Difference between revisions of "BASH/C3/Arrays-and-functions/English-timed"
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| − | | | + | |'''GNU BASH''' version 4.2 |
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Latest revision as of 17:12, 23 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. |
