Difference between revisions of "PERL/C2/More-Conditional-statements/English-timed"

From Script | Spoken-Tutorial
Jump to: navigation, search
 
(9 intermediate revisions by 3 users not shown)
Line 1: Line 1:
 
{| border=1
 
{| border=1
−
!  <center>'''Visual Cue'''</center>
+
|'''Time'''
−
!  <center>'''Narration'''</center>
+
|'''Narration'''
 
   
 
   
 
|-
 
|-
−
| 00.00
+
| 00:00
−
|Welcome to the spoken tutorial on ''' if-elsif-else ''' and '''switch''' conditional statements in Perl.
+
|Welcome to the spoken tutorial on ''' if-elsif-else ''' and '''switch''' '''conditional statements''' in '''PERL'''.
 
   
 
   
 
|-
 
|-
−
| 00.07
+
| 00:07
−
| In this tutorial, we will learn about  
+
|In this tutorial, we will learn about  
  
 
|-
 
|-
−
|00.10
+
|00:10
−
|The ''' if-elsif-else''' statement and ''' switch''' statement in '''Perl '''
+
|the '''if-elsif-else''' statement and ''' switch''' statement in '''Perl '''.
 
   
 
   
 
|-
 
|-
−
|00.15
+
|00:15
−
| I am using '''Ubuntu Linux12.04''' operating system and '''Perl 5.14.2'''
+
| I am using '''Ubuntu Linux 12.04''' operating system and '''Perl 5.14.2'''.
−
+
 
   
 
   
 
|-
 
|-
−
|00.22
+
|00:22
 
|I will also be using the '''gedit '''Text Editor.
 
|I will also be using the '''gedit '''Text Editor.
−
 
 
   
 
   
 
|-
 
|-
−
|00.25
+
|00:25
 
|You can use any text editor of your choice.
 
|You can use any text editor of your choice.
 
   
 
   
 
|-
 
|-
−
| 00.29
+
| 00:29
−
| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''
+
| You should have basic knowledge of variables and '''comments '''in''' Perl'''
 
   
 
   
 
|-
 
|-
−
| 00.34
+
| 00:34
 
|and knowledge of ''' for, foreach, while''' and '''do-while''' loops and  
 
|and knowledge of ''' for, foreach, while''' and '''do-while''' loops and  
  
 
|-
 
|-
−
| 00.38
+
| 00:38
−
| ''' if ''' and '''if-else''' statements will be an added advantage.
+
| ''' if''' and '''if-else''' statements will be an added advantage.
  
 
|-
 
|-
−
|00.43
+
|00:43
−
|Please go through the relevant spoken tutorials on the '''spoken tutorial '''website.
+
|Please go through the relevant spoken tutorials on the '''Spoken Tutorial '''website.
 
   
 
   
 
|-
 
|-
−
|00.48
+
|00:48
 
|''' If-elsif-else''' statement in '''Perl''' can be used  
 
|''' If-elsif-else''' statement in '''Perl''' can be used  
 
   
 
   
 
|-
 
|-
−
| 00.52
+
| 00:52
 
| to test multiple conditions and  
 
| to test multiple conditions and  
 
   
 
   
 
|-
 
|-
−
|00.54
+
|00:54
−
|When all conditions fail then it executes the default '''else''' block  
+
|when all conditions fail then it executes the default '''else''' block.
 
   
 
   
 
|-
 
|-
−
|00.59
+
|00:59
−
|The syntax of '''if-elsif-else''' statement is as follows  
+
|The syntax of '''if-elsif-else''' statement is as follows.
 
   
 
   
 
|-
 
|-
−
|01.04
+
|01:04
−
|''' if space''' open bracket ''' condition''' close bracket space Open curly bracket press Enter
+
|''' if''' space open bracket ''' condition1''' close bracket space open curly bracket press '''Enter'''
 
   
 
   
 
|-
 
|-
−
|01.13
+
|01:13
−
|piece of code  to be executed when the condition is true semicolon
+
|piece of code  to be executed when the condition is '''true''' semicolon
 
   
 
   
−
 
 
|-
 
|-
−
|01.18
+
|01:18
−
|Press '''Enter '''
+
|press '''Enter '''.
  
 
|-
 
|-
−
| 01.20
+
| 01:20
−
| Close curly bracket space '''elsif''' space open bracket ''' condition''' close bracket space open curly bracket  
+
| Close curly bracket space '''elsif''' space open bracket ''' condition2''' close bracket space open curly bracket  
  
 
|-
 
|-
−
|01.30
+
|01:30
−
|Press '''Enter '''
+
|press '''Enter ''', another piece of code semicolon  
−
 
+
−
|-
+
−
|01.31
+
−
|another piece of code semicolon  
+
 
   
 
   
 
|-
 
|-
−
|01.33
+
|01:33
−
|to be executed when '''elsif condition''' is true  
+
|to be executed when '''elsif condition''' is '''true'''
 
   
 
   
 
|-
 
|-
−
|01.37
+
|01:37
−
|Press '''Enter '''
+
|press '''Enter '''.
 
   
 
   
 
|-
 
|-
−
|01.39
+
|01:39
−
|close curly bracket space ''' else'''  space open curly bracket  
+
|Close curly bracket space''' else'''  space open curly bracket  
−
 
+
 
   
 
   
 
|-
 
|-
−
|01.44
+
|01:44
−
| Enter  
+
|'''Enter'''. Code to be executed when both the above conditions are '''false''' semicolon
−
+
−
|-
+
−
| 01.45
+
−
|code semicolon  to be executed when both the above conditions are false semicolon
+
  
 
|-
 
|-
−
|01.51
+
|01:51
−
|Press '''Enter '''
+
|press '''Enter '''.Close curly bracket.
−
+
−
|-
+
−
|01.52
+
−
| close curly bracket  
+
  
 
|-
 
|-
−
| 01.55
+
| 01:55
−
| First, the ''' if ''' condition is checked and executed if the condition is true.  
+
| First, the '''if''' condition is checked and executed if the '''condition1''' is '''true'''.  
 
   
 
   
 
|-
 
|-
−
|02.01
+
|02:01
−
|If not, then the ''' else if''' condition is checked and executed if it is true.  
+
|If not, then the ''' else if''' condition is checked and executed if it is '''true'''.  
 
   
 
   
 
|-
 
|-
−
|02.06     
+
|02:06     
 
|Otherwise, the code within '''else''' block is executed.  
 
|Otherwise, the code within '''else''' block is executed.  
 
   
 
   
 
|-
 
|-
−
|02.11
+
|02:11
 
|Now let us look at an example of '''if-elsif-else''' statement.  
 
|Now let us look at an example of '''if-elsif-else''' statement.  
 
   
 
   
 
|-
 
|-
−
|02.16
+
|02:16
−
|Open the Terminal and type  
+
|Open the Terminal and type:
 
   
 
   
 
|-
 
|-
−
|02.19
+
|02:19
 
| '''gedit conditionalBlocks dot pl space ampersand'''
 
| '''gedit conditionalBlocks dot pl space ampersand'''
−
+
 
−
+
 
|-
 
|-
−
|02.26
+
|02:26
−
| and press '''Enter'''
+
| and press '''Enter'''.
 
   
 
   
 
|-
 
|-
−
|02.28
+
|02:28
−
|This will open the ''' conditionalBlocks.pl''' file in '''gedit. '''
+
|This will open the " conditionalBlocks.pl" file in '''gedit. '''
 
   
 
   
 
|-
 
|-
−
|02.33
+
|02:33
 
|Type the following piece of code as displayed on the screen.  
 
|Type the following piece of code as displayed on the screen.  
 
   
 
   
 
|-
 
|-
−
| 02.38     
+
| 02:38     
−
| We have assigned the value ''' 'Perl' ''' to variable language.
+
| We have assigned the value 'Perl' to the variable '''language'''.
  
 
|-
 
|-
−
|02.44
+
|02:44
−
|Note that, '''eq''' is  '''string comparison''' operator.  
+
|Note that '''eq''' is  '''string comparison''' operator.  
 
   
 
   
 
|-
 
|-
−
|02.49
+
|02:49
−
| And then we have the various conditons that we want to check.
+
|And then we have various conditions that we want to check.
 
   
 
   
 
|-
 
|-
−
|02.55
+
|02:55
−
|Now, press ctrl+s to save the file.  
+
|Now, press '''Ctrl+s''' to '''save''' the file.  
−
+
 
−
+
 
|-
 
|-
−
|02.58
+
|02:58
 
|Then switch to terminal and execute file directly.  
 
|Then switch to terminal and execute file directly.  
 
   
 
   
 
|-
 
|-
−
| 03.02
+
| 03:02
−
| Type, '''perl conditionalBlocks dot pl '''
+
|Type: '''perl conditionalBlocks dot pl '''
−
 
+
 
   
 
   
 
|-
 
|-
−
|03.09
+
|03:09
 
|Note: I am skipping the compilation step. It is not a mandatory step for executing Perl scripts.  
 
|Note: I am skipping the compilation step. It is not a mandatory step for executing Perl scripts.  
 
   
 
   
 
|-
 
|-
−
| 03.16
+
|03:16
 
| If there is any compilation error,  
 
| If there is any compilation error,  
 
   
 
   
 
|-
 
|-
−
|   03.18
+
|03:18
−
| execution will throw an error and will stop execution of script
+
| execution will throw an error and will stop execution of script.
 
   
 
   
−
 
 
|-
 
|-
−
| 03.23
+
| 03:23
 
| Now press '''Enter.'''
 
| Now press '''Enter.'''
−
 
 
   
 
   
 
|-
 
|-
−
|03.25
+
|03:25
 
|The output shown on the terminal is  
 
|The output shown on the terminal is  
 
   
 
   
 
|-
 
|-
−
| 03.27
+
| 03:27
−
| ''' Hi, I am Perl '''
+
| "Hi, I am Perl"
 
   
 
   
 
|-
 
|-
−
| 03.29
+
| 03:29
 
| Now, let us look at our next case.  
 
| Now, let us look at our next case.  
 
   
 
   
 
|-
 
|-
−
|03.31
+
|03:31
 
|Switch to '''gedit. '''
 
|Switch to '''gedit. '''
 
   
 
   
 
|-
 
|-
−
|03.33  
+
|03:33  
−
|Assign ''' 'Java' ''' to variable language as shown.  
+
|Assign 'Java' to variable '''language''' as shown.  
 
   
 
   
 
|-
 
|-
−
| 03.37
+
|03:37
−
| Press '''ctrl+s''' to save the file.  
+
| Press '''Ctrl+s''' to '''save''' the file.  
 
   
 
   
 
|-
 
|-
−
|03.40
+
|03:40
 
|Switch to the terminal and execute the file.  
 
|Switch to the terminal and execute the file.  
−
 
 
   
 
   
 
|-
 
|-
−
|03.43
+
|03:43
−
|Type ''' perl conditionalBlocks dot pl '''
+
|Type: '''perl conditionalBlocks dot pl '''
−
 
+
 
   
 
   
 
|-
 
|-
−
|  03.50
+
|  03:50
 
| and press '''Enter.'''
 
| and press '''Enter.'''
 
   
 
   
 
|-
 
|-
−
|   03.53
+
|03:53
−
| The output shown on terminal is ''' Hi, I am Java '''
+
|The output shown on the terminal is "Hi, I am Java".
 
   
 
   
 
|-
 
|-
−
|  03.59
+
|  03:59
 
| Again let us switch back to '''gedit. '''
 
| Again let us switch back to '''gedit. '''
 
   
 
   
 
|-
 
|-
−
| 04.03
+
| 04:03
−
| Now, let us assign  ''' 'English' ''' to the ''' language''' variable.  
+
| Now, let us assign  'English' to the '''language''' variable.  
  
 
|-
 
|-
−
| 04.07
+
| 04:07
 
| Press ''' ctrl+s ''' to save the file.  
 
| Press ''' ctrl+s ''' to save the file.  
 
   
 
   
−
 
 
|-
 
|-
−
|04.09
+
|04:09
 
|Switch to the terminal and execute the file.  
 
|Switch to the terminal and execute the file.  
−
+
 
−
+
 
|-
 
|-
−
|04.13
+
|04:13
−
|Type '''perl conditionalBlocks dot pl '''
+
|Type: '''perl conditionalBlocks dot pl '''
−
 
+
 
   
 
   
 
|-
 
|-
−
|04.18
+
|04:18
−
|and press '''Enter.'''
+
|and press '''Enter.''' The output shown on the terminal is:
−
+
−
|-
+
−
|04.19
+
−
|The output shown on terminal is  
+
  
 
|-
 
|-
−
|04.22
+
|04:22
−
|'''I am not a computer language '''
+
|"I am not a computer language".
 
   
 
   
 
|-
 
|-
−
| 04.27
+
| 04:27
−
| The 3 cases imply that;
+
|The three cases imply that  
  
 
|-
 
|-
−
| 04.29
+
| 04:29
−
| Only one ''' if block''' that satisfies the condition will be executed.
+
| only one '''if block''' that satisfies the '''condition''' will be executed.
 
   
 
   
 
|-
 
|-
−
|04.35
+
|04:35
−
| otherwise the default ''' else block''' will get execute.  
+
| Otherwise the default '''else block''' will get executed.  
  
 
|-
 
|-
−
|04.39
+
|04:39
 
|We can have multiple ''' elsif''' conditions as per our requirement, like this.  
 
|We can have multiple ''' elsif''' conditions as per our requirement, like this.  
 
   
 
   
 
|-
 
|-
−
|04.46
+
|04:46
 
|Here is an assignment for you -  
 
|Here is an assignment for you -  
 
   
 
   
 
|-
 
|-
−
|04.48
+
|04:48
 
|Write an ''' if-elsif-else''' statement to print   
 
|Write an ''' if-elsif-else''' statement to print   
 
   
 
   
 
|-
 
|-
−
|04.51
+
|04:51
−
|''' “I am a Science graduate” ''' if '''stream''' is ''' science '''
+
| “I am a Science graduate” if '''stream''' is 'science'  
  
 
|-
 
|-
−
|04.55
+
|04:55
−
|'''“I am a Commerce graduate” ''' if '''stream''' is '''commerce'''  
+
|“I am a Commerce graduate” if '''stream''' is 'commerce'
−
+
 
−
+
 
|-
 
|-
−
|04.59
+
|04:59
−
|''' “I am an Arts graduate” ''' if ''' stream''' is neither ''' science''' or '''commerce '''
+
| “I am an Arts graduate” if ''' stream''' is neither 'science' nor 'commerce'.
−
+
 
   
 
   
 
|-
 
|-
−
|05.06
+
|05:06
 
|Now let us learn about the '''switch''' statement.  
 
|Now let us learn about the '''switch''' statement.  
−
 
 
   
 
   
 
|-
 
|-
−
| 05.10
+
|05:10
 
| Till Perl 5.8, there was no '''switch''' statement in '''Perl.'''  
 
| Till Perl 5.8, there was no '''switch''' statement in '''Perl.'''  
 
   
 
   
 
|-
 
|-
−
| 05.14
+
|05:14
−
| After that, '''Switch module''' was introduced,
+
| After that, '''Switch module''' was introduced  
 
   
 
   
 
|-
 
|-
−
|05.18
+
|05:18
 
|which provided the functionality of ''' switch''' statement.  
 
|which provided the functionality of ''' switch''' statement.  
 
   
 
   
 
|-
 
|-
−
|  05.22
+
|  05:22
−
| Note: ''' Modules''' in '''Perl''' will be covered in subsequent tutorials.  
+
| Note: '''Modules''' in '''Perl''' will be covered in subsequent tutorials.  
  
 
|-
 
|-
−
|  05.27
+
|  05:27
−
| The syntax of ''' switch''' is as follows:  
+
| The syntax of '''switch''' is as follows:  
 
   
 
   
 
|-
 
|-
−
| 05.30
+
| 05:30
 
|  use '''Switch''' semicolon
 
|  use '''Switch''' semicolon
  
 
|-
 
|-
−
|  05.32
+
|  05:32
−
| Press '''Enter'''  
+
| press '''Enter'''  
  
 
|-
 
|-
−
|  05.34
+
|  05:34
−
| '''switch ''' space open bracket '''dollar value''' close bracket space open curly bracket  
+
| '''switch''' space open bracket '''$ (dollar) value''' close bracket space open curly bracket  
  
 
|-
 
|-
−
|05.42
+
|05:42
−
|Press '''Enter '''
+
|press '''Enter '''
 
   
 
   
 
|-
 
|-
−
|  05.44
+
|  05:44
−
|  '''case ''' space 1 space open curly bracket ''' executes when dollar value equal to 1''' close curly bracket.  
+
|  '''case''' space 1 space open curly bracket '''executes when dollar value equal to 1''' close curly bracket.  
 
   
 
   
 
|-
 
|-
−
|  05.53
+
|  05:53
−
| Press '''Enter'''  
+
| Press '''Enter'''.
  
 
|-
 
|-
−
|05.55
+
|05:55
−
|'''case ''' space single quote '''a ''' single quote space open curly bracket ''' executes when dollar value equal to'''  single quote ''' a ''' single quote close curly bracket  
+
|'''case''' space single quote '''a ''' single quote space open curly bracket ''' executes when dollar value equal to'''  single quote ''' a ''' single quote close curly bracket  
 
   
 
   
 
|-
 
|-
−
| 06.09
+
| 06:09
−
| Press ''' Enter '''
+
| Press ''' Enter '''. ''' else''' space open curly bracket ''' executes when dollar value does not match any of the cases '''
−
 
+
 
   
 
   
 
|-
 
|-
−
| 06.10
+
|06:18
−
|''' else''' space open curly bracket ''' executes when dollar value does not match any of the cases '''
+
|close curly bracket. Press '''Enter '''.
−
+
−
|-
+
−
|06.18
+
−
|Close curly bracket
+
  
 
|-
 
|-
−
|06.19
+
| 06:20
−
|Press '''Enter '''
+
| Close curly bracket.
−
 
+
−
+
−
|-
+
−
| 06.20
+
−
| close curly bracket  
+
  
 
|-
 
|-
−
|  06.22
+
|  06:22
 
| Let us understand '''switch''' using a sample program.  
 
| Let us understand '''switch''' using a sample program.  
 
   
 
   
 
|-
 
|-
−
|  06.26
+
|  06:26
−
|  Open the Terminal and type  
+
|  Open the Terminal and type:
 
   
 
   
 
|-
 
|-
−
|06.29
+
|06:29
 
| ''' gedit sampleSwitch dot pl space ampersand'''
 
| ''' gedit sampleSwitch dot pl space ampersand'''
 
   
 
   
 
|-
 
|-
−
|06.36
+
|06:36
−
|and press '''Enter'''
+
|and press '''Enter'''.
 
   
 
   
 
|-
 
|-
−
|06.38
+
|06:38
−
  |Now, type the sample program as shown on the screen.  
+
|Now, type the sample program as shown on the screen.  
 
 
 
 
 
|-
 
|-
−
| 06.43
+
| 06:43
 
|  Let us understand how the ''' switch''' statement works.  
 
|  Let us understand how the ''' switch''' statement works.  
 
   
 
   
 
|-
 
|-
−
|06.46
+
|06:46
 
| The '''use Switch''' statement includes the '''Switch''' module inside the '''Perl''' code.  
 
| The '''use Switch''' statement includes the '''Switch''' module inside the '''Perl''' code.  
  
 
|-
 
|-
−
|06.54
+
|06:54
−
| Note: We will learn about '''use keyword''' in detail in subsequent tutorials.  
+
| Note: We will learn about '''use keyword''', in detail, in subsequent tutorials.  
  
 
|-
 
|-
−
|07.00
+
|07:00
−
| Now we'll test the different cases.   
+
| Now we will test the different cases.   
  
 
|-
 
|-
−
|07.03
+
|07:03
−
| We have assigned ''' 'Perl' ''' to the variable ''' $var'''
+
| We have assigned 'Perl' to the variable '''$var'''.
 
   
 
   
 
|-
 
|-
−
|07.08
+
|07:08
−
| The value in variable ''' $var''' is checked in the switch statement.  
+
| The value in variable '''$var''' is checked in the '''switch''' statement.  
  
 
|-
 
|-
−
|07.14
+
|07:14
−
| In the first case, it matches with the case ''' 'Perl'.'''
+
| In the first case, it matches with the case 'Perl'.  
  
 
|-
 
|-
−
|07.19
+
|07:19
−
| So the code written against this '''case''' will be executed.  
+
| So, the code written against this '''case''' will be executed.  
  
 
|-
 
|-
−
|07.24
+
|07:24
 
| Press ''' ctrl+s''' to '''save''' the file.  
 
| Press ''' ctrl+s''' to '''save''' the file.  
  
 
|-
 
|-
−
|07.27
+
|07:27
 
| Now, switch to terminal and execute the script  
 
| Now, switch to terminal and execute the script  
  
 
|-
 
|-
−
|07.31
+
|07:31
 
| '''perl sampleSwitch.pl'''
 
| '''perl sampleSwitch.pl'''
  
 
|-
 
|-
−
|07.36
+
|07:36
−
| press '''Enter'''  
+
| press '''Enter'''.
  
 
|-
 
|-
−
|07.38
+
|07:38
 
| The following output is shown on the terminal
 
| The following output is shown on the terminal
  
 
|-
 
|-
−
|07.41
+
|07:41
−
|''' I am Perl '''
+
|"I am Perl"
−
 
+
  
 
|-
 
|-
−
|07.43
+
|07:43
 
| Switch back to ''' sampleSwitch.pl''' in '''gedit.'''  
 
| Switch back to ''' sampleSwitch.pl''' in '''gedit.'''  
  
 
|-
 
|-
−
|07.48
+
|07:48
−
| Now, let us assign ''' 'Linux' ''' to the variable ''' $var '''
+
| Now, let us assign 'Linux' to the variable '''$var'''.
  
 
|-
 
|-
−
|07.52
+
|07:52
−
|Press ''' Ctrl S''' to save the file.
+
|Press '''Ctrl+S''' to '''save''' the file.
  
 
|-
 
|-
−
|07.57
+
|07:57
−
| Again, the value of variable ''' $var''' will be checked in switch.  
+
| Again, the value of variable ''' $var''' will be checked in '''switch'''.  
  
 
|-
 
|-
−
|08.03
+
|08:03
−
| It matches with the case ''' 'Linux' '''
+
| It matches with the case 'Linux'.
  
 
|-
 
|-
−
|08.05
+
|08:05
−
| So code written against this case will get executed.  
+
| So, code written against this '''case''' will get executed.  
  
 
|-
 
|-
−
|08.10
+
|08:10
−
| Now, switch to terminal and execute the script  
+
| Now, switch to terminal and execute the script.
  
 
|-
 
|-
−
|08.15
+
|08:15
 
| '''perl sampleSwitch.pl'''
 
| '''perl sampleSwitch.pl'''
  
 
|-
 
|-
−
|08.19
+
|08:19
−
| Press '''Enter'''
+
| press '''Enter'''.
  
 
|-
 
|-
−
|08.21
+
|08:21
−
| The following output is shown on the terminal  
+
| The following output is shown on the terminal.
  
 
|-
 
|-
−
|08.24
+
|08:24
−
| ''' I am Linux'''
+
| "I am Linux"
−
 
+
  
 
|-
 
|-
−
|08.26
+
|08:26
−
| Switch to ''' sampleSwitch.pl''' in ''' gedit.'''  
+
| Switch to '''sampleSwitch.pl''' in ''' gedit.'''  
  
 
|-
 
|-
−
|08.30
+
|08:30
−
| Similarly, if variable ''' $var''' has value ''' 'Java' ''', then second case will be checked.  
+
| Similarly, if variable '''$var''' has value 'Java' then second '''case''' will be checked.  
  
 
|-
 
|-
−
|08.38
+
|08:38
−
| Now, let us assign ''' 'English' ''' to the variable ''' $var'''
+
| Now, let us assign 'English' to the variable '''$var'''.
  
 
|-
 
|-
−
|08.42
+
|08:42
−
| Again, the value of variable ''' $var ''' will be checked in switch.  
+
| Again, the value of variable '''$var ''' will be checked in '''switch'''.  
  
 
|-
 
|-
−
|08.47
+
|08:47
 
|It does not match any of the  ''' case''' statements.  
 
|It does not match any of the  ''' case''' statements.  
  
 
|-
 
|-
−
|08.50
+
|08:50
−
| So the ''' else ''' statement will be executed.  
+
| So, the '''else''' statement will be executed.  
  
 
|-
 
|-
−
|08.54
+
|08:54
−
| Now, switch to terminal and execute the script  
+
| Now, switch to terminal and execute the script.
  
 
|-
 
|-
−
|09.00
+
|09:00
−
| ''' perl sampleSwitch.pl'''
+
| '''perl sampleSwitch.pl'''
  
 
|-
 
|-
−
|09.07
+
|09:07
−
| and Press ''' Enter'''
+
| and press '''Enter'''.
  
 
|-
 
|-
−
|09.09
+
|09:09
−
| The following output is shown on the terminal -
+
| The following output is shown on the terminal: 
  
 
|-
 
|-
−
|09.12
+
|09:12
−
|''' I am not a computer language '''
+
|"I am not a computer language"
−
 
+
  
 
|-
 
|-
−
|09.17
+
|09:17
−
| The 3 cases imply that:  
+
| The three cases imply that:  
  
 
|-
 
|-
−
|09.20
+
|09:20
−
| The value of the expression decides the ''' case ''' to be executed  
+
| The value of the expression decides the '''case''' to be executed.
  
 
|-
 
|-
−
|09.25
+
|09:25
−
| Only the valid ''' case''' will be executed and  
+
| Only the valid '''case''' will be executed and  
  
 
|-
 
|-
−
|09.28
+
|09:28
−
| When there is no valid '''case''', then the default ''' else ''' case will be executed  
+
| when there is no valid '''case''' then the default '''else''' '''case''' will be executed.
  
 
|-
 
|-
−
|09.35
+
|09:35
−
| It is not mandatory to write the '''else case. '''
+
| It is not mandatory to write the '''else case.'''
  
 
|-
 
|-
−
|09.39
+
|09:39
−
| In such a scenario,  
+
| In such scenario,  
  
 
|-
 
|-
−
|09.41
+
|09:41
 
| if none of the ''' cases''' match  
 
| if none of the ''' cases''' match  
  
 
|-
 
|-
−
|09.44
+
|09:44
−
| then there will be no output from the ''' switch''' statement.  
+
| then there will be no output from the '''switch''' statement.  
  
 
|-
 
|-
−
|09.48
+
|09:48
−
| Here is another assignment for you -
+
| Here is another assignment for you:
  
 
|-
 
|-
−
|09.50
+
|09:50
 
| Re-write the previous assignment  
 
| Re-write the previous assignment  
  
 
|-
 
|-
−
|09.53
+
|09:53
−
| given earlier in this tutorial using ''' switch''' statement.  
+
| given earlier, in this tutorial, using ''' switch''' statement.  
−
 
+
  
 
|-
 
|-
−
|09.57
+
|09:57
 
| Let us summarize.  
 
| Let us summarize.  
  
 
|-
 
|-
−
|09.59
+
|09:59
−
| In this tutorial, we have learnt -
+
| In this tutorial, we have learnt: 
−
 
+
  
 
|-
 
|-
−
|10.01
+
|10:01
 
| ''' if-elsif-else''' statement and  
 
| ''' if-elsif-else''' statement and  
−
 
−
 
  
 
|-
 
|-
−
|10.04
+
|10:04
−
| '''switch''' statement in '''Perl '''
+
| '''switch''' statement in '''Perl ''' using sample programs.
  
 
|-
 
|-
−
|10.05
+
|10:08
−
| '''using sample programs. '''
+
|Watch the video available at the following link.
−
 
+
 
 
|-
 
|-
−
|10.08
+
|10:12
−
|Watch the video available at the following link
+
|It summarizes the Spoken Tutorial project.
−
+
 
   
 
   
 
|-
 
|-
−
|10.12
+
|10:15
−
|It summaries the Spoken Tutorial project
+
|If you do not have good bandwidth, you can download and watch it.
−
+
 
   
 
   
 
|-
 
|-
−
|10.15
+
| 10:20
−
|If you do not have good bandwidth, you can download and watch it
+
|The Spoken Tutorial project team:  Conducts workshops using spoken tutorials.
 
   
 
   
 
|-
 
|-
−
| 10.20
+
|10:25
−
|  The Spoken Tutorial Project Team  Conducts workshops using spoken tutorials
+
|Gives certificates to those who pass an online test.
−
+
 
   
 
   
 
|-
 
|-
−
|10.25
+
|10:30
−
|Gives certificates to those who pass an online  test
+
|For more details, please write to: contact at spoken hyphen tutorial dot org.
−
+
 
   
 
   
 
|-
 
|-
−
|10.30
+
| 10:36
−
|For more details, please write to contact at spoken hyphen tutorial dot org
+
|"Spoken Tutorial" project is a part of the "Talk to a Teacher" project.
 
   
 
   
 
|-
 
|-
−
| 10.36
+
|10:40
−
|  Spoken Tutorial Project is a part of the Talk to a  Teacher project
+
−
+
−
+
−
|-
+
−
|10.40
+
 
|It is supported by the National Mission on Education through ICT, MHRD, Government of India.
 
|It is supported by the National Mission on Education through ICT, MHRD, Government of India.
−
 
 
   
 
   
 
|-
 
|-
−
|10.47
+
|10:47
−
|More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro
+
|More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
 
   
 
   
 
|-
 
|-
−
| 10.58
+
| 10:58
−
| Hope you enjoyed this Perl tutorial.  
+
| Hope you enjoyed this '''PERL''' tutorial.  
 
   
 
   
 
|-
 
|-
−
|11.00
+
|11:00
−
|This is Amol signing off.
+
|This is Amol, signing off.
−
+
 
   
 
   
 
|-
 
|-
−
|11.03
+
|11:03
 
|Thanks for joining.
 
|Thanks for joining.
 
   
 
   
 
|}
 
|}

Latest revision as of 15:37, 10 March 2017

Time Narration
00:00 Welcome to the spoken tutorial on if-elsif-else and switch conditional statements in PERL.
00:07 In this tutorial, we will learn about
00:10 the if-elsif-else statement and switch statement in Perl .
00:15 I am using Ubuntu Linux 12.04 operating system and Perl 5.14.2.
00:22 I will also be using the gedit Text Editor.
00:25 You can use any text editor of your choice.
00:29 You should have basic knowledge of variables and comments in Perl
00:34 and knowledge of for, foreach, while and do-while loops and
00:38 if and if-else statements will be an added advantage.
00:43 Please go through the relevant spoken tutorials on the Spoken Tutorial website.
00:48 If-elsif-else statement in Perl can be used
00:52 to test multiple conditions and
00:54 when all conditions fail then it executes the default else block.
00:59 The syntax of if-elsif-else statement is as follows.
01:04 if space open bracket condition1 close bracket space open curly bracket press Enter
01:13 piece of code to be executed when the condition is true semicolon
01:18 press Enter .
01:20 Close curly bracket space elsif space open bracket condition2 close bracket space open curly bracket
01:30 press Enter , another piece of code semicolon
01:33 to be executed when elsif condition is true
01:37 press Enter .
01:39 Close curly bracket space else space open curly bracket
01:44 Enter. Code to be executed when both the above conditions are false semicolon
01:51 press Enter .Close curly bracket.
01:55 First, the if condition is checked and executed if the condition1 is true.
02:01 If not, then the else if condition is checked and executed if it is true.
02:06 Otherwise, the code within else block is executed.
02:11 Now let us look at an example of if-elsif-else statement.
02:16 Open the Terminal and type:
02:19 gedit conditionalBlocks dot pl space ampersand
02:26 and press Enter.
02:28 This will open the " conditionalBlocks.pl" file in gedit.
02:33 Type the following piece of code as displayed on the screen.
02:38 We have assigned the value 'Perl' to the variable language.
02:44 Note that eq is string comparison operator.
02:49 And then we have various conditions that we want to check.
02:55 Now, press Ctrl+s to save the file.
02:58 Then switch to terminal and execute file directly.
03:02 Type: perl conditionalBlocks dot pl
03:09 Note: I am skipping the compilation step. It is not a mandatory step for executing Perl scripts.
03:16 If there is any compilation error,
03:18 execution will throw an error and will stop execution of script.
03:23 Now press Enter.
03:25 The output shown on the terminal is
03:27 "Hi, I am Perl"
03:29 Now, let us look at our next case.
03:31 Switch to gedit.
03:33 Assign 'Java' to variable language as shown.
03:37 Press Ctrl+s to save the file.
03:40 Switch to the terminal and execute the file.
03:43 Type: perl conditionalBlocks dot pl
03:50 and press Enter.
03:53 The output shown on the terminal is "Hi, I am Java".
03:59 Again let us switch back to gedit.
04:03 Now, let us assign 'English' to the language variable.
04:07 Press ctrl+s to save the file.
04:09 Switch to the terminal and execute the file.
04:13 Type: perl conditionalBlocks dot pl
04:18 and press Enter. The output shown on the terminal is:
04:22 "I am not a computer language".
04:27 The three cases imply that
04:29 only one if block that satisfies the condition will be executed.
04:35 Otherwise the default else block will get executed.
04:39 We can have multiple elsif conditions as per our requirement, like this.
04:46 Here is an assignment for you -
04:48 Write an if-elsif-else statement to print
04:51 “I am a Science graduate” if stream is 'science'
04:55 “I am a Commerce graduate” if stream is 'commerce'
04:59 “I am an Arts graduate” if stream is neither 'science' nor 'commerce'.
05:06 Now let us learn about the switch statement.
05:10 Till Perl 5.8, there was no switch statement in Perl.
05:14 After that, Switch module was introduced
05:18 which provided the functionality of switch statement.
05:22 Note: Modules in Perl will be covered in subsequent tutorials.
05:27 The syntax of switch is as follows:
05:30 use Switch semicolon
05:32 press Enter
05:34 switch space open bracket $ (dollar) value close bracket space open curly bracket
05:42 press Enter
05:44 case space 1 space open curly bracket executes when dollar value equal to 1 close curly bracket.
05:53 Press Enter.
05:55 case space single quote a single quote space open curly bracket executes when dollar value equal to single quote a single quote close curly bracket
06:09 Press Enter . else space open curly bracket executes when dollar value does not match any of the cases
06:18 close curly bracket. Press Enter .
06:20 Close curly bracket.
06:22 Let us understand switch using a sample program.
06:26 Open the Terminal and type:
06:29 gedit sampleSwitch dot pl space ampersand
06:36 and press Enter.
06:38 Now, type the sample program as shown on the screen.
06:43 Let us understand how the switch statement works.
06:46 The use Switch statement includes the Switch module inside the Perl code.
06:54 Note: We will learn about use keyword, in detail, in subsequent tutorials.
07:00 Now we will test the different cases.
07:03 We have assigned 'Perl' to the variable $var.
07:08 The value in variable $var is checked in the switch statement.
07:14 In the first case, it matches with the case 'Perl'.
07:19 So, the code written against this case will be executed.
07:24 Press ctrl+s to save the file.
07:27 Now, switch to terminal and execute the script
07:31 perl sampleSwitch.pl
07:36 press Enter.
07:38 The following output is shown on the terminal
07:41 "I am Perl"
07:43 Switch back to sampleSwitch.pl in gedit.
07:48 Now, let us assign 'Linux' to the variable $var.
07:52 Press Ctrl+S to save the file.
07:57 Again, the value of variable $var will be checked in switch.
08:03 It matches with the case 'Linux'.
08:05 So, code written against this case will get executed.
08:10 Now, switch to terminal and execute the script.
08:15 perl sampleSwitch.pl
08:19 press Enter.
08:21 The following output is shown on the terminal.
08:24 "I am Linux"
08:26 Switch to sampleSwitch.pl in gedit.
08:30 Similarly, if variable $var has value 'Java' then second case will be checked.
08:38 Now, let us assign 'English' to the variable $var.
08:42 Again, the value of variable $var will be checked in switch.
08:47 It does not match any of the case statements.
08:50 So, the else statement will be executed.
08:54 Now, switch to terminal and execute the script.
09:00 perl sampleSwitch.pl
09:07 and press Enter.
09:09 The following output is shown on the terminal:
09:12 "I am not a computer language"
09:17 The three cases imply that:
09:20 The value of the expression decides the case to be executed.
09:25 Only the valid case will be executed and
09:28 when there is no valid case then the default else case will be executed.
09:35 It is not mandatory to write the else case.
09:39 In such scenario,
09:41 if none of the cases match
09:44 then there will be no output from the switch statement.
09:48 Here is another assignment for you:
09:50 Re-write the previous assignment
09:53 given earlier, in this tutorial, using switch statement.
09:57 Let us summarize.
09:59 In this tutorial, we have learnt:
10:01 if-elsif-else statement and
10:04 switch statement in Perl using sample programs.
10:08 Watch the video available at the following link.
10:12 It summarizes the Spoken Tutorial project.
10:15 If you do not have good bandwidth, you can download and watch it.
10:20 The Spoken Tutorial project team: Conducts workshops using spoken tutorials.
10:25 Gives certificates to those who pass an online test.
10:30 For more details, please write to: contact at spoken hyphen tutorial dot org.
10:36 "Spoken Tutorial" project is a part of the "Talk to a Teacher" project.
10:40 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:47 More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
10:58 Hope you enjoyed this PERL tutorial.
11:00 This is Amol, signing off.
11:03 Thanks for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Sandhya.np14

Retrieved from "https://script.spoken-tutorial.org/index.php?title=PERL/C2/More-Conditional-statements/English-timed&oldid=33138"