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

Timee	Narration
00:01	Dear friends, Welcome to the spoken tutorial on More on redirection
00:07	In this tutorial, we will learn Redirection of both standard error and output
00:13	Appending redirected output
00:15	With the help of some examples
00:19	To follow this tutorial you should have knowledge of Shell Scripting in BASH.
00:25	If not, for relevant tutorials please visit our website which is as shown http://www.spoken-tutorial.org
00:30	For this tutorial I am using Ubuntu Linux 12.04 Operating System
00:35	GNU BASH version 4.2
00:39	Please note, GNU Bash version 4 or above is recommended for practice.
00:46	In an earlier tutorial, we learned about standard output and standard errors.
00:52	Both stderr as well as the stdout can be redirected to the same file.
00:58	This can be done in multiple ways.
01:01	We will cover two of the most important methods of redirections in this tutorial.
01:08	The first method to redirect both the standard output and error is by using &>(ampersand) followed by greater-than sign
01:18	The syntax is Command space ampersand greater than space filename
01:25	Let me open a file named redirect.sh.
01:30	I have typed some code in this file.
01:32	This is the shebang line.
01:36	ls lists the directory content of 2 directories namely /usr and /user
01:44	Note that /user directory does not exist.
01:48	Hence the command ls will throw an error.
01:52	&(ampersand) followed by greater than will redirect stdout and stderr to out_(underscore)file.txt
02:03	Now Save the file.
02:05	Let us run the file redirect.sh.
02:07	Open the terminal using CTRL+ALT+T keys simultaneously on your keyboard
02:15	Type chmod space plus x space redirect dot sh
02:23	Press Enter
02:25	Type dot slash redirect dot sh
02:28	Press Enter.
02:30	We can see the output by opening out_(underscore)file.(dot)txt
02:36	Type cat space out_(underscore)file.(dot)txt
02:42	We can see both the error and output.
02:48	The error for directory /user is recorded in this file.
02:51	It says that there was no '/user' directory found.
02:56	The directory content for /usr is displayed.
03:00	Please note that the content for '/usr' directory may vary on your system.
03:06	Now let us delete this file. So, on the terminal Type rm space out_(underscore)file. (dot)txt
03:15	Another method is to use 2 greater than ampersand 1 after the filename
03:24	The syntax is command space greater than filename space 2 greater than ampersand 1
03:33	We can also redirect to slash dev slash null (/dev/null) file.
03:39	Let us learn a little more about slash dev slash null (/dev/null) file.
03:45	It is a special kind of file
03:48	It is a null file or a place where we can dump anything.
03:52	It includes the output and error messages
03:57	It is also called as bit bucket.
04:00	Let us now come back to our code in gedit.
04:04	Let us redirect both standard output and error to the null file.
04:11	I will copy this line of code and paste it below over here.
04:16	I want both the output and error messages to be discarded.
04:21	So I will change this part of the copied code.> (greater than) means truncate or write.
04:30	slash dev slash null is the null file 2>&1 (2 greater than ampersand 1)
04:37	Number “2” will redirect standard error to standard output, denoted by number “1”.
04:45	Now click on Save. Save the code.
04:48	Let us run the file redirect.sh.
04:52	Go to the terminal.
04:54	Recall the previous command with the up-arrow key. dot slash redirect.sh and press Enter.
05:03	We can see the output by typing cat out_(underscore)file.(dot)txt
05:11	Come back to our slides.
05:15	* We can capture as well as append standard output or error to a file.
05:21	The output or the error will be appended at the end of the file.
05:26	If the file does not exist, it will create a new file.
05:31	The syntax is command space greater than greater than space followed by filename
05:41	Let us understand this using an example.
05:45	Let me open the file redirect.(dot)sh
05:49	Now, here let's Type date space greater than greater than space out_(underscore)file.(dot)txt
06:00	The 'date' command will simply display the system date as output.
06:06	We can check this command on the terminal by typing 'date.'
06:11	Come back to the terminal.Type date You can see that the system date i.e. the current date is displayed.
06:23	The output of date command will be appended to the out_(underscore)file.(dot)txt file.
06:31	We are using this file to capture standard output and error of ls command.
06:39	Click on Save
06:40	Switch to the terminal.
06:43	Now press the uparrow key.Recall the previous command dot slash redirect dot sh
06:50	and press Enter.
06:52	Let us check the output by opening out_(underscore) file.(dot)txt
06:59	Type cat space out_(underscore)file.(dot)txt
07:05	Observe that the output of 'date' command is appended to the end of the file.
07:12	This brings us to the end of this tutorial.
07:15	Let us summarise.
07:17	In this tutorial we learnt
07:19	Redirection of both standard error and output And to append the redirected output
07:27	As an assignment,
07:29	Create X_(underscore)file.(dot)txt file with some content.
07:34	Redirect the content of both out_(underscore)file.(dot)txt and X_(underscore)file.(dot)txt to a new file.
07:44	Watch the video available at the link shown below.
07:47	It summarises the Spoken Tutorial project.
07:51	If you do not have good bandwidth, you can download and watch it.
07:56	The Spoken Tutorial Project Team Conducts workshops using spoken tutorials Gives certificates to those who pass an online test
08:06	For more details, please write to contact@spoken-tutorial.org
08:13	Spoken Tutorial Project is a part of the Talk to a Teacher project.
08:17	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
08:30	The script has been contributed by FOSSEE and Spoken-Tutorial teams.
08:37	This is Ashwini from IIT Bombay.Thank you for joining.

Contributors and Content Editors

Pratik kamble, Sandhya.np14