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

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For more details, please write to contact@spoken-tutorial.org
 
For more details, please write to contact@spoken-tutorial.org
  

Revision as of 15:46, 7 March 2017

Time Narration
00:01 Dear friends, welcome to the spoken tutorial on Arrays & functions.
00:07 In this tutorial, we will learn:
00:11 * To pass an array to a function
00:14 * Use of exit statement in a function
00:17 * Use of return statement in a function
00:20 with the help of some examples.
00:24 To follow this tutorial, you should have knowledge of Shell Scripting.
00:29 You should also have knowledge of arrays and 'if' statement in BASH.
00:36 If not, for relevant tutorials, please visit our website which is as shown. http://www.spoken-tutorial.org
00:43 For this tutorial, I am using:
00:46 * Ubuntu Linux 12.04 Operating System and
00:50 * GNU BASH version 4.2
00:54 Please note, GNU Bash version 4 or above is recommended to practice this tutorial.
01:02 Let us first learn how to pass an array to a function and its usage.
01:09 Let me open a file function_(underscore)array dot sh.
01:15 This is the shebang line.
01:18 Our function name is array_(underscore) display.
01:22 Open curly brace opens the function definition.
01:27 The use of Dollar @(at-sign) was explained in previous tutorials in this series.
01:34 Basically, it is used to print all arguments passed to a function.
01:40 Dollar @ (at sign) within round brackets stores array elements in variable 'array'.
01:47 Dollar opening curly brace array within square bracket @(At-sign) closing curly brace.
01:55 This line of code displays all the elements of an array.
02:00 Dollar opening curly brace array within square brackets one closing curly brace.
02:08 This line of code displays the second element of the array.
02:14 operating_systems is declared with the elements "Ubuntu", "Fedora", "Redhat" and "Suse".
02:22 Here, array operating_systems is passed to the function array_display.
02:29 The syntax to pass an array to a function is function_name space dollar opening curly brace array_name within square brackets @(At sign) closing curly brace.
02:45 Come back to our program.
02:48 Similarly, colors is declared with the elements White, green, red and blue.
02:57 Here, array colors is passed to the function array_display.
03:02 Now let's save the file and go to the terminal.
03:07 Type: chmod space plus x space function underscore array dot sh
03:18 Press Enter.Type: dot slash function underscore array dot sh
03:25 Press Enter.
03:27 As we can see, array elements of 'operating_systems' and 'colors' are displayed.
03:33 And the second array element of 'operating_systems' and 'colors' are also displayed.
03:41 In Bash, 'exit' and 'return' statements give status code of a function or a program.
03:49 The return statement will return to the script from where it was called.
03:54 exit statement will end the entire script from where it is encountered.
04:01 Let us learn these 2 ways to return within a function.
04:06 Let me open a file 'return_exit.sh'.
04:12 This is the shebang line.
04:14 Function name is return_(Underscore)function .
04:18 Open curly brace opens the function definition.
04:22 This if statement compares two variables.
04:27 If the two variables are equal then commands in 'if' are executed.
04:33 This echo statement displays the message:
04:36 "This is return function".
04:39 return 0 moves the control from function to main program with status code 0(zero).
04:47 Note that the statements after return will not be executed in a function.
04:54 'fi' indicates the end of 'if' statement.
04:58 Here the function name is exit_(Underscore)function.
05:02 The 'if' statement here, compares two variables.
05:06 If the two variables are equal then the commands in 'if' are executed.
05:14 This echo statement displays the message "This is exit function" .
05:19 exit 0 will terminate the program.
05:23 'fi' indicates the end of this 'if' statement.
05:27 This is a function call with arguments 3 and 3.
05:33 This displays the message "We are in main program".
05:38 This is another function call with arguments 3 and 3.
05:44 This echo statement displays the message "This line is not displayed".
05:49 Note that exit will terminate the program.
05:53 Anything after exit will not be executed.
05:58 Save the file and go to the terminal.
06:00 Type: chmod space plus x space return underscore exit dot sh
06:09 Press Enter.
06:12 Type: dot slash return underscore exit dot sh
06:18 Press Enter.
06:20 The output displays the messages as shown.
06:24 Now, let us understand the flow of the program.
06:27 The control will be in main program which is the script itself.
06:33 The control goes to return_function because of the function call.
06:39 As the two variables are equal, it displays the message "This is return function".
06:47 Then it encounters return 0. And the control flows from function to the statement below the function call, in the main program.
06:59 Then it displays the message "We are in main program" .
07:03 After that, the control goes to exit_function because of the function call.
07:11 As the two variables are equal, it displays the message "This is exit function".
07:19 Then it encounters exit 0. This will terminate the program.
07:25 Any statement after exit will not be executed.
07:30 Also, the statement "This line is not displayed" will not be executed.
07:36 Hope the difference is clear to you.
07:39 Let us now summarize.
07:41 In this tutorial, we learnt:
07:44 * To pass an array to a function
07:47 * Use of exit statement in a function
07:50 * Use of return statement in a function
07:53 with the help of some examples.
07:56 As an assignment-Write a program
07:58 where a function adds all the elements in an array. The function should display the sum of elements.
08:07 Make 2 function calls with array elements (1, 2, 3) and (4, 5, 6).
08:15 Watch the video available at the link shown below. http://spoken-tutorial.org/What_is_a_Spoken_Tutorial
08:19 It summarizes the Spoken Tutorial project.
08:23 If you do not have good bandwidth, you can download and watch it.
08:28 The Spoken Tutorial Project Team:
08:30 Conducts workshops using spoken tutorials.Gives certificates to those who pass an online test.

For more details, please write to contact@spoken-tutorial.org

08:45 Spoken Tutorial Project is a part of the Talk to a Teacher project.
08:49 It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this mission is available at the link shown below. http://spoken-tutorial.org/NMEICT-Intro
09:04 The script has been contributed by FOSSEE and Spoken-Tutorial teams.
09:10 This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

Pratik kamble, Sandhya.np14