Difference between revisions of "BASH/C2/Basics-of-Shell-Scripting/English-timed"

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|-
 
|-
 
| 00:09
 
| 00:09
|* '''System variables'''
+
|'''System variables'''
  
 
|-
 
|-
 
| 00:11
 
| 00:11
|* '''User defined variables''' and
+
| '''User defined variables''' and
  
 
|-
 
|-
 
| 00:13
 
| 00:13
|* Accepting user input via keyboard.
+
| Accepting user input via keyboard.
  
 
|-
 
|-
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|-
 
|-
 
| 00:23
 
| 00:23
|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.
  
 
|-
 
|-
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|-
 
|-
 
| 00:32
 
| 00:32
|* '''Ubuntu Linux 12.04''' Operating System and  
+
| '''Ubuntu Linux 12.04''' Operating System and  
  
 
|-
 
|-
 
| 00:35
 
| 00:35
|* '''GNU Bash''' version '''4.1.10'''
+
| '''GNU Bash''' version '''4.1.10'''
  
 
|-
 
|-
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|-
 
|-
 
|00:49
 
|00:49
| * '''Bash variables''' provide temporary storage for information.
+
| '''Bash variables''' provide temporary storage for information.
  
 
|-
 
|-
 
| 00:55
 
| 00:55
|* These '''variables''' can be used within the lifespan of the program.
+
| These '''variables''' can be used within the lifespan of the program.
  
 
|-
 
|-
 
| 01:01
 
| 01:01
|* There are two types of variables:  
+
| There are two types of variables: '''System variables''','''User defined variables '''.
# '''System variables'''
+
# '''User defined variables '''.
+
  
 
|-
 
|-
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|-
 
|-
 
| 01:20
 
| 01:20
|* '''BASH_VERSION '''
+
| '''BASH_VERSION '''. '''HOSTNAME '''
 
+
|-
+
| 01:21
+
|* '''HOSTNAME '''
+
  
 
|-
 
|-
 
| 01:23
 
| 01:23
|* '''HOME etc.'''
+
| '''HOME etc.'''
  
 
|-
 
|-
 
| 01:25
 
| 01:25
| Let us open the terminal by pressing '''Ctrl Alt''' and '''T''' keys simultaneously  on your keyboard.
+
| Let us open the '''terminal''' by pressing '''Ctrl, Alt''' and '''T''' keys simultaneously  on your keyboard.
  
 
|-
 
|-
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|-
 
|-
 
|01:53
 
|01:53
|Let me clear the prompt.
+
|Let me clear the '''prompt'''.
  
 
|-
 
|-
 
| 01:55
 
| 01:55
| Now, type: '''echo''' space within double quotes '''dollar sign''' '''HOSTNAME'''.
+
| Now, type: '''echo''' space within double quotes dollar sign '''HOSTNAME'''
  
 
|-
 
|-
 
| 02:01
 
| 02:01
|and now press '''Enter.'''
+
| now press '''Enter.'''
  
 
|-
 
|-
 
| 02:04
 
| 02:04
|The '''hostname''' of the system will be displayed.
+
|The '''hostname''' of the '''system''' will be displayed.
  
 
|-
 
|-
 
| 02:07
 
| 02:07
| Now let's find out the full path of '''home'''directory.
+
| Now let's find out the full '''path''' of '''home'''directory.
  
 
|-
 
|-
 
| 02:11
 
| 02:11
| Type:  '''echo''' space within double quotes '''dollar sign HOME'''(in capital).  
+
| Type:  '''echo''' space within double quotes dollar sign '''HOME'''(in capital).  
  
 
|-
 
|-
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|-
 
|-
 
| 02:21
 
| 02:21
|The full path of user's '''home''' directory will be displayed.
+
|The full '''path''' of user's '''home''' directory will be displayed.
  
 
|-
 
|-
 
|02:26
 
|02:26
| Now, type:
+
| Now, type:'''echo''' space within double quotes '''HOME''' (in capital).
 
+
|-
+
| 02:27
+
|'''echo''' space within double quotes '''HOME''' (in capital).
+
  
 
|-
 
|-
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|-
 
|-
 
| 02:34
 
| 02:34
|This will display only the '''HOME''' not the value of '''HOME''' variable.  
+
|This will display only the "HOME", not the value of '''HOME''' variable.  
  
 
|-
 
|-
 
|02:39
 
|02:39
|So, it is necessary to use '''dollar sign( '$') '''at the beginning of every variable to display its value.
+
|So, it is necessary to use dollar sign( $) at the beginning of every variable to display its value.
  
 
|-
 
|-
 
|02:48
 
|02:48
|Let us switch back to our slides.
+
|Let us switch back to our '''slides'''.
  
 
|-
 
|-
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|-
 
|-
 
| 02:53
 
| 02:53
|* These '''variables''' are created and maintained by users.
+
| These '''variables''' are created and maintained by users.
  
 
|-
 
|-
 
| 02:57
 
| 02:57
|* It is always a good idea to avoid '''uppercase''' for the names of '''user defined variables'''.  
+
| It is always a good idea to avoid '''uppercase''' for the names of '''user defined variables'''.  
  
 
|-
 
|-
 
| 03:05
 
| 03:05
|* This makes it easy to differentiate between '''user defined '''and '''system variables'''.
+
| This makes it easy to differentiate between '''user defined '''and '''system variables'''.
  
 
|-
 
|-
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|-
 
|-
 
| 03:14
 
| 03:14
| Type: '''username equal to sign sunita'''.
+
| Type: '''username''' equal to sign '''sunita'''
  
 
|-
 
|-
 
| 03:20
 
| 03:20
|Please note that there should not be any blank space between '''username''', '''equal to '''sign and '''sunita'''.
+
|Please note that there should not be any blank space between '''username''', equal to sign and '''sunita'''.
  
 
|-
 
|-
 
| 03:29
 
| 03:29
|Now, press '''Enter.'''
+
|Now, press '''Enter.''' To display the '''value''' of '''variable''' '''username''',
 
+
|-
+
| 03:30
+
| To display the value of '''variable''' '''username''',
+
  
 
|-
 
|-
 
| 03:33
 
| 03:33
|Type: '''echo''' space within double quotes '''dollar sign username'''.
+
|Type: '''echo''' space within double quotes dollar sign '''username'''  
  
 
|-
 
|-
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|-
 
|-
 
|03:50
 
|03:50
|Let us switch back to our '''slide'''.
+
|Let us switch back to our '''slides'''.
  
 
|-
 
|-
 
|03:52
 
|03:52
|'''unset'''- the value of '''variable''' can be unset by using the '''unset''' '''command'''.
+
|'''unset'''- the value of a variable can be unset by using the '''unset''' '''command'''.
  
 
|-
 
|-
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|-
 
|-
 
| 04:18
 
| 04:18
|Let us check. Type: '''echo''' space within double quotes '''dollar sign username ''', press '''Enter.'''
+
|Let us check. Type: '''echo''' space within double quotes dollar sign '''username ''' press '''Enter.'''
  
 
|-
 
|-
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|-
 
|-
 
|04:42
 
|04:42
| * In '''Shell '''script,''' user defined variables''' can be declared '''globally''' or '''locally. '''
+
| In '''Shell script,''' '''user defined variables''' can be declared '''global'''ly or '''local'''ly.
  
 
|-
 
|-
 
| 04:49
 
| 04:49
|* By default, all '''variables''' are '''global.'''
+
| By default, all '''variables''' are '''global.'''
  
 
|-
 
|-
 
| 04:52
 
| 04:52
|* This means, their values remain the same inside and outside the '''function'''.  
+
| This means, their values remain the same inside and outside the '''function'''.  
  
 
|-
 
|-
 
| 04:59
 
| 04:59
| Let us learn how to declare '''variables''' '''globally''' and '''locally.'''
+
| Let us learn how to declare '''variables''' '''global'''ly and '''local'''ly.
  
 
|-
 
|-
 
| 05:04
 
| 05:04
| Switch to the '''terminal '''and type:  
+
| Switch to the '''terminal '''. Type:  
  
 
|-
 
|-
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|-
 
|-
 
|05:23
 
|05:23
|and & (ampersand) is used to free up the prompt.
+
|and '&' (ampersand) is used to free up the '''prompt'''.
  
 
|-
 
|-
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|-
 
|-
 
| 05:30
 
| 05:30
| Type the code as shown here, in your''' g_(underscore)variable.sh '''file.
+
| Type the '''code''' as shown here, in your "g_(underscore)variable.sh" file.
  
 
|-
 
|-
 
| 05:35
 
| 05:35
| Let me explain the code now.
+
| Let me explain the '''code''' now.
  
 
|-
 
|-
 
| 05:38
 
| 05:38
| The first line with the '''hash '''and '''exclamation '''symbol, is a '''shebang''' or a '''bang''' line.
+
| The first line with the hash and exclamation symbol is a '''shebang''' or a '''bang''' line.
  
 
|-
 
|-
 
| 05:44
 
| 05:44
| '''username=sunita '''is the '''userdefined variable '''and it is declared '''globally.'''
+
| '''username=sunita '''is the '''userdefined variable '''and it is declared '''global'''ly.
  
 
|-
 
|-
 
| 05:51
 
| 05:51
| '''echo '''will display the '''string''' '''outside function: ''' and  
+
| '''echo '''will display the '''string''' '''"outside function:" ''' and  
  
 
|-
 
|-
 
| 05:55
 
| 05:55
|'''dollar username''' will print the value of the variable '''username.'''
+
|dollar '''username''' will '''print''' the value of the variable '''username.'''
  
 
|-
 
|-
 
| 06:00
 
| 06:00
|This is how we defined a '''function''' in '''BASH''' '''script'''.  
+
|This is how we define a '''function''' in '''BASH''' '''script'''.  
  
 
|-
 
|-
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|-
 
|-
 
| 06:12
 
| 06:12
|Here another message '''inside function '''will be displayed, along with the value of '''username.'''  
+
|Here, another message '''"inside function" '''will be displayed along with the value of '''username.'''  
  
 
|-
 
|-
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|-
 
|-
 
| 06:21
 
| 06:21
|This is our code. Now let's execute it.
+
|This is our code. Now let's '''execute''' it.
  
 
|-
 
|-
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|-
 
|-
 
|06:39
 
|06:39
|Now type: '''dot slash g_(Underscore)variable.sh'''
+
|Now, type: '''dot slash g_(Underscore)variable.sh'''
  
 
|-
 
|-
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|-
 
|-
 
| 06:47
 
| 06:47
| Observe the output.
+
| Observe the '''output'''. Outside the function, '''username '''takes the value '''sunita.'''  
 
+
|-
+
| 06:48
+
|Outside the function, '''username '''takes the value '''sunita.'''  
+
  
 
|-
 
|-
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|-
 
|-
 
| 06:59
 
| 06:59
| This is because '''username''' was declared '''globally '''outside the function.
+
| This is because '''username''' was declared '''global'''ly outside the function.
  
 
|-
 
|-
 
| 07:04
 
| 07:04
| Next, let us learn how to declare a '''variable''' '''locally'''.
+
| Next, let us learn how to declare a '''variable''' '''local'''ly.
  
 
|-
 
|-
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|-
 
|-
 
| 07:20
 
| 07:20
| Type the code as shown here, in your '''l_(underscore)variable.sh '''file.
+
| Type the code as shown here, in your "l_(underscore)variable.sh" file.
  
 
|-
 
|-
 
| 07:25
 
| 07:25
| Let me explain the code.
+
| Let me explain the '''code'''.
  
 
|-
 
|-
 
| 07:28
 
| 07:28
| The code is the same as before, except for an extra line of code inside the function.
+
| The code is the same as before except for an extra line of code inside the function.
  
 
|-
 
|-
 
|07:36
 
|07:36
| Inside the '''function''' block, we have a line-'''local''' '''space username equals to jack'''
+
| Inside the '''function''' block, we have a line- '''local''' '''space username equals to jack'''.
  
 
|-
 
|-
 
| 07:41
 
| 07:41
| This assigns a new '''value''' for the variable '''username locally'''.
+
| This assigns a new '''value''' for the variable '''username''' locally.
  
 
|-
 
|-
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|-
 
|-
 
| 07:50
 
| 07:50
|Let's make file executable.
+
|Let's make the file executable
  
 
|-
 
|-
 
| 07:52
 
| 07:52
|By typing '''chmod''' '''space plus x space l_variable.sh'''
+
|by typing '''chmod''' '''space plus x space l_variable.sh'''
  
 
|-
 
|-
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|-
 
|-
 
| 08:07
 
| 08:07
|Press '''Enter.'''
+
|Press '''Enter.'''The '''output''' is displayed.
 
+
|-
+
|08:08
+
|The output is displayed.
+
  
 
|-
 
|-
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|-
 
|-
 
| 08:20
 
| 08:20
|This is because '''username''' is assigned this value '''locally,''' within the function.
+
|This is because '''username''' is assigned this value locally, within the function.
  
 
|-
 
|-
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|-
 
|-
 
| 08:31
 
| 08:31
|The '''read''' '''command''' is used to accept input from the keyboard.
+
|The '''read''' '''command''' is used to accept '''input''' from the keyboard.
  
 
|-
 
|-
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|-
 
|-
 
| 09:08
 
| 09:08
|Press '''Enter.'''
+
|Press '''Enter.''' Type the code as shown here in your "read.sh" file.
 
+
|-
+
| 09:09
+
| Type the code as shown in your''' read.sh '''file.
+
  
 
|-
 
|-
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|-
 
|-
 
| 09:55
 
| 09:55
| press '''Enter.'''
+
| press '''Enter.''' Type: '''dot slash read.sh'''  press '''Enter.'''
 
+
|-
+
| 09:56
+
| Type: '''dot slash read.sh'''  press '''Enter.'''
+
  
 
|-
 
|-
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|-
 
|-
 
|10:20
 
|10:20
|Let us go back to our slide and summarize.  
+
|Let us go back to our '''slides''' and summarize.  
  
 
|-
 
|-
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|-
 
|-
 
| 10:26
 
| 10:26
|* '''System variables '''
+
|'''System variables ''', '''User defined variables''' and
 
+
|-
+
| 10:27
+
|* '''User defined variables'''
+
  
 
|-
 
|-
 
| 10:29
 
| 10:29
|* Accepting user input via keyboard.
+
| Accepting user input via keyboard.
  
 
|-
 
|-
 
| 10:33
 
| 10:33
|  As an assignment-
+
|  As an assignment- Write a simple '''Bash''' program to get the following '''system variables'''.
 
+
|-
+
|10:34
+
| Write a simple '''Bash''' program to get the following system variables.
+
  
 
|-
 
|-
 
| 10:38
 
| 10:38
|* '''pwd ''' and * '''logname'''.
+
| '''pwd ''' and * '''logname'''.
  
 
|-
 
|-
 
| 10:41
 
| 10:41
|* Write a simple '''Bash''' program
+
| Write a simple '''Bash''' program
  
 
|-
 
|-
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|-
 
|-
 
| 11:07
 
| 11:07
| The Spoken Tutorial Project team: Conducts workshops using spoken tutorials.  
+
| The Spoken Tutorial Project team:  
Gives certificates to those who pass an online test.  
+
Conducts workshops using spoken tutorials.Gives certificates to those who pass an online test.  
  
 
|-
 
|-
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|-
 
|-
 
|11:23
 
|11:23
| Spoken Tutorial Project is a part of the "Talk to a Teacher" project.
+
| '''Spoken Tutorial''' Project is a part of the '''Talk to a Teacher''' project.
  
 
|-
 
|-
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|-
 
|-
 
| 11:34
 
| 11:34
|More information on this mission is available at the link shown below:  http://spoken-tutorial.org\NMEICT-Intro
+
|More information on this mission is available at the link shown below:  http://spoken-tutorial.org/NMEICT-Intro
  
 
|-
 
|-

Latest revision as of 11:31, 12 May 2017

Time Narration
00:01 Welcome to the spoken tutorial on Basics of Shell Scripting.
00:05 In this tutorial, we will learn about:
00:09 System variables
00:11 User defined variables and
00:13 Accepting user input via keyboard.
00:16 To follow this tutorial, you should be familiar with Linux Operating System.
00:23 If not, for relevant tutorials, please visit our website which is as shown.
00:29 For this tutorial, I am using:
00:32 Ubuntu Linux 12.04 Operating System and
00:35 GNU Bash version 4.1.10
00:40 Please NoteGNU Bash version 4 or above is recommended for practice.
00:46 Let us start with an introduction to variables.
00:49 Bash variables provide temporary storage for information.
00:55 These variables can be used within the lifespan of the program.
01:01 There are two types of variables: System variables,User defined variables .
01:07 System variables: These are created and maintained by Linux Bash Shell itself.
01:14 They are defined by capital letters.
01:17 Commonly used system variables are-
01:20 BASH_VERSION . HOSTNAME
01:23 HOME etc.
01:25 Let us open the terminal by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
01:33 Now, type: set and press Enter.
01:38 This will display all the system variables.
01:42 Alternately, you can type env or printenv to view all the system variables.
01:53 Let me clear the prompt.
01:55 Now, type: echo space within double quotes dollar sign HOSTNAME
02:01 now press Enter.
02:04 The hostname of the system will be displayed.
02:07 Now let's find out the full path of homedirectory.
02:11 Type: echo space within double quotes dollar sign HOME(in capital).
02:18 Press Enter.
02:21 The full path of user's home directory will be displayed.
02:26 Now, type:echo space within double quotes HOME (in capital).
02:32 Press Enter.
02:34 This will display only the "HOME", not the value of HOME variable.
02:39 So, it is necessary to use dollar sign( $) at the beginning of every variable to display its value.
02:48 Let us switch back to our slides.
02:51 User Defined Variables:
02:53 These variables are created and maintained by users.
02:57 It is always a good idea to avoid uppercase for the names of user defined variables.
03:05 This makes it easy to differentiate between user defined and system variables.
03:12 Switch back to our terminal.
03:14 Type: username equal to sign sunita
03:20 Please note that there should not be any blank space between username, equal to sign and sunita.
03:29 Now, press Enter. To display the value of variable username,
03:33 Type: echo space within double quotes dollar sign username
03:40 press Enter.
03:42 This will display sunita on your terminal.
03:46 The value of a variable can be unset.
03:50 Let us switch back to our slides.
03:52 unset- the value of a variable can be unset by using the unset command.
03:59 The syntax for this is- unset variablename
04:03 Let's use the previous example where username is our variable.
04:08 Switch to the Terminal. Now type: unset space username, press Enter.
04:18 Let us check. Type: echo space within double quotes dollar sign username press Enter.
04:28 Nothing will be displayed on the terminal.
04:30 This means that the value of variable username has been removed.
04:36 Now switch back to our slide.
04:39 Global and local variables:
04:42 In Shell script, user defined variables can be declared globally or locally.
04:49 By default, all variables are global.
04:52 This means, their values remain the same inside and outside the function.
04:59 Let us learn how to declare variables globally and locally.
05:04 Switch to the terminal . Type:
05:07 gedit space g_(underscore)variable.sh space & (ampersand sign).
05:16 gedit is the text editor g_(underscore) variable.sh is our file name
05:23 and '&' (ampersand) is used to free up the prompt.
05:28 Press Enter.
05:30 Type the code as shown here, in your "g_(underscore)variable.sh" file.
05:35 Let me explain the code now.
05:38 The first line with the hash and exclamation symbol is a shebang or a bang line.
05:44 username=sunita is the userdefined variable and it is declared globally.
05:51 echo will display the string "outside function:" and
05:55 dollar username will print the value of the variable username.
06:00 This is how we define a function in BASH script.
06:04 We will discuss about functions in detail, in later tutorials.
06:09 This is the body of the function.
06:12 Here, another message "inside function" will be displayed along with the value of username.
06:19 Here, we call the function.
06:21 This is our code. Now let's execute it.
06:23 Come back to our Terminal.
06:26 Let me clear the prompt.
06:28 First we need to make our file executable.
06:31 Type: chmod space plus x space g_(underscore)variable.sh, press Enter.
06:39 Now, type: dot slash g_(Underscore)variable.sh
06:45 Press Enter.
06:47 Observe the output. Outside the function, username takes the value sunita.
06:53 Inside the function also, username takes the same value sunita.
06:59 This is because username was declared globally outside the function.
07:04 Next, let us learn how to declare a variable locally.
07:09 Type: gedit space l_(Underscore)variable.sh space & (ampersand sign).
07:18 Press Enter.
07:20 Type the code as shown here, in your "l_(underscore)variable.sh" file.
07:25 Let me explain the code.
07:28 The code is the same as before except for an extra line of code inside the function.
07:36 Inside the function block, we have a line- local space username equals to jack.
07:41 This assigns a new value for the variable username locally.
07:48 Now switch to the Terminal.
07:50 Let's make the file executable
07:52 by typing chmod space plus x space l_variable.sh
08:00 Press Enter.
08:02 Type: dot slash l_variable.sh
08:07 Press Enter.The output is displayed.
08:10 Outside the function, username takes the value sunita
08:15 whereas inside the function, username takes the value jack.
08:20 This is because username is assigned this value locally, within the function.
08:26 Now let us quickly see how to get user input via keyboard.
08:31 The read command is used to accept input from the keyboard.
08:36 It can also be used to assign an input value to a user defined variable.
08:41 The syntax of read command is-
08:44 read space hyphen p space within double quotes PROMPT
08:50 Please note that PROMPT is just a string that waits for user input.
08:55 You may replace it with your own string.
08:58 Now, switch to the terminal .
09:00 Type: gedit space read.sh space & (ampersand sign)
09:08 Press Enter. Type the code as shown here in your "read.sh" file.
09:14 Let me explain the code.
09:16 In this example, input is given from the keyboard by the user.
09:21 This is the bang line.
09:23 Here -p displays the prompt without a newline and takes input from the keyboard.
09:31 The user input will be stored in the variable username.
09:36 echo command displays the message
09:38 Hello and the name entered by the user via the keyboard.
09:43 So, let us execute the program.
09:45 Come back to our terminal.
09:49 Type: chmod space plus x space read.sh
09:55 press Enter. Type: dot slash read.sh press Enter.
10:01 Here it is displayed Enter username:
10:04 I will type ashwini, press Enter.
10:08 The message Hello ashwini is displayed.
10:13 ashwini was assigned as an input value to the user defined variable username.
10:20 Let us go back to our slides and summarize.
10:23 In this tutorial, we learnt:
10:26 System variables , User defined variables and
10:29 Accepting user input via keyboard.
10:33 As an assignment- Write a simple Bash program to get the following system variables.
10:38 pwd and * logname.
10:41 Write a simple Bash program
10:43 to ask username from user
10:46 to exit the program, if user does not enter anything within 10 seconds.
10:51 {Hint: read -(Hyphen)t 10 -(Hyphen)p}
10:56 Watch the video available at the link shown below.
10:59 It summarizes the Spoken-Tutorial project.
11:02 If you do not have good bandwidth, you can download and watch it.
11:07 The Spoken Tutorial Project team:

Conducts workshops using spoken tutorials.Gives certificates to those who pass an online test.

11:16 For more details, please write to contact@spoken-tutorial.org
11:23 Spoken Tutorial Project is a part of the Talk to a Teacher project.
11:27 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
11:34 More information on this mission is available at the link shown below: http://spoken-tutorial.org/NMEICT-Intro
11:40 The script has been contributed by FOSSEE and Spoken Tutorial teams.
11:44 This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14