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

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Revision as of 12:52, 12 February 2015

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 as shown: http://spoken-tutorial.org
00:44 Let us 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 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.
01:18 I have a file called seddemo.txt in home directory version.
01:23 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.
01:38 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
01:48 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(p).
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 behaviour of the 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 as 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 ie 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 promt
03:24 Now Type
03:25 sed space -n space within single quotes (dollar) $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 enteries 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’ 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.
04:46 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 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 quotesspace 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 file as well using the w option.
06:43 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 content
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 promt
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 enteries 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 enteries 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,
09:15 In this tutorial we learnt,sed
09:18 To print using sed.
09:19 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 summarises 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