use of this '''module '''file to give the required output.
|-
| 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;"| The same code files are available under this video of our website. Download and unzip the files provided in the code file link.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to the''' Weather.pm '''in''' gedit'''
| style="border:1pt solid #000000;padding:0.097cm;"| Now let us see our sample '''Perl '''program '''Weather dot pm.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the code line by line.'''

| style="border:1pt solid #000000;padding:0.097cm;"| The block of code in this program is under the '''namespace Weather'''.
'''Perl '''implements '''namespace '''using the''' package keyword.'''

'''BEGIN''' block is compiled and executed before the main program.

'''Export''' allows to export the '''functions''' and variables of '''modules''' to user's '''namespace'''.

'''At the rate EXPORT''' and''' at the rate EXPORT underscore OK''' are the two main variables used during export operation.

'''At the rate EXPORT''' contains list of '''subroutines''' and variables of the '''module.'''

These will be exported into the caller '''namespace.'''

'''At the rate EXPORT underscore OK''' does export of symbols on demand basis.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Here I have used''' references''' to create complex data structures to hold the data required for a weather report.

'''$weather_report''' is a''' hash reference''' with 5 keys.

“'''place'''” and “'''nstate'''” has the scalar values.

“'''weekly'''” is '''hash''' of''' hash references'''.

Each week day has four '''keys''' -

'''max underscore temp, min underscore temp, sunrise, sunset.'''

“'''record underscore time'''” is an''' array reference''' with two index values.
|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| I have a few '''subroutines''' to display the weather report of various options.

Let us see one by one.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' display_header()'''
| style="border:1pt solid #000000;padding:0.097cm;"| This function prints the header information such as header of the report, place, state and current date.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now let us see the next function''' display underscore daily underscore report.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' display_daily_report()'''

| style="border:1pt solid #000000;padding:0.097cm;"| This '''function '''prints the daily report on the screen depending upon the weekday input.

We retrieve the parameter passed into a '''subroutine''' using the''' shift function.'''

I have used the''' trim function''' to remove the leading and trailing spaces of the parameter value.

Here is the code for the '''trim''' '''function'''.

'''Lc function''' returns a lowercase version of the given input.

This is used to avoid case-sensitivity.

The week day passed as parameter from the main program, is assigned to a''' local variable''' '''dollar week underscore day'''.

The following '''print statements''' will print the data corresponding to a specified week day.

We are using the '''arrow operator''' to''' dereference''' a value in '''$weather underscore report'''.

When working with '''references''', we have to understand the '''data type '''we are '''dereferencing'''.

If it is a '''hash''', we need to pass the '''key '''in curly braces.

If it is an '''array,''' we need to use the square brackets with the index values.

'''return function''' of '''Perl''' returns a value.

This can be used to check the status of the '''function''' in the main program.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| The next '''function''' is''' write underscore daily underscore report.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' write_daily_report()'''
| style="border:1pt solid #000000;padding:0.097cm;"| This '''function''' will print the report output to a file.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| The''' open function''' with the greater than (>) symbol defines the''' WRITE''' mode.

Filename is created with the weekday name and '''dot txt '''extension.
|-
| style="border:1pt solid #000000;padding:0.097cm;"| '''Highlight the print statements'''
| style="border:1pt solid #000000;padding:0.097cm;"| The '''print statements''' will print the corresponding data of a specified week day to a file.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight''' display_weekly_report()'''
| style="border:1pt solid #000000;padding:0.097cm;"| This prints the weekly report.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| I have declared a '''foreach loop''' to loop through each weekday of the''' hash reference'''.

I have used curly brackets to represent the''' hash reference''' and the '''arrow '''operator to''' dereference'''.

I am using the''' “keys” built-in function '''to loop through the '''keys '''of the '''hash'''.

'''Display underscore daily underscore report function '''will print each element of the '''hash'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now let us see a '''Perl '''program '''weather underscore report dot pl '''where we will make use of this '''module '''file '''Weather dot pm'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight the code according to the narration.

| style="border:1pt solid #000000;padding:0.097cm;"| Here, '''use strict''' and''' use warnings''' are compiler flags that helps to avoid common programming mistakes.

'''use Weather semicolon.'''

Here '''Weather '''is a''' module''' name which I have used in this program.

We have already seen that the '''functions''' required for this program have been stored in this''' module'''.

It is not required to give the''' .pm''' file extension here.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| In this program, I'll print different reports depending upon the given options.

The user has to enter an option to print the

# daily weather report of a particular week day
# daily weather report of a particular week day to an output file
# weekly weather report

If option 1 is typed, it will ask the user to enter the day of a week.

The '''diamond '''operator will read from''' STDIN''', that is from the keyboard.

For example, if the user enters ''''monday'''', then it is assigned to a variable '''dollar dayoption, '''which is a''' local variable'''.

Next, we can see that we are calling two functions''' display_header()''' and''' display_daily_report().'''

We have exported all '''functions''' in '''Weather.pm''' with “'''use Weather'''” statement in this file.

So, no need to refer the '''functions''' within a package using the '''colon colon (::)package qualifier'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now let's see the next option.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| If option 2 is typed, it will prompt the user to enter the day of a week.

'''$dayoption''' is passed as the input parameter to the '''function write underscore daily underscore report.'''

'''return '''value from the '''function''' is stored in the variable '''dollar result'''.

'''Print statement''' asks the user to check the text file for the output.

The filename is created with the day of the week dot txt as output file.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| If option 3 is typed, it prints the weather report for the whole week.

'''Display underscore weekly underscore report''' is the '''function''' name of the weekly report.

This print statement draws a horizontal line for the specified number of times.

This is just to give a good look to the report.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Lastly, if the option is 4, it will quit the program.

If any option, other than the ones specified is given, the''' print statement''' says “'''Incorrect option'''”.

Here the exit value of 0 indicates the program ran successfully.

The exit value other than 0 means an error of some kind has occurred.

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| On the terminal type

'''perl weather_report. Pl'''

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to the '''terminal '''and type

'''perl weather underscore report dot pl'''
and press''' Enter'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| 1.Daily Weather Report

2.Daily Weather Report to File

3.Weekly Weather Report

4.Exit

Enter the Option: 1

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| We can see four options on the screen.

Type '''1 '''and press '''Enter.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Enter a day: monday

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| We are prompted to enter a day of the week.

I'll type ''''monday'''' and press '''Enter'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight the header of the report
| style="border:1pt solid #000000;padding:0.097cm;"| This is the header output generated from the '''function display underscore header().'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight the monday report
| style="border:1pt solid #000000;padding:0.097cm;"| Now, we can see the weather report of Monday.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now I'll again execute the program once again to demonstrate the other options.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| On the terminal type

'''perl weather_report. Pl'''

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"|

|-
| style="border:1pt solid #000000;padding:0.097cm;"| 1.Daily Weather Report

2.Daily Weather Report to File

3.Weekly Weather Report

4.Exit

Enter the Option: 2

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| Type '''2 '''and press '''Enter.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Enter a day: wednesday

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt, we have to type any week day.

I will type ‘'''wednesday’''' and press '''Enter'''.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| We can see a message “Please check the file wednesday dot txt for report output ”.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| The output has been written to this text file.

Let us open the file and check the content.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| On the terminal type

'''gedit wednesday.txt'''

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| Type '''gedit wednesday dot txt''' and press''' Enter.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight the output
| style="border:1pt solid #000000;padding:0.097cm;"| The output file has been created with the entered week day name with '''txt''' extension.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| Now let us check the next option.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| On the terminal type

'''perl weather_report. Pl'''

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| Switch to the terminal and type''' perl weather underscore report dot pl '''and press''' Enter'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| 1.Daily Weather Report

2.Daily Weather Report to File

3.Weekly Weather Report

4.Exit

Enter the Option: 3

'''>>'''press''' Enter.'''
| style="border:1pt solid #000000;padding:0.097cm;"| Type '''3 '''and press '''Enter.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Highlight the output
| style="border:1pt solid #000000;padding:0.097cm;"| This time, we can see the weekly weather report.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| The''' hash keys''' and''' hash values''' are stored in a random order.

So the displayed output is not related to the order in which they were added.

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.106cm;"| With this, we come to the end of this tutorial.

Let us summarize.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 6:
| style="border:1pt solid #000000;padding:0.106cm;"| In this tutorial we have seen a sample '''Perl''' program by covering main topics of our previous tutorials.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Slide 7:

Assignment
| style="border:1pt solid #000000;padding:0.106cm;"| As an assignment,

# Write a similar '''Perl''' program '''employee underscore report.pl''' for displaying employee salary, designation, department, leave_balance details.
# Pass Employee ID or Employee name as input.
# Write the required functions in the module '''Employee.pm '''file.

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

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 9:

Spoken Tutorial workshops

| style="border:1pt solid #000000;padding:0.106cm;"| We conduct workshops and give certificates for those who pass our online tests.

For more details, please write to us.

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

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.

|}

@@ Line 87: / Line 87: @@
 | style="border:1pt solid #000000;padding:0.097cm;"| Here I have used''' references''' to create complex data structures to hold the data required for a weather report.
-'''$weather_report''' is a''' hash reference''' with 5 keys.
+'''$weather_report''' is a''' hash reference'''.
 “'''place'''” and “'''nstate'''” has the scalar values.

PERL/C3/Sample-PERL-program/English - Revision history

Nancyvarkey at 11:35, 9 November 2015

Nirmala Venkat at 12:02, 5 November 2015

Nirmala Venkat: Created page with "'''Title of script''':''' Sample PERL Program''' '''Author: Nirmala Venkat''' '''Keywords: module, package, array, hash, functions, reference, dereference, PERL, PERL progra..."