Difference between revisions of "PERL/C3/Including-files-or-modules/English-timed"

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|-
 
|-
 
|00:01
 
|00:01
−
|Welcome to the''' Spoken Tutorial''' on''' Including files or modules in a PERL program'''
+
|Welcome to the''' Spoken Tutorial''' on''' Including files or modules''' in a '''PERL''' program.
  
 
|-
 
|-
 
|00:08
 
|00:08
−
|In this tutorial we will learn to use
+
|In this tutorial, we will learn to use:
−
* '''do'''
+
'''do'''
−
* '''use '''and
+
'''use '''and
−
* '''require'''
+
'''require'''
−
methods in''' PERL''' programming.
+
'''method'''s in PERL programming.
  
 
|-
 
|-
 
|00:16
 
|00:16
−
|For this tutorial, I am using
+
|For this tutorial, I am using:
−
* '''Ubuntu Linux 12.04''' operating system
+
'''Ubuntu Linux 12.04''' operating system
−
* '''Perl 5.14.2 and'''
+
'''Perl 5.14.2''' and
−
* '''gedit''' Text Editor
+
'''gedit''' Text Editor.
  
 
|-
 
|-
 
|00:28
 
|00:28
−
|You can use any text editor of your choice.
+
|You can use any '''text editor''' of your choice.
  
 
|-
 
|-
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|-
 
|-
 
|00:44
 
|00:44
−
|Do Method: These are simple ways to include the source code from other files into the current script file.
+
|''''do()' method''': These are simple ways to include the source code from other files into the current script file.
  
 
|-
 
|-
 
|00:53
 
|00:53
−
|Let us understand how to use '''do()''' method.
+
|Let us understand how to use '''do() method'''.
  
 
|-
 
|-
 
|00:57
 
|00:57
−
|Open a new file in your text editor and name it as '''datetime.pl'''  
+
|Open a new file in your text editor and name it as '''datetime dot pl'''.
  
 
|-
 
|-
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|-
 
|-
 
|01:09
 
|01:09
−
|From here onwards, remember to press the '''Enter key '''after every command on the '''terminal'''.
+
|From here onwards, remember to press the '''Enter''' key after every command on the '''terminal'''.
  
 
|-
 
|-
Line 60: Line 60:
 
|-
 
|-
 
|01:18
 
|01:18
−
|The current date and time is stored in a variable''' dollar datestring.'''
+
|The current date and time are stored in a variable''' dollar datestring.'''
  
 
|-
 
|-
 
|01:23
 
|01:23
−
|Here, I have a''' function''' by name''' msgThanks,''' which returns a “'''Thank you'''” message.
+
|Here, I have a function by name "msgThanks" which returns a “Thank you” message.
  
 
|-
 
|-
 
|01:31
 
|01:31
−
|Now, press''' Ctrl+S''' to save the file.
+
|Now, press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|01:35
 
|01:35
−
|Next let us look at another '''Perl '''program which will make use of this file''' datetime dot pl'''
+
|Next, let us look at another '''Perl '''program which will make use of this file''' datetime dot pl'''.
  
 
|-
 
|-
 
|01:43
 
|01:43
−
|Open a new file in your text editor and name it as '''main dot pl'''  
+
|Open a new file in your '''text editor''' and name it as '''main dot pl'''.
  
 
|-
 
|-
Line 92: Line 92:
 
|-
 
|-
 
|02:03
 
|02:03
−
|'''do()''' method is called with the filename from where we want to use the code.
+
|'do()' method is called with the filename from where we want to use the code.
  
 
|-
 
|-
 
|02:09
 
|02:09
−
|Current date and time is stored in the''' $datestring''' variable of''' datetime dot pl file.'''
+
|Current date and time are stored in the''' $datestring''' variable of''' datetime dot pl file.'''
  
 
|-
 
|-
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|-
 
|-
 
|02:21
 
|02:21
−
|Now, press''' Ctrl+S''' to save the file.
+
|Now, press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|02:25
 
|02:25
−
|Let us execute the program.
+
|Let us '''execute''' the program.
  
 
|-
 
|-
 
|02:27
 
|02:27
−
|Switch back to the''' terminal''' and type '''perl main dot pl '''and press''' Enter'''
+
|Switch back to the''' terminal''' and type: '''perl main dot pl '''and press''' Enter'''.
  
 
|-
 
|-
 
|02:34
 
|02:34
−
|Observe the output on the '''terminal.'''
+
|Observe the output on the terminal.
  
 
|-
 
|-
 
|02:37
 
|02:37
−
|Next we will learn how to use''' require method''' and''' use method''' in a '''Perl''' program.
+
|Next, we will learn how to use''' require()''' method and''' use()''' method in a '''Perl''' program.
  
 
|-
 
|-
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|-
 
|-
 
|02:52
 
|02:52
−
| '''use''' method is used only for the '''modules'''.
+
| '''use() method''' is used only for the '''modules'''.
  
 
|-
 
|-
 
|02:56
 
|02:56
−
| It is verified at the time of '''compilation'''
+
| It is verified at the time of '''compilation'''.
  
 
|-
 
|-
 
|02:59
 
|02:59
−
|There is no need to give the '''file extension'''
+
|There is no need to give the file '''extension'''.
  
 
|-
 
|-
 
| 03:03
 
| 03:03
−
|  '''require '''method is used for both '''Perl''' '''programs '''and '''modules'''
+
|  '''require()''' method is used for both Perl programs and '''modules'''.
  
 
|-
 
|-
 
|03:08
 
|03:08
−
| It is verified at the '''run time'''
+
| It is verified at the '''run''' time.
  
 
|-
 
|-
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|-
 
|-
 
|03:14
 
|03:14
−
| The syntax of '''use method '''is '''use module name semicolon'''
+
| The syntax of '''use''' method is: '''use module name semicolon'''.
  
 
|-
 
|-
 
|03:20
 
|03:20
−
| '''Perl modules''' are the files which end with '''.pm''' extension.
+
| '''Perl modules''' are the files which end with '.pm' extension.
  
 
|-
 
|-
 
|03:25
 
|03:25
−
| Reusability of code is implemented through '''modules'''.
+
| Re-usability of code is implemented through '''modules'''.
  
 
|-
 
|-
 
|03:30
 
|03:30
−
| These are similar to libraries in other languages.
+
| These are similar to '''libraries''' in other (computer) languages.
  
 
|-
 
|-
 
|03:35
 
|03:35
−
|Now I will show a simple program with the''' use method''' to include a''' module''' in '''Perl''' code.
+
|Now, I will show a simple program with the''' use method''' to include a module in Perl code.
  
 
|-
 
|-
 
|03:43
 
|03:43
−
|Open a new file In your '''text editor '''and name it as '''sum dot pm.'''  
+
|Open a new file in your '''text editor '''and name it as '''sum dot pm.'''  
  
 
|-
 
|-
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|-
 
|-
 
|04:01
 
|04:01
−
|Now, press''' Ctrl+S''' to save the file
+
|Now, press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|04:05
 
|04:05
−
|We will write another '''Perl''' script where we’ll use this''' sum.pm''' file.
+
|We will write another '''Perl script''' where we’ll use this''' sum dot pm''' file.
  
 
|-
 
|-
 
| 04:11
 
| 04:11
−
| Let me open the sample program app dot pl file which I have saved already
+
| Let me open the sample program '''app dot pl''' file which I have saved already.
  
 
|-
 
|-
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|-
 
|-
 
|04:25
 
|04:25
−
|The first line shows the use method with the '''module '''name.
+
|The first line shows the '''use''' method with the module name.
  
 
|-
 
|-
 
|04:29
 
|04:29
−
|In our case, the '''module '''name is '''sum'''.
+
|In our case, the module name is 'sum'.
  
 
|-
 
|-
 
|04:33
 
|04:33
−
|We are passing 1,7,5,4,9 as '''input parameters '''to the function '''total''' in '''sum dot pm '''file.
+
|We are passing 1, 7, 5, 4, 9 as '''input parameters '''to the function '''total()''' in '''sum dot pm '''file.
  
 
|-
 
|-
 
|04:44
 
|04:44
−
|Again, in the next line, we are passing 1 to 10 as '''input parameters '''to the same '''function'''.
+
|Again, in the next line, we are passing 1 to 10 as '''input parameters '''to the same function.
  
 
|-
 
|-
 
|04:52
 
|04:52
−
|Now, press''' Ctrl+S''' to save the file.
+
|Now, press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|04:56
 
|04:56
−
|Let us execute the program.
+
|Let us '''execute''' the program.
  
 
|-
 
|-
 
|04:59
 
|04:59
−
|Switch back to the''' terminal''' and type '''perl app dot pl''' and Press '''Enter'''
+
|Switch back to the terminal and type: '''perl app dot pl''' and press '''Enter'''.
  
 
|-
 
|-
 
|05:06
 
|05:06
−
|Observe the output displayed on the '''terminal.'''
+
|Observe the output displayed on the terminal.
  
 
|-
 
|-
 
|05:10
 
|05:10
−
|Let us see few more options in''' use method'''. Switch back to''' sum.pm '''in the '''text editor.'''
+
|Let us see few more options in''' use method'''. Switch back to''' sum dot pm '''in the '''text editor.'''
  
 
|-
 
|-
 
|05:18
 
|05:18
−
|At the beginning of the source code, add the lines  '''use strict semicolon''' '''use warnings semicolon'''
+
|At the beginning of the source code, add the lines  "use strict" semicolon, "use warnings" semicolon.
  
 
|-
 
|-
 
|05:27
 
|05:27
−
|'''use strict''' and''' use warnings''' are '''compiler flags '''that instruct''' Perl''' to behave in a stricter way.
+
|"use strict" and "use warnings" are '''compiler flags '''that instruct Perl to behave in a stricter way.
  
 
|-
 
|-
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|-
 
|-
 
|05:39
 
|05:39
−
|'''use strict''' forces the user to declare all the '''variables''' used in the program.
+
|'''use strict''' forces the user to declare all the variables used in the program.
  
 
|-
 
|-
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|-
 
|-
 
|05:56
 
|05:56
−
|Assume that we forgot to declare the '''variable $sum '''as''' my'''.
+
|Assume that we forgot to declare the variable '''$sum '''as''' my'''.
  
 
|-
 
|-
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|-
 
|-
 
|06:06
 
|06:06
−
|Press''' Ctrl+S''' to save the file.
+
|Press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|06:09
 
|06:09
−
|Switch back to the''' terminal''' and type '''perl app dot pl'''
+
|Switch back to the terminal and type: '''perl app dot pl'''.
  
 
|-
 
|-
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|-
 
|-
 
|06:21
 
|06:21
−
|The first set of lines displayed on the '''terminal''' are '''error messages''' generated by “'''use strict'''”.
+
|The first set of lines displayed on the terminal are '''error messages''' generated by “use strict”.
  
 
|-
 
|-
 
|06:29
 
|06:29
−
|The last two are the abort messages.
+
|The last two are the '''abort''' messages.
  
 
|-
 
|-
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|-
 
|-
 
|06:36
 
|06:36
−
|Next let us see a '''Perl program '''where we use the''' require''' method.
+
|Next, let us see a Perl program where we use the''' require''' method.
  
 
|-
 
|-
 
|06:41
 
|06:41
−
|Let me open the sample program''' commonfunctions.pl''' which I have already saved.
+
|Let me open the sample program''' commonfunctions dot pl''' which I have already saved.
  
 
|-
 
|-
 
|06:48
 
|06:48
−
|Type the following code as displayed on the screen in your '''commonfunctions dot pl''' file.
+
|Type the following code as displayed on the screen in your '''commonfunctions dot pl''' file. Let us understand the code now.
−
Let us understand the code now.
+
  
 
|-
 
|-
 
|06:57
 
|06:57
−
|Here we can see a collection of commonly used '''functions'''.
+
|Here, we can see a collection of commonly used functions.
  
 
|-
 
|-
 
|07:01
 
|07:01
−
|The first '''function square()''' returns the square of a number.
+
|The first function, '''square()''', returns the square of a number.
  
 
|-
 
|-
 
|07:06
 
|07:06
−
|The second '''function square underscore root()''' returns the square root of a given number.
+
|The second function, '''square underscore root()''', returns the square root of a given number.
  
 
|-
 
|-
 
|07:12
 
|07:12
−
|Next '''function random underscore number()''' generates a random number.
+
|Next function, '''random underscore number()''', generates a random number.
  
 
|-
 
|-
 
|07:18
 
|07:18
−
|The last '''function random underscore range()''' generates a random number between a lower range and upper range of numbers.
+
|The last function '''random underscore range()''', generates a random number between a lower range and upper range of numbers.
  
 
|-
 
|-
 
|07:26
 
|07:26
−
|Note that we need the '''1 semicolon''' at the end of the file.
+
|Note that we need the '''1 semicolon''' (1;) at the end of the file.
  
 
|-
 
|-
 
|07:31
 
|07:31
−
|This is because''' Perl''' needs the last expression in the file to return a '''true value'''.
+
|This is because''' Perl''' needs the last expression in the file to return a '''true''' value.
  
 
|-
 
|-
 
|07:37
 
|07:37
−
|Now, press''' Ctrl+S''' to save the file.
+
|Now, press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|07:41
 
|07:41
−
|Next we will write a''' Perl''' program in which we’ll call these '''subroutines '''using''' require''' method.
+
|Next, we will write a Perl program in which we’ll '''call''' these '''subroutines '''using "require" method.
  
 
|-
 
|-
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|-
 
|-
 
|08:02
 
|08:02
−
|'''require''' reads the''' commonfunctions.pl''' file containing '''Perl''' code and compiles it.
+
|'''require''' reads the''' commonfunctions dot pl''' file, containing Perl code, and compiles it.
  
 
|-
 
|-
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|-
 
|-
 
|08:17
 
|08:17
−
|One is to find the square of a number.
+
|1: (one) is to find the square of a number.
  
 
|-
 
|-
 
|08:20
 
|08:20
−
|Two is for square root of a number.
+
|2: Two is for square root of a number.
  
 
|-
 
|-
 
|08:23
 
|08:23
−
|Three is for a random number in the given range. Four is to quit the program.
+
|3: Three is for a random number in the given range. 4: Four is to quit the program.
  
 
|-
 
|-
 
|08:29
 
|08:29
−
|If option one is typed, it will ask the user to enter a number.
+
|If option 1 (one) is typed, it will ask the user to enter a number.
  
 
|-
 
|-
 
|08:34
 
|08:34
−
|The value is stored in''' $number.''' This is passed to the function''' square''' in''' commonfunctions.pl''' file.
+
|The value is stored in''' $number.''' The value is passed to the function '''square()''' in''' commonfunctions dot pl''' file.
  
 
|-
 
|-
Line 384: Line 383:
  
 
|-
 
|-
−
|08:47'
+
|08:47
−
|The '''print statement''' prints the square of a number as output.
+
|The '''print''' statement prints the square of a number as output.
  
 
|-
 
|-
 
|08:52
 
|08:52
−
|If option two is typed, the square root of a number is displayed as output.
+
|If option 2 (two) is typed, the square root of a number is displayed as output.
  
 
|-
 
|-
 
|08:58
 
|08:58
−
|The execution is followed as explained in the previous '''function square'''.
+
|The execution is followed as explained in the previous function '''square()'''.
  
 
|-
 
|-
 
|09:03
 
|09:03
−
|If option three is typed, a random number is displayed as output in the given range.
+
|If option 3 (three) is typed, a random number is displayed as output in the given range.
  
 
|-
 
|-
 
|09:09
 
|09:09
−
|Else if option is four, the program exits. If any option other than the ones specified is given, the '''print statement '''says “Incorrect option”.
+
|Else, if option is 4 (four), the program exits. If any option other than the ones specified is given, the '''print''' statement says “Incorrect option”.
  
 
|-
 
|-
 
|09:20
 
|09:20
−
|Note that in this program we have called only three functions out of four from '''commonfunctions.pl'''.
+
|Note that in this program, we have called only three functions out of four from '''commonfunctions dot pl'''.
 
|-
 
|-
 
|09:28
 
|09:28
−
|Now, press''' Ctrl+S''' to save the file
+
|Now, press''' Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
 
|09:31
 
|09:31
−
|Let us execute the program.
+
|Let us '''execute''' the program.
  
 
|-
 
|-
 
|09:34
 
|09:34
−
|Switch back to the''' terminal''' and type '''perl callprogram dot pl'''
+
|Switch back to the terminal and type: '''perl callprogram dot pl'''.
  
 
|-
 
|-
 
|09:41
 
|09:41
−
|Observe the output
+
|Observe the output.
  
 
|-
 
|-
Line 428: Line 427:
 
|-
 
|-
 
|09:49
 
|09:49
−
|Type''' perl callprogram dot pl'''
+
|Type:''' perl callprogram dot pl'''.
  
 
|-
 
|-
 
|09:53
 
|09:53
−
|Now, '''Enter the Option''' as 3.
+
|Now, enter the option as 3.
  
 
|-
 
|-
Line 452: Line 451:
 
|-
 
|-
 
|10:11
 
|10:11
−
|This brings us to the end of this tutorial. Let us summarise.
+
|This brings us to the end of this tutorial. Let us summarize.
  
 
|-
 
|-
 
|10:16
 
|10:16
−
|In this tutorial we learnt to use
+
|In this tutorial, we learnt to use:
−
* '''do'''
+
'''do'''
−
* '''use'''
+
'''use'''
−
* '''require methods '''in''' PERL''' programming.
+
'''require methods '''in PERL programming.
  
 
|-
 
|-
 
|10:24
 
|10:24
−
|'''Note''': "'''use Module'''" is recommended over "'''require Module'''", because it determines '''module availability '''at '''compile time'''.
+
|Note: "use" '''module''' is recommended over "require" module, because it determines module availability at '''compile time'''.
 
|-
 
|-
 
|10:33
 
|10:33
−
|Here is an assignment for you.
+
|Here is an assignment for you. Write a Perl program''' reminder.pl''' where you will write a letter to the participants.
−
Write a''' Perl''' program''' reminder.pl''' where you will write a letter to the participants.
+
  
 
|-
 
|-
 
|10:41
 
|10:41
−
|Prompt the user to enter''' To''' and''' From''' name
+
|Prompt the user to enter''' To''' and''' From''' name.
  
 
|-
 
|-
 
|10:45
 
|10:45
−
|Call the subroutines from''' Letter.pm''' using '''‘use’''' method.
+
|'''Call''' the subroutines from''' Letter dot pm''' using ‘use’ method.
  
 
|-
 
|-
 
|10:50
 
|10:50
−
| Write the below functions in''' Letter.pm '''file.
+
| Write the below functions in''' Letter dot pm '''file.
  
 
|-
 
|-
 
|10:54
 
|10:54
−
| LetterDate() function returns the current date and time
+
| '''LetterDate()''' function returns the current date and time.
  
 
|-
 
|-
 
|10:58
 
|10:58
−
|To() function returns the name of the participants
+
|'''To()''' function returns the names of the participants.
  
 
|-
 
|-
 
|11:02
 
|11:02
−
| From() function returns the sender name
+
| '''From()''' function returns the sender's name.
  
 
|-
 
|-
 
|11:05
 
|11:05
−
| Lettermsg() function returns the content of the letter
+
|''' Lettermsg()''' function returns the contents of the letter.
  
 
|-
 
|-
 
|11:09
 
|11:09
−
|Thanksmsg() function returns thanks and regards.
+
|'''Thanksmsg()''' function returns "thanks" and "regards".
  
 
|-
 
|-
Line 507: Line 505:
 
|-
 
|-
 
| 11:20
 
| 11:20
−
|The video at the following link summarize the spoken tutotial project. Please download and watch it
+
|The video at the following link summarizes the spoken tutotial project. Please download and watch it.
  
 
|-
 
|-
 
|11:27
 
|11:27
−
|The''' Spoken Tutorial Project''' Team
+
|The''' Spoken Tutorial Project''' team:
−
 
+
conducts workshops using spoken tutorials and
−
* conducts workshops using spoken tutorials and
+
gives certificates on passing online tests.
−
* gives certificates on passing online tests.
+
  
 
|-
 
|-
Line 523: Line 520:
 
|11:40
 
|11:40
 
|Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.
 
|Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.
−
 
 
More information on this mission is available at this link.
 
More information on this mission is available at this link.
  
 
|-
 
|-
 
|11:51
 
|11:51
−
|This is Nirmala Venkat from IIT Bombay, signing off. Thanks for watching.
+
|This is Nirmala Venkat from '''IIT Bombay''', signing off. Thanks for watching.
  
 
|}
 
|}

Latest revision as of 18:23, 20 February 2017

Time Narration
00:01 Welcome to the Spoken Tutorial on Including files or modules in a PERL program.
00:08 In this tutorial, we will learn to use:

do use and require methods in PERL programming.

00:16 For 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.
00:44 'do()' method: These are simple ways to include the source code from other files into the current script file.
00:53 Let us understand how to use do() method.
00:57 Open a new file in your text editor and name it as datetime dot pl.
01:03 In the datetime dot pl file, type the following code as displayed on the screen.
01:09 From here onwards, remember to press the Enter key after every command on the terminal.
01:15 Let us understand the code now.
01:18 The current date and time are stored in a variable dollar datestring.
01:23 Here, I have a function by name "msgThanks" which returns a “Thank you” message.
01:31 Now, press Ctrl+S to save the file.
01:35 Next, let us look at another Perl program which will make use of this file datetime dot pl.
01:43 Open a new file in your text editor and name it as main dot pl.
01:49 In the main dot pl file, type the following code as displayed on the screen.
01:55 Let me explain the code now.
01:58 Here, the first line prints the welcome message.
02:03 'do()' method is called with the filename from where we want to use the code.
02:09 Current date and time are stored in the $datestring variable of datetime dot pl file.
02:16 And at the end, we call the msgThanks() function from the same file.
02:21 Now, press Ctrl+S to save the file.
02:25 Let us execute the program.
02:27 Switch back to the terminal and type: perl main dot pl and press Enter.
02:34 Observe the output on the terminal.
02:37 Next, we will learn how to use require() method and use() method in a Perl program.
02:44 These methods are used - when we have collections of subroutines that can be used in multiple Perl programs.
02:52 use() method is used only for the modules.
02:56 It is verified at the time of compilation.
02:59 There is no need to give the file extension.
03:03 require() method is used for both Perl programs and modules.
03:08 It is verified at the run time.
03:10 One needs to give the file extension.
03:14 The syntax of use method is: use module name semicolon.
03:20 Perl modules are the files which end with '.pm' extension.
03:25 Re-usability of code is implemented through modules.
03:30 These are similar to libraries in other (computer) languages.
03:35 Now, I will show a simple program with the use method to include a module in Perl code.
03:43 Open a new file in your text editor and name it as sum dot pm.
03:49 In the sum dot pm file, type the following code as displayed on the screen.
03:55 Here, I have a simple function which will calculate the sum of a given set of numbers.
04:01 Now, press Ctrl+S to save the file.
04:05 We will write another Perl script where we’ll use this sum dot pm file.
04:11 Let me open the sample program app dot pl file which I have saved already.
04:17 In the app dot pl file, type the following code as displayed on the screen.
04:22 Let me explain the code now.
04:25 The first line shows the use method with the module name.
04:29 In our case, the module name is 'sum'.
04:33 We are passing 1, 7, 5, 4, 9 as input parameters to the function total() in sum dot pm file.
04:44 Again, in the next line, we are passing 1 to 10 as input parameters to the same function.
04:52 Now, press Ctrl+S to save the file.
04:56 Let us execute the program.
04:59 Switch back to the terminal and type: perl app dot pl and press Enter.
05:06 Observe the output displayed on the terminal.
05:10 Let us see few more options in use method. Switch back to sum dot pm in the text editor.
05:18 At the beginning of the source code, add the lines "use strict" semicolon, "use warnings" semicolon.
05:27 "use strict" and "use warnings" are compiler flags that instruct Perl to behave in a stricter way.
05:35 These are used to avoid common programming mistakes.
05:39 use strict forces the user to declare all the variables used in the program.
05:45 If there are errors, use strict will abort the execution.
05:50 use warnings will only provide warnings but continue with the execution.
05:56 Assume that we forgot to declare the variable $sum as my.
06:02 Let us now see how the same program is executed.
06:06 Press Ctrl+S to save the file.
06:09 Switch back to the terminal and type: perl app dot pl.
06:15 We can see that the program is aborted without executing the result.
06:21 The first set of lines displayed on the terminal are error messages generated by “use strict”.
06:29 The last two are the abort messages.
06:32 So, this is how the use method options work.
06:36 Next, let us see a Perl program where we use the require method.
06:41 Let me open the sample program commonfunctions dot pl which I have already saved.
06:48 Type the following code as displayed on the screen in your commonfunctions dot pl file. Let us understand the code now.
06:57 Here, we can see a collection of commonly used functions.
07:01 The first function, square(), returns the square of a number.
07:06 The second function, square underscore root(), returns the square root of a given number.
07:12 Next function, random underscore number(), generates a random number.
07:18 The last function random underscore range(), generates a random number between a lower range and upper range of numbers.
07:26 Note that we need the 1 semicolon (1;) at the end of the file.
07:31 This is because Perl needs the last expression in the file to return a true value.
07:37 Now, press Ctrl+S to save the file.
07:41 Next, we will write a Perl program in which we’ll call these subroutines using "require" method.
07:48 Let me open the sample program callprogram dot pl which I have already saved.
07:54 Type the following code as displayed on the screen in your file. Let me explain the code now.
08:02 require reads the commonfunctions dot pl file, containing Perl code, and compiles it.
08:09 This program gives 4 options to the user. The user has to choose one option at a time.
08:17 1: (one) is to find the square of a number.
08:20 2: Two is for square root of a number.
08:23 3: Three is for a random number in the given range. 4: Four is to quit the program.
08:29 If option 1 (one) is typed, it will ask the user to enter a number.
08:34 The value is stored in $number. The value is passed to the function square() in commonfunctions dot pl file.
08:44 The function returns the square of a number.
08:47 The print statement prints the square of a number as output.
08:52 If option 2 (two) is typed, the square root of a number is displayed as output.
08:58 The execution is followed as explained in the previous function square().
09:03 If option 3 (three) is typed, a random number is displayed as output in the given range.
09:09 Else, if option is 4 (four), the program exits. If any option other than the ones specified is given, the print statement says “Incorrect option”.
09:20 Note that in this program, we have called only three functions out of four from commonfunctions dot pl.
09:28 Now, press Ctrl+S to save the file.
09:31 Let us execute the program.
09:34 Switch back to the terminal and type: perl callprogram dot pl.
09:41 Observe the output.
09:44 I'll execute the program once again with a different option.
09:49 Type: perl callprogram dot pl.
09:53 Now, enter the option as 3.
09:56 Enter a lower range as 50.
09:59 Enter a upper range as 99.
10:02 We can see the random number is generated in the given range of numbers.
10:08 Try other options on your own.
10:11 This brings us to the end of this tutorial. Let us summarize.
10:16 In this tutorial, we learnt to use:

do use require methods in PERL programming.

10:24 Note: "use" module is recommended over "require" module, because it determines module availability at compile time.
10:33 Here is an assignment for you. Write a Perl program reminder.pl where you will write a letter to the participants.
10:41 Prompt the user to enter To and From name.
10:45 Call the subroutines from Letter dot pm using ‘use’ method.
10:50 Write the below functions in Letter dot pm file.
10:54 LetterDate() function returns the current date and time.
10:58 To() function returns the names of the participants.
11:02 From() function returns the sender's name.
11:05 Lettermsg() function returns the contents of the letter.
11:09 Thanksmsg() function returns "thanks" and "regards".
11:13 The output should be displayed as shown here.
11:20 The video at the following link summarizes the spoken tutotial project. Please download and watch it.
11:27 The Spoken Tutorial Project team:

conducts workshops using spoken tutorials and gives certificates on passing online tests.

11:36 For more details, please write to us.
11:40 Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.

11:51 This is Nirmala Venkat from IIT Bombay, signing off. Thanks for watching.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14

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