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

Time	Narration
00:01	Welcome to this spoken tutorial on sed - the stream editor.
00:05	In this tutorial, we will learn usage of sed command.
00:11	We will do this through some examples.
00:14	To record this tutorial,
00:16	I am using Ubuntu Linux version 12.04 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.
00:34	As prerequisites,
00:36	you should know basics of Linux terminal.
00:39	For relevant tutorials please visit our website which is as shown: http://spoken-tutorial.org
00:45	Let us start with an introduction to sed:
00:48	sed is a stream editor.
00:51	sed finds some pattern of text in a particular location of a file.
00:58	It performs some display or editing function-
01:02	editing function 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.
01:19	I have a file called seddemo.txt in home directory version.
01:24	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.
01:39	Now, suppose we want to print the second line of the file.
01:44	For this, we need to open the terminal by pressing Ctrl + Alt and T keys simultaneously on your keyboard.
01:53	Now type:
01:55	sed space within single quotes ‘2p’ after the single quotes space seddemo.txt
02:03	Press Enter.
02:06	Here, 2 denotes the location which is the second line.
02:11	p denotes the action, which is printing(p).
02:16	Now Look at the output.
02:18	It shows the entire file but see that the second line is printed twice.
02:25	This is the default behavior of the action p.
02:29	To only print the second line,
02:31	type:
02:33	sed space -n space (Within single quotes) 2p after the single quotes space seddemo.txt
02:44	Press Enter.
02:46	We see only the second line as printed.
02:51	-n stands for ‘silent mode’ which will suppress all unnecessary output.
02:58	Then we give the location in the stream that we want to edit or display.
03:03	We want to select the second line.
03:07	p indicates the action we want to take i.e to print the second line.
03:12	And seddemo.txt is the name of the file.
03:18	This is the general syntax of sed command.
03:21	Now let us print the last line of the file.
03:26	Let me clear the prompt.
03:29	Now type:
03:32	sed space -n space within single quotes (dollar) $p after the single quotes space seddemo.txt
03:42	Press Enter.We see that the last line is printed.
03:49	Now come back to our text editor.
03:51	Suppose we want to print the entries from 3rd to 6th.
03:57	For this, we need to type on the terminal:
04:00	sed space -n space within single quotes 3 (comma) ,6p’ space seddemo.txt
04:14	Press Enter.
04:16	The output is displayed from the third line to the sixth line.
04:21	Any of the actions can be reversed by using the exclamation mark before the action.
04:28	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
04:44	after the single quotes space seddemo.txt
04:51	Press Enter.
04:53	The output is displayed.
04:56	Let us switch back to our slides.
04:58	Line addressing and context addressing.
05:03	So far, we specified the lines in the file on which the action needs to be taken.
05:09	This is known as line addressing-
05:12	address specified by the line numbers.
05:15	This is one way of addressing.
05:18	Another way of addressing is Context addressing-
05:22	lines that contain particular context say a particular word.
05:28	If we want to take actions on lines that contain a particular word, we use context addressing.
05:36	Regular expressions can be used.
05:39	Let us see an example.
05:42	Come back to our text editor.
05:44	Say, we want to print those lines which have the word computers.
05:50	Come back to our terminal.
05:53	Now type:sed space -n space within single quotes front slash (opening square bracket) [cC] (Closing Square bracket) omputers/p after the single quotesspace seddemo.txt
06:20	Press Enter.
06:23	We see the lines with the word "computers" is displayed.
06:28	We write pattern within square brackets.
06:31	This is to match any one or both of the characters within square brackets.
06:36	When we need to match patterns, the pattern needs to be typed between front slashes.
06:43	We can print it in a file as well, using the w option.
06:50	For this type:
06:52	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
07:18	Press Enter.
07:21	Now all the matching lines would be transferred to the file computer_student.txt.
07:27	Let us view the content of computer_student
07:31	Type: cat space computer_student.txt
07:38	Press Enter.
07:42	We see the entries.We can also have patterns that we can write to different files.
07:50	Let us clear the prompt.
07:52	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
08:24	Press Enter
08:28	Here -e is used to combine multiple methods.
08:34	This would create two files electro.txt and civil.txt.
08:41	To see what they contain, type:
08:43	cat space electro.txt
08:49	This will display the entries with the word "electronics".
08:54	Let us see the contents of civil file.
08:58	Type: cat space civil.txt
09:01	press Enter.
09:03	This will display the entries having the word "civil".
09:08	We will see some more set of commands in another tutorial.
09:12	I will use the same program.
09:14	This brings us to the end of this tutorial.
09:18	Let us switch back to our slide.
09:20	we will summarize,
09:22	In this tutorial we learnt, sed:
09:25	To print using sed.Line Addressing.
09:27	Context Addressing.
09:30	As an assignment,
09:32	use the same text file seddemo.txt,
09:35	try to print records from 6th to 12th line.
09:40	Watch the video available at the link shown below.
09:42	It summarizes the Spoken Tutorial project.
09:46	If you do not have good bandwidth, you can download and watch it.
09:51	The Spoken Tutorial Project Team:
09:53	Conducts workshops using spoken tutorials
09:55	Gives certificates to those who pass an online test.
10:00	For more details, please write tocontact@spoken-tutorial.org.
10:07	Spoken Tutorial Project is a part of the Talk to a Teacher project.
10:11	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:18	More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro.
10:25	This is Ashwini Patil from IIT Bombay, signing off . Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14