BASH/C2/Nested-and-multilevel-if-elsif-statements/English-timed - Revision history

Pratik kamble at 10:28, 23 March 2017

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Sandhya.np14 at 12:40, 10 July 2015

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PoojaMoolya at 10:03, 5 December 2014

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PoojaMoolya at 12:00, 12 November 2014

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PoojaMoolya at 11:59, 12 November 2014

2014-11-12T11:59:08Z

PoojaMoolya: Created page with "{| style="border-spacing:0;" | | Time | | Narration |- | 00:00 | Dear friends, welcome to the spoken tutorial on '''Nested '''and''' multile..."

2014-11-12T11:58:22Z

Created page with "{| style="border-spacing:0;" | | <center>Time</center> | | <center>Narration</center> |- | 00:00 | Dear friends, welcome to the spoken tutorial on '''Nested '''and''' multile..."

New page

{| style="border-spacing:0;"
| | <center>Time</center>
| | <center>Narration</center>

|-
| 00:00
| Dear friends, welcome to the spoken tutorial on '''Nested '''and''' multilevel if statement''' in '''BASH.'''

|-
| 00:09
| In this tutorial, we will learn about the

|-
| 00:12
| '''Nested if-else '''and

|-
| 00:14
| '''Multilevel if-else statement'''

|-
| 00:17
| We will do this by using a few examples.

|-
|00:22
| To follow this tutorial, You should be familiar with '''Linux Operating System.'''

|-
| 00:28
| If not, for relevant tutorials please visit our website which is as shown

|-
| 00:35
| For this tutorial I am using

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| 00:38
| '''Ubuntu Linux 12.04''' OS and

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| 00:42
| '''GNU Bash''' version '''4.1.10'''

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| 00:46
| '''GNU Bash '''version '''4''' or above is recommended for practice.

|-
| 00:52
| Let us understand the flow of''' Nested if-else statement.'''

|-
| 00:57
| Here, if '''condition1''' is '''true''',''' '''then '''condition 2''' will be evaluated.

|-
| 01:04
| if '''condition2''' is '''true''', then''' statement 1''' will be executed.

|-
| 01:10
| That means, only when both the''' conditions''' '''1 '''and '''2 '''are '''true''' , then''' statement 1''' will be executed.

|-
| 01:19
| If''' condition1''' is '''false, '''then''' statement 3''' will be executed.

|-
| 01:25
| And if''' condition 2''' is '''false''', then''' statement 2''' will be executed.

|-
| 01:31
| Let's see an example.

|-
| 01:33
| I have written code in the file '''nestedifelse.sh'''

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| 01:38
| I will open it.

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| 01:40
| Let me explain the code now.

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| 01:43
| This is the ''' shebang line.'''

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| 01:45
| The variable '''NAME '''has been assigned the value '''anusha.'''

|-
| 01:50
| The variable '''PASSWORD '''has been assigned the value '''abc123.'''

|-
| 01:56
| The''' read '''command reads one line of data from the '''standard input.'''

|-
| 02:02
| '''- (hyphen) p''' flag displays the '''prompt'''.

|-
| 02:05
| The string after '''- (hyphen) p, “Enter name: ” '''will be displayed on the '''terminal'''.

|-
| 02:11
| '''myname '''is a variable which stores the text entered by user i.e. the user input.

|-
| 02:18
| The first '''if''' statement compares the two variables '''myname '''and '''NAME.'''

|-
| 02:24
| i.e. the user input and the value stored in variable''' Name '''i.e.''' anusha.'''

|-
| 02:31
| If the two values match, then the rest of the code in this '''if statement '''will be evaluated.

|-
| 02:38
| The '''read command''' reads and stores the entered password in variable '''mypassword'''.

|-
| 02:46
| Here, '''- (hyphen) s '''flag is for''' silent mode. '''

|-
| 02:49
| It means the text entered by the user will NOT be displayed on the '''terminal.'''

|-
| 02:56
| Here we have another set of '''if-else statements'''.

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| 02:59
| This set of '''if-else statements '''is nested within the first '''if '''.

|-
| 03:05
| The second '''if '''statement compares variables '''mypassword '''and '''PASSWORD.'''

|-
| 03:12
| '''echo''' displays the message''' “Welcome” '''on the '''terminal '''when the '''if condition '''is '''true;'''

|-
| 03:18
| i.e. the passwords match.

|-
| 03:21
| '''-e '''enables interpretation of '''backslash escapes.'''

|-
| 03:27
| '''\n '''stands for new line; which means the string “'''Welcome” '''will be printed on a new line.

|-
| 03:35
| When the '''if condition '''is not '''true,'''then the '''else condition '''will be executed;

|-
| 03:42
| i.e. when the passwords don't match, the '''else condition''' will be executed.

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| 03:48
| In this case, '''echo''' displays ''' “Wrong password”'''

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| 03:53
| '''fi '''ends the inner ''' if-else statement.'''

|-
| 03:57
| Coming back to our first '''if-else statement.'''

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| 04:01
| If the values in '''myname''' and '''NAME''' don't match, then this '''else statement '''will be executed.

|-
| 04:09
| This will '''echo '''the message''' “Wrong Name” '''on the '''terminal.'''

|-
| 04:14
| '''fi '''ends the outer''' if-else statement.'''

|-
| 04:18
| Now open the terminal window by pressing '''ctrl+alt and t''' keys simultaneously on your keyboard.

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| 04:27
| Make the file executable.

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| 04:29
| Type: '''chmod''' space''' plus x''' space''' nestedifelse.sh '''

|-
| 04:38
| Now type '''dot slash nestedifelse.sh'''

|-
| 04:43
| The program verifies two conditions

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| 04:46
| ie''' Name''' and '''Password'''

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| 04:48
| when it is executed on the '''terminal.'''

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| 04:52
| Here, the '''prompt''' displays “'''Enter Name:”'''

|-
| 04:55
| Let us type '''anusha.'''

|-
| 04:57
| As this '''condition '''is '''true''', the next '''if condition '''will be evaluated.

|-
| 05:02
| Now the '''prompt '''says ''' “Password:”'''

|-
| 05:05
| I will type the '''password''' as '''abc123'''

|-
| 05:10
| The''' password '''matches with the value in the variable '''PASSWORD.'''

|-
| 05:15
| So, the prompt displays the message “'''Welcome”.'''

|-
| 05:19
| Now let us execute the '''script''' again.

|-
| 05:21
| | Press the up arrow key.

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| 05:24
| Go to ''' dot slash nestedifelse.sh '''

|-
| 05:29
| Press '''Enter'''.

|-
| 05:31
| But this time we will enter the same name, with different password.

|-
| 05:37
| So I will enter the name as '''anusha '''and password as '''123.'''

|-
| 05:44
| The '''name''' values will match but the '''password''' values won't.

|-
| 05:49
| So, the message “'''Wrong password” '''will be displayed.

|-
| 05:53
| This proves that the '''nested else statement '''within the first '''if statement''' was executed.

|-
| 06:01
| Let's execute the script once more.

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| 06:04
| This time we will give the name as '''swati '''

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| 06:08
| The message “'''Wrong name” '''is displayed.

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| 06:12
| This is because the name '''swati''' does not match the previously declared value '''anusha.'''

|-
| 06:19
| The control comes out of the first '''if statement''' and executes the '''else statement'''.

|-
| 06:25
| This prints the message “'''Wrong name”.'''

|-
| 06:29
| Now let us look at '''multilevel if-else statement.'''

|-
|06:34
| if''' condition1''' is '''true, '''then''' statement1''' is executed.

|-
| 06:40
| If''' condition1''' is '''false, '''then''' condition 2''' is evaluated.

|-
| 06:46
| if''' condition2''' is '''true, '''then''' statement 2''' is executed .

|-
| 06:52
| And if''' condition 2''' is '''false, '''then''' condition N''' is evaluated.

|-
| 06:58
| If''' condition N''' is '''true,''' then''' statement N''' is executed.

|-
| 07:03
| And if''' Condition N''' is '''false,''' then''' statement X''' will be executed.

|-
| 07:10
| Let's look at an example.

|-
| 07:12
| I have a working example.

|-
| 07:14
| I will open it. Note that our file name is '''multilevel-ifelse dot sh'''.

|-
| 07:23
| Let us go through the code.

|-
| 07:25
| This is the''' shebang line.'''

|-
| 07:27
| '''mystring '''is a variable which stores the word, input by user, during execution.

|-
|07:34
| The '''if condition '''checks whether input string is '''null.'''

|-
| 07:39
|'''- (hyphen) z '''checks whether length of '''string''' is '''zero.'''

|-
| 07:44
|Type '''man test '''on''' terminal '''and explore various '''string ''' comparison.

|-
| 07:51
| This '''echo statement ''' will be printed, if nothing is entered.

|-
| 07:56
| The first '''elif condition '''checks whether the''' input string''' contains '''raj.'''

|-
| 08:03
|If it does, then this '''echo statement '''will be printed.

|-
| 08:08
|The '''wildcard character '''ensures that any word with''' raj '''in it, will be identified.

|-
| 08:15
| The next '''elif condition '''checks whether the''' input string''' contains the word '''jit.'''

|-
| 08:22
|If it does, then this '''echo statement '''will be printed.

|-
| 08:27
| The '''else condition '''will be executed when all the above '''conditions''' fail.

|-
| 08:33
|And it will display the message “'''Sorry! Input does not contain either 'raj' or 'jit'”'''

|-
| 08:41
| '''fi''' indicates the end of ''' multilevel if-else''' '''statement.'''

|-
| 08:46
| Let us now execute the program.

|-
| 08:48
| Come back to our '''terminal.'''

|-
| 08:51
|Type: '''chmod space plus x space multilevel-ifelse.sh '''

|-
| 09:00
| Type '''dot slash multilevel-ifelse.sh'''

|-
| 09:06
| We are prompted for an input.

|-
| 09:09
|Let us give different inputs and see what happens each time.

|-
| 09:14
| First I will press '''Enter '''without typing anything.

|-
| 09:19
| The message "'''Nothing was Entered '''" is displayed.

|-
| 09:22
|And the control comes out of the '''multilevel if-else statement.'''

|-
| 09:28
| Let me clear the prompt.

|-
| 09:30
|Let us try executing the script with a different input.

|-
| 09:34
|Press up arrow key.

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| 09:36
|Go to '''dot slash multilevel hyphen ifelse dot sh'''.

|-
| 09:41
|Press '''Enter'''.

|-
| 09:43
| The prompt displays '''"Enter a Word".'''

|-
| 09:45
|I will type '''abhijit.'''

|-
| 09:48
| The output displayed is '''“abhijit contains word jit”.'''

|-
| 09:53
|This shows that the control flowed to the third '''condition''' in our code.

|-
| 09:59
|The first two '''conditions''' did not match.

|-
|10:03
| The same logic is applicable for all the '''conditions.'''

|-
| 10:07
|Try executing the program with different inputs and check the results.

|-
| 10:13
|Let us summarise.

|-
| 10:15
|In this tutorial we learnt, the usage of

|-
| 10:18
| '''Nested If-else:''' with ''' Name''' and''' Password verification''' and

|-
| 10:23
|'''Multilevel if-else: String comparison''' program

|-
|10:28
|As an assignment, write a program to output different messages when number is

|-
| 10:34
| greater than 3,

|-
| 10:35
| lesser than 3,

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| 10:37
| or equal to 3,

|-
| 10:39
|or when the user input is empty

|-
| 10:42
| Watch the video available at the link shown below

|-
| 10:45
|It summarizes the Spoken Tutorial project

|-
| 10:48
|If you do not have good bandwidth, you can download and watch it

|-
| 10:53
| The Spoken Tutorial Project Team

|-
| 10:55
|Conducts workshops using spoken tutorials

|-
| 10:58
|Gives certificates to those who pass an online test

|-
| 11:02
|For more details, please write to contact@spoken-tutorial.org

|-
| 11:09
| Spoken Tutorial Project is a part of the Talk to a Teacher project

|-
| 11:13
|It is supported by the National Mission on Education through ICT, MHRD, Government of India

|-
| 11:20
|More information on this Mission is available at the link shown below

|-
|11:26
| The script has been contributed by FOSSEE and Spoken Tutorial Team.

|-
| 11:31
|This is Ashwini from IIT Bombay.

Thank you for joining.

|}

@@ Line 521: / Line 521: @@
 |-
 | 10:34
-|* greater than 3
+|greater than 3 lesser than 3
-−
-|-
-| 10:35
-|* lesser than 3
 |-
 | 10:37
-|* or equal to 3
+|or equal to 3
 |-
@@ Line 553: / Line 549: @@
 |-
 | 10:55
-|* Conducts workshops using spoken tutorials.
+|Conducts workshops using spoken tutorials.
 |-
 | 10:58
-|* Gives certificates to those who pass an online test.
+|Gives certificates to those who pass an online test.
 |-
@@ Line 581: / Line 577: @@
 |-
 | 11:31
-|This is Ashwini from IIT Bombay.
+|This is Ashwini from IIT Bombay.Thank you for joining.
-−
 Thank you for joining.
 |}

@@ Line 1: / Line 1: @@
 {| border = 1
-| | <center>Time</center>
+|'''Time'''
-| | <center>Narration</center>
+|'''Narration'''
 |-

@@ Line 29: / Line 29: @@
 |-
 | 00:28
-| If not, for relevant tutorials, please visit our website which is as shown
+| If not, for relevant tutorials, please visit our website which is as shown.
 |-

@@ Line 137: / Line 137: @@
 |-
 | 02:49
-| It means the text entered by the user will NOT be displayed on the '''terminal.'''
+| It means the text entered by the user will Not be displayed on the '''terminal.'''
 |-
@@ Line 165: / Line 165: @@
 |-
 | 03:27
-| '''\n '''stands for new line; which means the string “'''Welcome” '''will be printed on a new line.
+| '''\n '''stands for new line; which means the string '''Welcome” '''will be printed on a new line.
 |-
@@ Line 209: / Line 209: @@
 |-
 | 04:29
-| Type: '''chmod''' space''' plus x''' space''' nestedifelse.sh '''
+| Type: '''chmod''' space''' plus x''' space '''nestedifelse.sh '''
 |-
@@ Line 229: / Line 229: @@
 |-
 | 04:52
-|  Here, the '''prompt''' displays “'''Enter Name:”'''
+|  Here, the '''prompt''' displays '''Enter Name'''
 |-
@@ Line 241: / Line 241: @@
 |-
 |  05:02
-|  Now the '''prompt '''says ''' “Password:”'''
+|  Now the '''prompt '''says '''Password'''
 |-
@@ Line 253: / Line 253: @@
 |-
 | 05:15
-|  So, the prompt displays the message “'''Welcome”.'''
+|  So, the prompt displays the message '''Welcome'''
 |-
@@ Line 273: / Line 273: @@
 |-
 | 05:31
-|  But this time we will enter the same name, with different password.
+|  This time we will enter the same name, with different password.
 |-
@@ Line 285: / Line 285: @@
 |-
 |  05:49
-|  So, the message “'''Wrong password” '''will be displayed.
+|  So, the message '''Wrong password'''will be displayed.
 |-
@@ Line 313: / Line 313: @@
 |-
 |  06:25
-|  This prints the message “'''Wrong name”.'''
+|  This prints the message '''Wrong name.'''
 |-
@@ Line 321: / Line 321: @@
 |-
 |06:34
-| if''' condition1''' is '''true, '''then''' statement1''' is executed.
+| if ''' condition1''' is '''true,''' then '''statement1''' is executed.
 |-
 | 06:40
-| If''' condition1''' is '''false, '''then''' condition 2''' is evaluated.
+| If'''condition1''' is '''false''', then''' condition 2''' is evaluated.
 |-
 | 06:46
-| if''' condition2''' is '''true, '''then''' statement 2''' is executed .
+| if '''condition2''' is '''true''', then '''statement 2''' is executed .
 |-
@@ Line 353: / Line 353: @@
 |-
 | 07:14
-| I will open it.  Note that our file name is '''multilevel-ifelse dot sh'''.
+| I will open it.  Note that our file name is '''multilevel hyphen ifelse dot sh'''.
 |-
@@ Line 377: / Line 377: @@
 |-
 | 07:44
-|Type '''man test '''on''' terminal '''and explore various '''string ''' comparison.
+|Type '''man test ''' on '''terminal '''and explore various '''string ''' comparison.
 |-
@@ Line 385: / Line 385: @@
 |-
 | 07:56
-|  The first '''elif condition '''checks whether the''' input string''' contains '''raj.'''
+|  The first '''elif condition''' checks whether the''' input string''' contains '''raj.'''
 |-
 | 08:03
-|If it does, then this '''echo statement '''will be printed.
+|If it does, then this '''echo statement''' will be printed.
 |-
@@ Line 409: / Line 409: @@
 |-
 | 08:33
-|And it will display the message “'''Sorry! Input does not contain either 'raj' or 'jit'”'''
+|And it will display the message '''Sorry! Input does not contain either 'raj' or jit'''
 |-
@@ Line 425: / Line 425: @@
 |-
 | 08:51
-|Type: '''chmod space plus x space multilevel-ifelse.sh '''
+|Type: '''chmod space plus x space multilevel hyphen ifelse dot sh '''
 |-
 | 09:00
-|  Type '''dot slash multilevel-ifelse.sh'''
+|  Type '''dot slash multilevel hyphen ifelse dot sh'''
 |-
@@ Line 445: / Line 445: @@
 |-
 |  09:19
-|  The message "'''Nothing was Entered '''" is displayed.
+|  The message '''Nothing was Entered ''' is displayed.
 |-

@@ Line 262: / Line 262: @@
 | 05:21
 | | Press the up arrow key.
 |-
@@ Line 370: / Line 369: @@
 |-
 |07:34
- | The '''if condition '''checks whether input string is '''null.'''
+| The '''if condition '''checks whether input string is '''null.'''
 |-
@@ Line 443: / Line 442: @@
 | 09:14
 |  First I will press '''Enter '''without typing anything.
 |-
@@ Line 580: / Line 578: @@
 |11:26
 | The script has been contributed by FOSSEE and Spoken Tutorial Team.
 |-