BASH/C3/Advance-topics-in-a-function/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Dear friends, welcome to the spoken tutorial onAdvance topics in a function . |
| 00:08 | In this tutorial, we will learn: |
| 00:11 | source command To put a function in the background |
| 00:14 | with the help of some examples. |
| 00:18 | To follow this tutorial, you should have knowledge of Shell Scripting in BASH. |
| 00:24 | If not, for relevant tutorials, please visit our website which is as shown. http://spoken-tutorial.org/What_is_a_Spoken_Tutorial |
| 00:30 | For this tutorial, I am using: |
| 00:32 | Ubuntu Linux 12.04 Operating System and |
| 00:36 | GNU BASH version 4.2 |
| 00:40 | Please note, GNU Bash version 4 or above is recommended for practice. |
| 00:46 | source command is used to load a file into Shell script. |
| 00:53 | It reads and executes commands from that file. |
| 00:58 | It also imports code into the script. |
| 01:01 | This is useful when multiple scripts use a common data or a function library. |
| 01:09 | The syntax for source command is as follows- |
| 01:12 | source filename |
| 01:15 | source Path_to_file |
| 01:18 | souce filename arguments. |
| 01:22 | Let me open a file 'function dot sh'. |
| 01:26 | This is theshebang line. |
| 01:29 | source detail dot sh will load the file detail dot sh into function dot sh. |
| 01:37 | Let me open detail dot sh file. |
| 01:41 | I have a function machine. |
| 01:44 | Now, type inside the function- |
| 01:47 | echo "function machine is called in function dot sh file" . |
| 01:52 | Click on Save. |
| 01:54 | Now let us go back to function dot sh file. |
| 01:59 | Here, type: echo “Beginning of program”. |
| 02:04 | Click on Save. |
| 02:06 | Then type: machine echo “End of program”. |
| 02:12 | This will print the message “Beginning of program”. |
| 02:16 | machine is the function call. |
| 02:19 | And this will print the message End of program. |
| 02:23 | Note that machine is the function which we created in the detail dot sh file. |
| 02:29 | And we are calling the function, here, in function dot sh file. |
| 02:34 | Now click on Save. |
| 02:36 | Let us execute the program. |
| 02:41 | So, type on the terminal: chmod space plus (+) x space function dot sh |
| 02:51 | Press Enter. |
| 02:53 | Type: dot slash function dot sh |
| 02:56 | Press Enter. |
| 02:59 | The output is displayed. |
| 03:02 | Now let's move on to background function. |
| 03:06 | To run a process in the background, we use & (ampersand) at the end of a function call. |
| 03:13 | The shell forks a child process to run the command. |
| 03:19 | The forked process will have a job number and a PID (Process Identifier). |
| 03:27 | Let us understand this with the help of an example. I will open the file background dot sh. |
| 03:35 | This is the shebang line. |
| 03:38 | bg underscore function marks the beginning of the function. |
| 03:44 | The echo statement here displays the message "Inside bg_function”. |
| 03:50 | Next, we will use the find command to find all the dotmp3 files. |
| 03:57 | This statement will find all the files with the extension dot mp3. |
| 04:03 | It will do so in the current working directory. |
| 04:07 | Hyphen iname is used to ignore the case. |
| 04:11 | And the result is stored in myplaylist.txt. |
| 04:16 | Now, type: bg underscore function ampersand(&). This is the function call. '&'(Ampersand) puts 'bg_function' in the background. |
| 04:28 | Now click on Save. |
| 04:31 | Let us execute the program. |
| 04:34 | Come back to the terminal. |
| 04:37 | Type: chmod space plus x space background dot sh |
| 04:45 | Press Enter.Now, type: dot slash background dot sh |
| 04:51 | Press Enter. |
| 04:53 | Blank output indicates dot mp3 file is not present in current directory. |
| 05:02 | Now, come back to our program. |
| 05:05 | Type: echo (hyphen) -e "Process running in background are: backslash n" and jobs space hyphen l |
| 05:19 | Click on Save. |
| 05:21 | This echo statement will display the message “Process running in background are ”. |
| 05:28 | jobs space hyphen l lists the status of all background jobs. |
| 05:34 | Now come back to our terminal. |
| 05:38 | Now, type: dot slash background.sh. |
| 05:42 | Press Enter. |
| 05:44 | The output is shown. |
| 05:48 | Here, one within opening and closing square bracket is the job number. |
| 05:53 | 3962 is the PID. |
| 05:57 | PID will vary accordingly. |
| 06:01 | If the function takes time to execute, it will run the process in the background |
| 06:06 | and we will see the status as "Running". |
| 06:11 | If the function gets executed before the script, we will see the status as "Done". |
| 06:20 | The output will vary from machine to machine. |
| 06:23 | This brings us to the end of this tutorial. |
| 06:28 | Let us summarize.In this tutorial, we learned: |
| 06:32 | Source command |
| 06:34 | To put a function in the background |
| 06:36 | with the help of some examples. |
| 06:39 | As an assignment:Write a function add to add two numbers and call the function in another file. |
| 06:47 | Watch the video available at the link shown below http://spoken-tutorial.org/What_is_a_Spoken_Tutorial |
| 06:51 | It summarizes the Spoken-Tutorial project. |
| 06:55 | If you do not have good bandwidth, you can download and watch it. |
| 07:00 | The Spoken Tutorial Project team: Conducts workshops using spoken tutorials. Gives certificates to those who pass an online test. |
| 07:10 | For more details, please write to contact@spoken-tutorial.org |
| 07:18 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
| 07:22 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 07:30 | More information on this mission is available at the link shown below. http://spoken-tutorial.org/NMEICT-Intro |
| 07:36 | The script has been contributed by FOSSEE and Spoken-Tutorial teams. |
| 07:42 | This is Ashwini from IIT Bombay. Thank you for joining. |
