BASH/C3/More-on-functions/English-timed

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	$(Dollar)1 is the first positional parameter.
01:22	$(Dollar)2 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 and 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 will 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