BOSS-Linux/C3/The-sed-command/English-timed

Time	Narration
00:01	Welcome to this spoken tutorial on sed - the stream editor.
00:07	In this tutorial, we will learn usage of sed command.
00:11	We will do through some examples.
00:14	To record this tutorial,
00:16	I am using Linux Operating System and GNU BASH version 4.2.24
00:26	Please note, GNU bash version 4 or above is recommended to practice this tutorial.
00:33	As prerequisites,
00:35	you should know basics of Linux terminal.
00:38	For relevant tutorials, please visit our website which is as shown: http://spoken-tutorial.org
00:44	Let us start with an introduction to sed.
00:47	sed is a stream editor.
00:50	sed finds some pattern of text in a particular location of a file.
00:57	It performs some display or editing function-
01:01	editing functions like insertion, substitution and deletion in matched text.
01:10	Let us start with some examples.
01:13	We will see how to print using the sed command.
01:18	I have a file called seddemo.txt in the home directory.
01:23	Let us view its contents.
01:26	In this file, we have some entries like- roll no, name, stream, marks, pass or fail and the stipend amount.
01:38	Now suppose, we want to print the second line of the file.
01:43	For this, we need to open the terminal.
01:47	Now, type:sed space within single quotes 2p after the single quotes space seddemo.txt
01:57	Press Enter.
02:00	Here, 2 denotes the location which is the second line.
02:05	'p' denotes the action which is printing.
02:09	Now look at the output.
02:11	It shows the entire file but see that the second line is printed twice.
02:18	This is the default behavior of action p.
02:22	To only print the second line,
02:25	type: sed space -n space (within single quotes) 2p after the single quotes space seddemo.txt
02:37	Press Enter.
02:40	We see only the second line is printed.
02:44	-n stands for ‘silent mode’ which will suppress all unnecessary output.
02:51	Then we give the location in the stream that we want to edit or display.
02:57	We want to select the second line.
03:00	p indicates the action we want to take i.e. to print the second line
03:06	and seddemo.txt is the name of the file.
03:11	This is the general syntax of 'sed' command.
03:15	Now, let us print the last line of the file.
03:20	Let me clear the prompt.
03:24	Now, type: sed space -n space within single quotes dollar-sign p after the single quotes space seddemo.txt
03:36	Press Enter.
03:39	We see that the last line is printed.
03:42	Now come back to text editor.
03:45	Suppose, we want to print the entries from 3rd to 6th.
03:50	For this, we need to type on the terminal:
03:54	sed space -n space within single quotes 3 comma 6p after the single quotes space seddemo.txt
04:07	Press Enter.
04:09	The output is displayed from the third line to the sixth line.
04:14	Any of the actions can be reversed by using the exclamation mark (!) before the action.
04:21	Say, if we had to print all lines except from 3rd to 6th, we will type:sed space -n space within single quotes 3 comma 6 (exclamation mark) !p
04:38	After the single quotes space seddemo.txt
04:45	Press Enter.The output is displayed.
04:49	Let us switch back to our slides.
04:52	Line addressing and context addressing.
04:56	So far, we specified the lines in the file on which the action needs to be taken.
05:02	This is known as line addressing;
05:05	address specified by the line numbers.
05:08	This is one way of addressing.
05:11	Another way of addressing is Context addressing.
05:16	Lines that contain particular context say a particular word.
05:21	If we want to take actions on lines that contain a particular word, we use context addressing.
05:29	Regular expressions can be used.
05:32	Let us see an example.
05:35	Come back to our text editor.
05:38	Say, we want to print those lines which have the word "computers".
05:44	Come back to our terminal.
05:46	Now, type:
05:48	sed space -n space within single-quotes front-slash opening square-bracket [cC] closing Square-bracket omputers/p after the single quotes space seddemo.txt
06:14	Press Enter.
06:16	We see the lines with the word "computers" is displayed.
06:22	We write pattern within square-brackets.
06:24	This is to match any one or both of the characters within square-brackets.
06:30	When we need to match patterns, the pattern needs to be typed between front slashes.
06:37	We can print it in a file as well using the w option. For this, type:
06:44	sed space -n space within single-quotes front-slash opening square-bracket [cC] closing square-bracket omputers/w space computer_student.txt after the single quotes space seddemo.txt
07:11	Press Enter.
07:14	Now, all the matching lines would be transferred to the file computer_student.txt.
07:21	Let us view the contents.
07:25	Type: cat space computer_student.txt
07:32	Press Enter.
07:35	We see the entries.
07:37	We can also have patterns that we can write to different files.
07:42	Let us clear the prompt.
07:45	Type: sed space -n space -e space (within single quotes) (front slash) ‘/electronics/w space electro.txt’ after the single quotes space -e space (within single quotes) (front slash) ‘/civil/w space civil.txt’ after the single quote space seddemo.txt
08:18	Press Enter.
08:22	Here, -e is used to combine multiple methods.
08:27	This would create two files- electro.txt and civil.txt.
08:34	To see what they contain, type:
08:37	cat space electro.txt
08:42	This will display the entries with the word "electronics".
08:47	Let us see the content of "civil" file.
08:50	Type: cat space civil.txt
08:55	press Enter.
08:57	This will display the entries having the word "civil".
09:01	We will see some more set of commands in another tutorial.
09:05	I will use the same program.
09:08	This brings us to the end of this tutorial.
09:11	Let us switch back to our slide.
09:14	we will summarize.In this tutorial, we learnt: sed
09:18	To print using sed.Line Addressing.
09:21	Context Addressing.
09:23	As an assignment,
09:25	use the same text file "seddemo.txt".
09:28	Try to print records from 6th to 12th line.
09:33	Watch the video available at the link shown below.
09:36	It summarizes the Spoken Tutorial project.
09:39	If you do not have good bandwidth, you can download and watch it.
09:44	The Spoken Tutorial project team:
09:46	Conducts workshops using spoken tutorials.
09:49	Gives certificates to those who pass an online test.
09:53	For more details, please write to contact@spoken-tutorial.org
10:00	Spoken Tutorial project is a part of the Talk to a Teacher project.
10:04	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:11	More information on this mission is available at: http://spoken-tutorial.org\NMEICT-Intro
10:17	This is Ashwini Patil from IIT Bombay, signing off. Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14