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

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|If not, for relevant tutorials, please visit our website which is as shown: '''(http://www.spoken-tutorial.org)'''
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|'''$(Dollar)2 '''is the second '''positional parameter'''.
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| In a similar manner, I will '''call''' the same '''function''' with a different set of '''arguments'''. So, I have'''say_welcome''' space within double quotes '''functions in''' space and within double quotes '''Bash'''.
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| In a similar manner, I will '''call''' the same '''function''' with a different set of '''arguments'''. So, I have'''say_welcome''' space within double quotes '''functions in''' space within double quotes '''Bash'''.
  
 
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| Dollar 1($1) was substituted by the '''string''' "Bash" and Dollar 2($2) with "learning".
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| Dollar 1 ($1) was substituted by the '''string''' "Bash" and Dollar 2 ($2) with "learning".
  
 
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| Then again, Dollar 1($1) was substituted by "functions in" and Dollar 2($2) with "Bash".
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| Its value will be valid within the '''function''' in which it is defined.
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| '''Local variables''' are declared using keyword '''local'''.
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|* '''Local variables''' are declared using keyword '''local'''.
  
 
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| Let me open a file named '''function_(underscore)local.sh''''.
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|So, the '''variable last_name '''can be accessed throughout the '''script'''.
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| Now, here the variable '''middle_name ''' is declared without keyword. So, its value will be '''global ''' throughout the script.
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| Now, here, the variable '''middle_name ''' is declared without keyword. So, its value will be '''global ''' throughout the script.
  
 
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| Once again, we will '''call''' the '''function '''here.
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| Once again, we '''call''' the '''function '''here.
  
 
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| We pass two '''arguments''' to this''' function call''', namely- “Pratik” and  “Patil”.
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| We pass two '''arguments''' to this''' function call''' namely- “Pratik” and  “Patil”.
  
 
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| These '''echo statements''' will display the value of '''variables'''
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| These '''echo''' statements will display the value of '''variables'''-
  
 
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| Please keep in mind that '''variable first_name '''is a '''local variable.'''
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| Please keep in mind that variable '''first_name '''is a '''local variable.'''
  
 
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| The first line of output displays the message '''Hello Pratik K Patil.'''
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| The first line of output displays the message '''"Hello Pratik K Patil".'''
  
 
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|* To pass '''arguments''' to a''' function ''';
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|* To pass '''arguments''' to a''' function''';
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* To declare '''Local variable '''in a '''function''';
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* To declare '''local variable '''in a '''function''';
  
 
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|* To declare '''Global variable '''in a '''function''' with the help of a few examples.
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|* To declare '''global variable '''in a '''function''' with the help of a few examples.
  
 
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|It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro
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|It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this mission is available at: http://spoken-tutorial.org/NMEICT-Intro
  
 
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Revision as of 10:59, 14 July 2015

Time Narration
00:01 Welcome to the spoken tutorial on More on functions.
00:06 In this tutorial, we will learn:
00:09 * To pass an argument to a function;
00:11 * To define local variable within a function and
00:16 * To define global variable in a function
00:19 with the help of some examples.
00:23 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)
00:35 For this tutorial, I am using:
00:37 * Ubuntu Linux 12.04 Operating System
00:42 * GNU BASH version 4.2.
00:45 Please note, GNU Bash version 4 or above is recommended to practice this tutorial.
00:52 Let us first learn how to pass an argument to a function and its usage.
00:59 Let me open a file 'function_(underscore) parameters.sh' .
01:05 This is the shebang line.
01:08 Our function name is say_(underscore)welcome.
01:13 Open curly bracket opens the function definition.
01:18 '$1' (Dollar one) is the first positional parameter.
01:22 '$2' (Dollar two) is the second positional parameter.
01:26 Close curly bracket closes the function definition.
01:30 Here, the function 'say_welcome' is called with arguments.
01:35 The syntax is- function name i.e. "say_welcome" followed by the arguments within double quotes, i.e. "Bash" and "learning".
01:49 In a similar manner, I will call the same function with a different set of arguments. So, I havesay_welcome space within double quotes functions in space within double quotes Bash.
02:05 Save the file and go to the terminal.
02:08 Type: chmod space plus x space function underscore parameters dot sh.
02:17 Press Enter.
02:19 Type: dot slash function underscore parameters dot sh.
02:26 Press Enter.
02:28 We see that the positional parameters were substituted by the arguments passed to a function.
02:36 Dollar 1 ($1) was substituted by the string "Bash" and Dollar 2 ($2) with "learning".
02:45 Then again, Dollar 1 ($1) was substituted by "functions in" and Dollar 2 ($2) with "Bash".
02:55 In Bash, variables can be declared as local variables and global variables.
03:01 Local variable:
03:03 * Its value will be valid within the function in which it is defined.
03:10 * Local variables are declared using keyword local.
03:15 Global variable:
03:17 The value of a global variable can be accessed throughout a Bash script.
03:24 Let us learn these 2 ways to declare a variable within a function.
03:29 Let me open a file named 'function_(underscore)local.sh'.
03:35 This is the shebang line.
03:39 Function name is say_(underscore) hello.
03:43 Here, variable first_name is declared with keyword local
03:49 which means its value will be valid within the function say_hello only.
03:55 A variable declared without any keyword is treated as a global variable.
04:01 So, the variable last_name can be accessed throughout the script.
04:08 In this echo line, we will display the value of variables
04:12 first_name,
04:14 middle_name
04:15 and last_name.
04:17 After this, we close the function.
04:21 Now, here, the variable middle_name is declared without keyword. So, its value will be global throughout the script.
04:30 Once again, we call the function here.
04:34 We pass two arguments to this function call namely- “Pratik” and “Patil”.
04:41 These echo statements will display the value of variables-
04:45 $first_name,
04:46 $middle_name and $last_name.
04:51 Please keep in mind that variable first_name is a local variable.
04:57 Save the file and go to the terminal.
05:00 Type: chmod space plus x space function underscore local dot sh.
05:09 Press Enter.
05:11 Type: dot slash function underscore local dot sh
05:16 Press Enter.
05:18 The first line of output displays the message "Hello Pratik K Patil".
05:25 Here, the variable first_name that contains value "Pratik" is local
05:31 which means the value is limited to the function.
05:35 Now, let us see how the local variable behaves outside the function.
05:41 Here, nothing is displayed in first_name.
05:44 This is because the value of first_name is local to the function. And it is not available outside the function.
05:53 middle_name and last_name are printed as they are global variables.
05:59 Hope the difference is clear to you.
06:02 Let us now summarize.
06:04 In this tutorial, we learned:
06:07 * To pass arguments to a function;
  • To declare local variable in a function;
06:14 * To declare global variable in a function with the help of a few examples.
06:20 As an assignment-
06:22 write a program
06:23 where the function accepts two arguments. The function should multiply the two arguments.
06:31 Make 3 function calls with arguments (1, 2), (2, 3) and (3, 4).
06:39 Watch the video available at the link shown below.
06:43 It summarizes the Spoken-Tutorial project. If you do not have good bandwidth, you can download and watch it.
06:51 The Spoken Tutorial Project team:
  • Conducts workshops using spoken tutorials;
  • Gives certificates to those who pass an online test.
07:00 For more details, please write to contact@spoken-tutorial.org
07:07 Spoken Tutorial project is a part of the Talk to a Teacher project.
07:11 It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this mission is available at: http://spoken-tutorial.org/NMEICT-Intro
07:26 The script has been contributed by FOSSEE and Spoken-Tutorial teams.
07:31 This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

Pratik kamble, Sandhya.np14

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