Difference between revisions of "BASH/C2/Conditional-Loops/English-timed"

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'''Title of script:''' '''Basic If loop in BASH '''
 
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'''Author:''' Ashwini Patil
 
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'''Keywords: video tutorial, for loop, while loop'''
 
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{| border=1  
 
{| border=1  
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!Time  
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|'''Time'''
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!Narration  
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|'''Narration'''
 
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| 00:01
 
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|-
 
| 00:09   
 
| 00:09   
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| * '''for loop'''  
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|'''for loop'''  
  
 
|-
 
|-
 
| 00:11   
 
| 00:11   
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| * '''while loop'''<br/> with a few examples.
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|'''while loop'''<br/> with a few examples.
 
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| 00:15
 
| 00:15
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|-
 
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| 00:18
 
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| * '''Ubuntu Linux''' 12.04 '''Operating System '''
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|'''Ubuntu Linux''' 12.04 '''Operating System '''
  
 
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| 00:22
 
| 00:22
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| * '''GNU BASH''' version 4.1.10
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|'''GNU BASH''' version 4.1.10
  
 
|-
 
|-
 
| 00:26
 
| 00:26
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| Please note,'''GNU bash''' version '''4''' or above is recommended to practice this tutorial.
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| Please note, '''GNU bash''' version 4 or above is recommended to practice this tutorial.
  
 
|-
 
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|-
 
|-
 
| 01:45  
 
| 01:45  
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| First, we initialize '''i''' to '''1'''.
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| First, we initialize 'i' to 1.
  
 
|-
 
|-
 
| 01:48  
 
| 01:48  
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| Then we check whether '''i''' is less than or equal to '''number'''.
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| Then we check whether 'i' is less than or equal to '''number'''.
  
 
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|-
 
|-
 
| 02:03   
 
| 02:03   
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|  After this, we increment the '''value''' of '''i''' by '''1'''.
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|  After this, we increment the '''value''' of 'i' by 1.
  
 
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|-
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|-
 
|-
 
|  02:40   
 
|  02:40   
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| The '''sum''' that is calculated for each value of '''i''' is displayed.
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| The '''sum''' that is calculated for each value of 'i' is displayed.
  
 
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|-
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|-
 
|-
 
|  02:50
 
|  02:50
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| '''Sum of first n numbers is 15'''.
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| '''"Sum of first n numbers is 15"'''.
  
 
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|-
 
|-
 
|  02:57
 
|  02:57
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| Let me resize the windows.
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| Let me resize the '''windows'''.
  
 
|-
 
|-
 
|  03:00
 
|  03:00
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|  First, we have value of '''i''' as '''1'''.
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|  First, we have value of 'i' as 1.
  
 
|-
 
|-
 
|  03:04  
 
|  03:04  
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|  Then we check whether ''' 1 ''' is less than or equal to ''' 5.'''
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|  Then we check whether '''1''' is less than or equal to ''' 5.'''
  
 
|-
 
|-
 
|  03:10
 
|  03:10
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| Since the condition is '''True,''' we calculate '''sum''' as ''' 0 + 1.'''
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| Since the condition is '''True,''' we calculate the '''sum''' as '''0 + 1.'''
  
 
|-
 
|-
 
|  03:16
 
|  03:16
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| Now we have '''sum '''as '''1.'''
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| Now we have the '''sum '''as '''1.'''
  
 
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|-
 
|-
 
|  03:24  
 
|  03:24  
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|  Next, '''i''' is incremented by '''1''' and the new value of ''' i ''' is ''' 2.'''
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|  Next, 'i' is incremented by '''1''' and the new value of 'i' is '''2.'''
  
 
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|-
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|-
 
|-
 
| 03:44
 
| 03:44
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|    '''i ''' is then incremented by '''1''' and then the new value of ''' i''' is ''' 3.'''
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|    'i' is then incremented by '''1''' and then the new value of 'i' is '''3.'''
  
 
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|-
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|-
 
|-
 
| 03:55  
 
| 03:55  
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|  The '''script''' will continue to add the next value of ''' i ''' to the previous value in ''' sum.'''
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|  The '''script''' will continue to add the next value of 'i' to the previous value in ''' sum.'''
  
 
|-
 
|-
 
| 04:02  
 
| 04:02  
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| This will continue till '''<nowiki>i<=5</nowiki>''' is '''false.'''
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| This will continue till '''<nowiki>i<=5</nowiki>''' is '''False.'''
  
 
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|-
 
|-
 
| 04:20   
 
| 04:20   
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| I have written the '''code''' in this file and named it as '''for-loop.sh'''
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| I have written the '''code''' in this file and named it as '''for-loop.sh'''.
  
 
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|-
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|-
 
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| 04:35  
 
| 04:35  
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|  Then we have '''for loop'''.
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|  Then we have '''for''' loop.
  
 
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| '''./for-loop.sh'''
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| Type: '''./for-loop.sh'''
  
 
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|-
 
| 05:14   
 
| 05:14   
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|  Now, we will learn about ''' while loop.'''
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|  Now we will learn about ''' while loop.'''
  
 
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|  '''while condition'''
 
|  '''while condition'''
 
'''statement 1, 2, 3'''
 
'''statement 1, 2, 3'''
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End of '''while loop'''.
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end of '''while loop'''.
  
 
|-
 
|-
 
| 05:27
 
| 05:27
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| This means that the '''while loop''' will execute as long as the condition is '''True.'''
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| This means that the '''while''' loop will execute as long as the '''condition''' is '''True.'''
  
 
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|  05:37
 
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| Here I have named it as '''while.sh'''.
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| Here, I have named it as '''while.sh'''.
  
 
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|05:59
 
|05:59
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|  Next, we declare variables '''i''' and '''sum''' and initialize them to ''' 0 (zero).'''
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|  Next, we declare variables 'i' and '''sum''' and initialize them to 0 (zero).
  
 
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| 06:08
 
| 06:08
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| Here, we check whether '''i''' is '''less than or equal''' to value of '''number''' given by the user.
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| Here, we check whether 'i' is '''less than or equal''' to value of '''number''' given by the user.
  
 
|-
 
|-
 
| 06:17   
 
| 06:17   
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|  Then we calculate the '''sum''' by adding value of '''i''' to value of '''sum'''.
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|  Then we calculate the '''sum''' by adding value of 'i' to value of '''sum'''.
  
 
|-
 
|-
 
|  06:24  
 
|  06:24  
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|  Next, we increment the value of '''i''' with '''2'''.
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|  Next, we increment the value of 'i' with '''2'''.
  
 
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|  06:33  
 
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| And the '''while loop''' is repeated till the value of '''i''' exceeds the value of '''number.'''
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| And the '''while loop''' is repeated till the value of 'i' exceeds the value of '''number.'''
 
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| Let us execute the program.
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| Let us '''execute''' the program.
  
 
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|  07:06  
 
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| '''Sum of even numbers within the given range is 56.'''
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| '''"Sum of even numbers within the given range is 56".'''
  
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| 07:11  
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|-
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|  Let me resize the window and explain the '''output'''.
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| 07:11  
 +
|  Let me resize the '''window''' and explain the '''output'''.
  
 
|-
 
|-
 
| 07:14  
 
| 07:14  
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|  First we check whether '''i''' which is '''0,''' is less than or equal to the '''number''' which is '''15'''.
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|  First we check whether 'i' which is 0, is less than or equal to the '''number''' which is '''15'''.
  
 
|-
 
|-
 
|  07:24  
 
|  07:24  
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|  The '''condition''' is '''True.''' Hence '''sum''' will be '''0+0''' i.e '''0.'''
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|  The '''condition''' is '''True.''' Hence '''sum''' will be '0+0' i.e 0.
  
 
|-
 
|-
 
|  07:31
 
|  07:31
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| Now '''i''' will be incremented by '''2''' and the new value of ''' i ''' is ''' 2.'''
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| Now 'i' will be incremented by '''2''' and the new value of 'i' is ''' 2.'''
  
 
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|  07:52
 
|  07:52
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|  Again the value of '''i''' will be incremented by '''2'''.
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|  Again the value of 'i' will be incremented by '''2'''.
  
 
|-
 
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|  07:56
 
|  07:56
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| So, now value of '''i''' will be '''2+2''' i.e '''4.'''
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| So, now value of 'i' will be '''2+2''' i.e '''4.'''
  
 
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|  08:09
 
|  08:09
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|  In the same way, the '''script''' will continue to add '''2''' to the previous value of '''i, '''till it exceeds '''15'''.
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|  In the same way, the '''script''' will continue to add '''2''' to the previous value of 'i', till it exceeds '''15'''.
  
 
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| 08:27   
 
| 08:27   
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| Let us summarize.
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| Let us summarize. In this tutorial, we learned two different syntax of '''for loop ''' and we also learned about the '''while loop.'''
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+
−
|-
+
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| 08:28 
+
−
| In this tutorial, we learned two different syntax of '''for loop ''' and we also learned about the '''while loop.'''
+
  
 
|-
 
|-
 
| 08:37   
 
| 08:37   
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|   As an assignment -
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| As an assignment -find the sum of the first "n" prime numbers.
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+
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|-
+
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| 08:38 
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| find the sum of the first "n" prime numbers.
+
  
 
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| 08:56   
 
| 08:56   
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| Conducts workshops using spoken tutorials.  
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|Conducts workshops using spoken tutorials.  
  
 
|-
 
|-
 
| 09:00   
 
| 09:00   
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| Gives certificates to those who pass an online test.  
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|Gives certificates to those who pass an online test.  
  
 
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|-
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| 09:11  
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|09:11  
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| '''Spoken Tutorial''' Project is a part of the '''Talk to a Teacher''' project.
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|'''Spoken Tutorial''' Project is a part of the '''Talk to a Teacher''' project.
  
 
|-
 
|-
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| 09:14  
+
| 09:14  
 
| 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.
  

Latest revision as of 16:24, 23 March 2017

Time Narration
00:01 Dear friends, welcome to the spoken tutorial on loops in BASH.
00:07 In this tutorial, we will learn:
00:09 for loop
00:11 while loop
with a few examples.
00:15 To record this tutorial, I am using:
00:18 Ubuntu Linux 12.04 Operating System
00:22 GNU BASH version 4.1.10
00:26 Please note, GNU bash version 4 or above is recommended to practice this tutorial.
00:34 Let us start with an introduction to loops.
00:37 Loops are used to execute a group of statements repeatedly.
00:43 Let us see the syntax.
00:45 for expression 1, 2, 3
00:49 statement 1, 2, 3
00:51 and this is the end of for loop.
00:55 An alternate syntax of for loop is:
00:58 for variable in sequence/range
01:03 statement 1, 2, 3
01:06 and end of for loop.
01:09 Let us see an example of for loop using the first syntax.
01:14 In this program, we will calculate the sum of first n numbers.
01:20 Note that our filename is for.sh.
01:25 This is our shebang line.
01:28 The variable number will store the value given by user.
01:34 The value is an integer here.
01:37 Now, we initialize the variable sum as zero.
01:42 This is where we begin the for loop.
01:45 First, we initialize 'i' to 1.
01:48 Then we check whether 'i' is less than or equal to number.
01:54 Now here, we calculate the sum as sum plus i
02:00 and then we print it.
02:03 After this, we increment the value of 'i' by 1.
02:08 And then we check the condition till this condition is False.
02:14 On exiting the for loop, this message is printed.
02:19 Let us execute the program and observe what happens.
02:24 On the terminal, type - chmod +x for.sh
02:31 Then type: ./for.sh
02:36 I will enter 5 as the input number.
02:40 The sum that is calculated for each value of 'i' is displayed.
02:46 After that, the last line of the output is displayed:
02:50 "Sum of first n numbers is 15".
02:54 Now, let us see the flow of the program.
02:57 Let me resize the windows.
03:00 First, we have value of 'i' as 1.
03:04 Then we check whether 1 is less than or equal to 5.
03:10 Since the condition is True, we calculate the sum as 0 + 1.
03:16 Now we have the sum as 1.
03:20 Then we print sum i.e 1.
03:24 Next, 'i' is incremented by 1 and the new value of 'i' is 2.
03:31 Then we check whether 2 is less than or equal to 5.
03:36 The condition is True and now sum will be 1 + 2 i.e 3.
03:44 'i' is then incremented by 1 and then the new value of 'i' is 3.
03:51 And we get sum as 6.
03:55 The script will continue to add the next value of 'i' to the previous value in sum.
04:02 This will continue till i<=5 is False.
04:09 On exiting the for loop, the final message is printed.
04:14 Let us see another example of for loopusing the second syntax.
04:20 I have written the code in this file and named it as for-loop.sh.
04:27 This simple program will list the files in a directory.
04:32 This is the shebang line.
04:35 Then we have for loop.
04:37 'ls' command lists the directory content.
04:41 -1 (hyphen one) lists one file per line.
04:46 This will list all the files present in your home directory.
04:51 This is the end of for loop.
04:53 Let us execute the script on the terminal by typing -
04:58 chmod +x for-loop.sh
05:04 Type: ./for-loop.sh
05:09 This will display all the files present in the Home directory.
05:14 Now we will learn about while loop.
05:18 Let us understand the syntax first.
05:21 while condition

statement 1, 2, 3 end of while loop.

05:27 This means that the while loop will execute as long as the condition is True.
05:34 Let us see an example of while loop.
05:37 Here, I have named it as while.sh.
05:42 In this program, we will calculate the sum of even numbers within a given range.
05:49 Let us go through the code.
05:52 Here, we accept a number from the user and store it in variable number.
05:59 Next, we declare variables 'i' and sum and initialize them to 0 (zero).
06:06 Now, this is the while condition.
06:08 Here, we check whether 'i' is less than or equal to value of number given by the user.
06:17 Then we calculate the sum by adding value of 'i' to value of sum.
06:24 Next, we increment the value of 'i' with 2.
06:28 This will ensure that we only add the even numbers.
06:33 And the while loop is repeated till the value of 'i' exceeds the value of number.
06:40 When we exit the while loop, we print the sum of all the even numbers within the given range.
06:47 Let us execute the program.
06:50 Type on the terminal:
06:52 chmod +x while.sh
06:56 ./while.sh
07:00 I will give 15 as my input.
07:04 The last line of the output is:
07:06 "Sum of even numbers within the given range is 56".
07:11 Let me resize the window and explain the output.
07:14 First we check whether 'i' which is 0, is less than or equal to the number which is 15.
07:24 The condition is True. Hence sum will be '0+0' i.e 0.
07:31 Now 'i' will be incremented by 2 and the new value of 'i' is 2.
07:37 Then we check if 2 is less than or equal to 15.
07:43 The condition again is True; so we add 0+2.
07:49 Now sum has the value 2.
07:52 Again the value of 'i' will be incremented by 2.
07:56 So, now value of 'i' will be 2+2 i.e 4.
08:03 And the next value of sum will be 4+2 i.e 6.
08:09 In the same way, the script will continue to add 2 to the previous value of 'i', till it exceeds 15.
08:18 And we get the total value in sum as 56.
08:24 This brings us to the end of this tutorial.
08:27 Let us summarize. In this tutorial, we learned two different syntax of for loop and we also learned about the while loop.
08:37 As an assignment -find the sum of the first "n" prime numbers.
08:43 Watch the video available at the link shown below.
08:46 It summarizes the Spoken-Tutorial project.
08:50 If you do not have good bandwidth, you can download and watch it.
08:54 The Spoken Tutorial Project team:
08:56 Conducts workshops using spoken tutorials.
09:00 Gives certificates to those who pass an online test.
09:04 For more details, please write to contact@spoken-tutorial.org
09:11 Spoken Tutorial Project is a part of the Talk to a Teacher project.
09:14 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
09:22 More information on this mission is available at the link shown below.
09:28 The script has been contributed by Fossee and spoken-tutorial team.
09:34 This is Ashwini Patil from IIT Bombay, signing off.
09:38 Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Ranjana, Sandhya.np14

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