Difference between revisions of "BASH/C3/Basics-of-functions/English-timed"

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| Dear friends, welcome to the '''spoken tutorial''' on '''Basics of functions''' in '''Bash.'''
 
| Dear friends, welcome to the '''spoken tutorial''' on '''Basics of functions''' in '''Bash.'''
  
 
|-
 
|-
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| 00.08
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|00:08
 
| In this tutorial, we will learn:
 
| In this tutorial, we will learn:
  
 
|-
 
|-
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|  00:11
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|* Importance of '''Functions'''
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|Importance of '''Functions'''
 
|-
 
|-
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|  00:13
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|* To declare a''' function'''
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|To declare a''' function'''
 
|-
 
|-
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|  00:15
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|* To call a''' function'''
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|To call a''' function'''
 
|-
 
|-
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|  00:17
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|* Work flow of a '''function'''
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|Work flow of a '''function'''
 
|-
 
|-
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| 00.19
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|00:19
 
| with the help of an example.  
 
| with the help of an example.  
  
 
|-
 
|-
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| 00.22
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|00:22
 
| To follow this tutorial, you should have knowledge of '''Shell Scripting''' in''' BASH.'''
 
| To follow this tutorial, you should have knowledge of '''Shell Scripting''' in''' BASH.'''
  
 
|-
 
|-
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| 00.28
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|00:28
 
|If not, for relevant tutorials, please visit our website which is as shown. '''http://www.spoken-tutorial.org'''
 
|If not, for relevant tutorials, please visit our website which is as shown. '''http://www.spoken-tutorial.org'''
  
 
|-
 
|-
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| 00.34
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|00:34
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| For this tutorial, I am using''' Ubuntu Linux''' 12.04''' Operating System'''.  
+
|For this tutorial, I am using''' Ubuntu Linux''' 12.04''' Operating System'''.  
  
 
|-
 
|-
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| 00.40
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|00:40
 
|Till now we were using '''GNU BASH '''version 4.1.10
 
|Till now we were using '''GNU BASH '''version 4.1.10
  
 
|-
 
|-
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| 00.46
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|00:46
 
|From now onwards, we will use '''GNU BASH''' version 4.2
 
|From now onwards, we will use '''GNU BASH''' version 4.2
  
 
|-
 
|-
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| 00.52
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|00:52
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|Please note,''' GNU Bash version 4''' or above is recommended for practice.
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|Please note,''' GNU Bash''' version 4 or above is recommended for practice.
  
 
|-
 
|-
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| 00.58
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|00:58
 
| Let us see what is a''' function''' and its usage.
 
| Let us see what is a''' function''' and its usage.
  
 
|-
 
|-
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| 01.03
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|01:03
 
| A '''function''' is a collection of '''commands''' or an '''algorithm'''.
 
| A '''function''' is a collection of '''commands''' or an '''algorithm'''.
  
 
|-
 
|-
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| 01.08
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|01:08
 
| It is intended to do a specific task.
 
| It is intended to do a specific task.
  
 
|-
 
|-
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| 01.12
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|01:12
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| It is used to break up a complex program into separate tasks.
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| It is used to break-up a complex program into separate tasks.
  
 
|-
 
|-
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| 01.18
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|01:18
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| This improves overall script readability and ease of use.
+
|This improves overall script readability and ease of use.
  
 
|-
 
|-
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| 01.24
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|01:24
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| There are two syntaxes for '''function''' declaration.
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|There are two syntaxes for '''function''' declaration.
  
 
|-
 
|-
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|01:28
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| First syntax is-
+
| First syntax is-'''function space function_name'''
  
 
|-
 
|-
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|01:32  
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|'''function space function underscore name'''
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−
 
+
−
|-
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| 01.32  
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|within curly brackets,  
 
|within curly brackets,  
  
 
|-
 
|-
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|01:34
 
|the '''commands''' to be executed.
 
|the '''commands''' to be executed.
  
 
|-
 
|-
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|01:37
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| The second syntax is-
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|The second syntax is-
  
 
|-
 
|-
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|01:39
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|'''function underscore name open and close round brackets'''
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|'''function_name open and close round brackets'''
  
 
|-
 
|-
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|01:42
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|within curly barckets,  
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|within curly brackets,  
  
 
|-
 
|-
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|01:44
 
|the '''commands''' to be executed.
 
|the '''commands''' to be executed.
  
 
|-
 
|-
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|01:47
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| '''Function call'''-
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| '''Function call'''-'''Function''' can be called anywhere within the program.
  
 
|-
 
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|01:53
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|'''Function''' can be called anywhere within the program.
+
−
 
+
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|-
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|Type the '''function name '''at the location where you want to call it.
 
|Type the '''function name '''at the location where you want to call it.
  
 
|-
 
|-
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|  01:58
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|The syntax is the''' function name '''itself.
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|The syntax is the''' function_name '''itself.
  
 
|-
 
|-
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| 02:02
 
| Let us understand this with the help of a simple example.
 
| Let us understand this with the help of a simple example.
  
 
|-
 
|-
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| 02:07
 
| I have already typed the code in a file '''function.sh'''.  
 
| I have already typed the code in a file '''function.sh'''.  
  
 
|-
 
|-
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| 02:12
 
| This is the''' shebang line'''.
 
| This is the''' shebang line'''.
  
 
|-
 
|-
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| 02:14
 
| '''Function''' is declared by the keyword '''function''' followed by '''function name'''.  
 
| '''Function''' is declared by the keyword '''function''' followed by '''function name'''.  
  
 
|-
 
|-
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|Here, '''function name''' is '''machine'''.
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|Here, the '''function name''' is '''machine'''.
  
 
|-
 
|-
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| 02:26
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| The content within curly brackets is called '''function definition'''.
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| The contents within curly brackets is called '''function definition'''.
  
 
|-
 
|-
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|  02:32
 
|I have displayed various machine details like-
 
|I have displayed various machine details like-
  
 
|-
 
|-
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|  02:36
 
|'''uname hyphen a '''gives machine information.
 
|'''uname hyphen a '''gives machine information.
  
 
|-
 
|-
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|  02.41
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|  02:41
 
|'''w hyphen h '''gives users logged onto system.
 
|'''w hyphen h '''gives users logged onto system.
  
 
|-
 
|-
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|  02.46
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|  02:46
 
|'''uptime '''gives the time since machine was on.
 
|'''uptime '''gives the time since machine was on.
  
 
|-
 
|-
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|  02.51
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|  02:51
 
|'''free''' gives memory status.
 
|'''free''' gives memory status.
  
 
|-
 
|-
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|  02:54
 
|'''df hyphen h''' gives filesystem status.
 
|'''df hyphen h''' gives filesystem status.
  
 
|-
 
|-
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| 02:57
 
| The main program starts here.  
 
| The main program starts here.  
  
 
|-
 
|-
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|03.01   
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|03:01   
 
|We display the message ''' “Beginning of main program” '''.
 
|We display the message ''' “Beginning of main program” '''.
  
 
|-
 
|-
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| 03.06
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| 03:06
 
| Here,''' machine '''is a '''function call. '''
 
| Here,''' machine '''is a '''function call. '''
  
 
|-
 
|-
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| 03:09
 
| Then we display the message '''“End of main program”'''.
 
| Then we display the message '''“End of main program”'''.
  
 
|-
 
|-
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| 03.13
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| 03:13
 
| Let us understand the workflow.
 
| Let us understand the workflow.
  
 
|-
 
|-
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|  03:16
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|# When the '''bash interpreter''' visits the '''function definition''', it simply scans the '''function.'''
+
|When the '''bash interpreter''' visits the '''function definition''', it simply scans the '''function.'''
  
 
|-
 
|-
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|  03:23
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|# The '''function''' is called only when its name appears within the script.
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|The '''function''' is called only when its name appears within the script.
  
 
|-
 
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|03:28
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|# When the '''interpreter''' reads the '''function name''', it executes the '''function definition.'''  
+
| When the '''interpreter''' reads the '''function name''', it executes the '''function definition.'''  
  
 
|-
 
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|03:36
 
| The '''interpreter''' treats '''function name '''as a command.
 
| The '''interpreter''' treats '''function name '''as a command.
 
|-
 
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| 03.41
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|03:41
 
|Please remember that we have to '''define''' the '''function''' before '''calling''' it.
 
|Please remember that we have to '''define''' the '''function''' before '''calling''' it.
  
 
|-
 
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| 03.47
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| 03:47
 
| Now go to the''' terminal.''' To make this code file'' ''executable,
 
| Now go to the''' terminal.''' To make this code file'' ''executable,
  
 
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|type: '''chmod space plus x space function dot sh'''
 
|type: '''chmod space plus x space function dot sh'''
  
 
|-
 
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|  03:59
 
|Press '''Enter.'''
 
|Press '''Enter.'''
  
 
|-
 
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| 04:01
 
|  Type: '''dot slash function dot sh'''  
 
|  Type: '''dot slash function dot sh'''  
  
 
|-
 
|-
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|  04:05
 
|Press '''Enter.'''
 
|Press '''Enter.'''
  
 
|-
 
|-
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| 04.07
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| 04:07
 
| The '''output''' that is the machine details of my system are seen on the '''terminal.'''
 
| The '''output''' that is the machine details of my system are seen on the '''terminal.'''
  
 
|-
 
|-
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|  04.14
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|  04:14
 
|Please Note: The '''output''' will vary from system to system.
 
|Please Note: The '''output''' will vary from system to system.
  
 
|-
 
|-
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|  04.19
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|  04:19
 
|This brings us to the end of this tutorial.
 
|This brings us to the end of this tutorial.
  
 
|-
 
|-
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|  04.22
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|  04:22
 
|Come back to our '''slides'''.
 
|Come back to our '''slides'''.
  
 
|-
 
|-
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| 04.24
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| 04:24
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| Let us summarize.  
+
| Let us summarize. In this tutorial, we learned:
  
 
|-
 
|-
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|  04.25
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|  04:28
−
|In this tutorial, we learned:
+
|Importance of '''functions'''
  
 
|-
 
|-
−
| 04.28
+
|04:30
−
|* Importance of '''functions'''
+
|'''Function declaration'''
−
|-
+
−
|  04.30
+
−
|* '''Function declaration'''
+
  
 
|-
 
|-
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| 04.32
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|04:32
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|* '''Function call'''
+
|'''Function call''' Work flow of '''function'''
  
 
|-
 
|-
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|  04.33
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|  04:35
−
|* Work flow of '''function'''
+
−
 
+
−
|-
+
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|  04.35
+
 
| with an example.
 
| with an example.
  
 
|-
 
|-
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| 04.37
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| 04:37
−
| As an assignment-
+
| As an assignment-write a program with two functions.
−
 
+
−
|-
+
−
|  04.38
+
−
|write a program with two functions.
+
  
 
|-
 
|-
−
|  04.42
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|  04:42
−
|# The first function should display the disks-pace usage in human readable form '''(Hint: df hyphen h)'''.
+
|The first function should display the disk-space usage in human readable form (Hint: df hyphen h).
  
 
|-
 
|-
−
| 04.51
+
|04:51
−
|# The second function should display filesystem usage in human readable form '''(Hint: du hyphen h)'''.
+
|The second function should display filesystem usage in human readable form (Hint: du hyphen h).
  
 
|-
 
|-
−
| 05.00
+
| 05:00
 
| Watch the video available at the link shown below.
 
| Watch the video available at the link shown below.
  
 
|-
 
|-
−
|  05.03
+
|  05:03
 
|It summarizes the Spoken-Tutorial project.
 
|It summarizes the Spoken-Tutorial project.
  
 
|-
 
|-
−
|  05.07
+
|  05:07
 
|If you do not have good bandwidth, you can download and watch it.
 
|If you do not have good bandwidth, you can download and watch it.
  
 
|-
 
|-
−
|  05.12
+
|  05:12
 
| The Spoken Tutorial Project team: Conducts workshops using spoken tutorials;
 
| The Spoken Tutorial Project team: Conducts workshops using spoken tutorials;
  
 
|-
 
|-
−
|  05.17
+
|  05:17
 
|Gives certificates to those who pass an online test.
 
|Gives certificates to those who pass an online test.
  
 
|-
 
|-
−
|  05.21
+
|  05:21
 
|For more details, please write to contact@spoken-tutorial.org
 
|For more details, please write to contact@spoken-tutorial.org
  
 
|-
 
|-
−
|  05.29
+
|  05:29
 
| '''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.
  
 
|-
 
|-
−
| 05.33  
+
| 05:33  
 
|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.
  
 
|-
 
|-
−
|  05.41
+
|  05:41
−
|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
  
 
|-
 
|-
−
|  05.47
+
|  05:47
 
| The script has been contributed by FOSSEE and spoken-tutorial team.
 
| The script has been contributed by FOSSEE and spoken-tutorial team.
  
 
|-
 
|-
−
|  05.52
+
|  05:52
 
|This is Ashwini Patil from IIT Bombay, signing off.
 
|This is Ashwini Patil from IIT Bombay, signing off.
  
 
|-
 
|-
−
|  05.56
+
|  05:56
 
|Thank you for joining.
 
|Thank you for joining.
  
 
|}
 
|}

Latest revision as of 17:08, 23 March 2017

Time Narration
00:01 Dear friends, welcome to the spoken tutorial on Basics of functions in Bash.
00:08 In this tutorial, we will learn:
00:11 Importance of Functions
00:13 To declare a function
00:15 To call a function
00:17 Work flow of a function
00:19 with the help of an example.
00:22 To follow this tutorial, you should have knowledge of Shell Scripting in BASH.
00:28 If not, for relevant tutorials, please visit our website which is as shown. http://www.spoken-tutorial.org
00:34 For this tutorial, I am using Ubuntu Linux 12.04 Operating System.
00:40 Till now we were using GNU BASH version 4.1.10
00:46 From now onwards, we will use GNU BASH version 4.2
00:52 Please note, GNU Bash version 4 or above is recommended for practice.
00:58 Let us see what is a function and its usage.
01:03 A function is a collection of commands or an algorithm.
01:08 It is intended to do a specific task.
01:12 It is used to break-up a complex program into separate tasks.
01:18 This improves overall script readability and ease of use.
01:24 There are two syntaxes for function declaration.
01:28 First syntax is-function space function_name
01:32 within curly brackets,
01:34 the commands to be executed.
01:37 The second syntax is-
01:39 function_name open and close round brackets
01:42 within curly brackets,
01:44 the commands to be executed.
01:47 Function call-Function can be called anywhere within the program.
01:53 Type the function name at the location where you want to call it.
01:58 The syntax is the function_name itself.
02:02 Let us understand this with the help of a simple example.
02:07 I have already typed the code in a file function.sh.
02:12 This is the shebang line.
02:14 Function is declared by the keyword function followed by function name.
02:21 Here, the function name is machine.
02:26 The contents within curly brackets is called function definition.
02:32 I have displayed various machine details like-
02:36 uname hyphen a gives machine information.
02:41 w hyphen h gives users logged onto system.
02:46 uptime gives the time since machine was on.
02:51 free gives memory status.
02:54 df hyphen h gives filesystem status.
02:57 The main program starts here.
03:01 We display the message “Beginning of main program” .
03:06 Here, machine is a function call.
03:09 Then we display the message “End of main program”.
03:13 Let us understand the workflow.
03:16 When the bash interpreter visits the function definition, it simply scans the function.
03:23 The function is called only when its name appears within the script.
03:28 When the interpreter reads the function name, it executes the function definition.
03:36 The interpreter treats function name as a command.
03:41 Please remember that we have to define the function before calling it.
03:47 Now go to the terminal. To make this code file executable,
03:52 type: chmod space plus x space function dot sh
03:59 Press Enter.
04:01 Type: dot slash function dot sh
04:05 Press Enter.
04:07 The output that is the machine details of my system are seen on the terminal.
04:14 Please Note: The output will vary from system to system.
04:19 This brings us to the end of this tutorial.
04:22 Come back to our slides.
04:24 Let us summarize. In this tutorial, we learned:
04:28 Importance of functions
04:30 Function declaration
04:32 Function call Work flow of function
04:35 with an example.
04:37 As an assignment-write a program with two functions.
04:42 The first function should display the disk-space usage in human readable form (Hint: df hyphen h).
04:51 The second function should display filesystem usage in human readable form (Hint: du hyphen h).
05:00 Watch the video available at the link shown below.
05:03 It summarizes the Spoken-Tutorial project.
05:07 If you do not have good bandwidth, you can download and watch it.
05:12 The Spoken Tutorial Project team: Conducts workshops using spoken tutorials;
05:17 Gives certificates to those who pass an online test.
05:21 For more details, please write to contact@spoken-tutorial.org
05:29 Spoken Tutorial Project is a part of the Talk to a Teacher project.
05:33 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
05:41 More information on this mission is available at the link shown below: http://spoken-tutorial.org/NMEICT-Intro
05:47 The script has been contributed by FOSSEE and spoken-tutorial team.
05:52 This is Ashwini Patil from IIT Bombay, signing off.
05:56 Thank you for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14

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