Difference between revisions of "Linux/C3/The-sed-command/English-timed"

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Revision as of 15:49, 21 July 2014

Time Narration
00:01 Welcome to this spoken tutorial on the sed - the stream editor.
00:05 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 usingUbuntu 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 as shown: http://spoken-tutorial.org
00:45 Let us 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 first 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 content.
01:26 In this file we have some enteries 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 oepn 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 behaviour 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 ie 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 promt
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.
03:43 We see that the last line is printed.
03:49 Now come back to text editor.
03:51 Suppose we want to print the enteries 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 editor.
05:44 Say we want to print those lines which have the word computers.
05:50 Come back to our temrinal.
05:53 Now Type
05:54 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 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)Computers/w space computer_student.txt after the 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
07:43 We can also have patterns that we can write to different files.
07:50 Let us clear the promt
07:52 Type sed space -n space -e space (within single quotes) (front slash) ‘/electronics/w space electro.txt’ after the single quotes -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 enteries with the word electronics.


08:54 Let us see the content of civil file.
08:58 Type cat space civil.txt
09:01 press Enter
09:03 This will display the enteries 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.
09:26 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 summarises 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 from IIT Bombay signing off . Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14