Linux/C3/The-sed-command/English

Sachin p:

review doneTitle of script: sed - The stream editor

Author: Sachin Patil and Anirban

Keywords: stream, editor, display, substitute, insert, delete

Visual Cue	Narration
Display slide 1	Welcome to this spoken tutorial on the sed - the stream editor.
Display slide 2 Learning objectives	In this tutorial we tutorial we will learn usage of sed command.
Display slide 3 System Requirement	To record this tutorial, I am using Ubuntu Linux 12.04 Operating System and GNU BASH version 4.2.24 Please note, GNU bash version 4 or above is recommended to practice this tutorial.
Display slide 4 Prerequisites	As prerequisites You should know Basics of linux terminal For relevant tutorials please visit our website: http://spoken-tutorial.org
Display slide 5 Introduction Let us start with an introduction to sed.	sed is one of the most versatile tool in Linux. Its a stream editor. sed finds some pattern of text in a particular location of a file. Then it behave as a display or editing function. It performs editing like insertion, substitution, deletion of the matched text.
Open the file seddemo.txt [enter]	Let us first start with some examples. We will see how to print using the sed command. I have a file called seddemo.txt in home directory. Let us view its content. In this file we have some enteries like roll no, name, stream, marks, pass or fail and the stipend amount.
At the prompt sed '2p' seddemo.txt [enter] Hover your mouse on the second line	Now suppose we want to print the second line of the file. For this we need to oepn the terminal by pressing CTRL + ALT and T keys simultaneously on your keyboard. Now Type: sed space (in single quotes) ‘2p’ space seddemo.txt Press Enter
	Here 2 denotes the location which is the second line. p denotes the action, which is printing(p). Look at the output. It shows the entire file but see that the second line is printed twice. This is the default behaviour of the action p.
At the prompt sed -n '2p' seddemo.txt [enter]	To only print the second line type: sed space (minus) -n space (in single quotes) 2p space seddemo.txt Press Enter.
Highlight -n 2 p seddemo.txt We see only the second line is printed.	-n stands for ‘silent mode’ which will suppress all unnecessary output. Then we give the location in the stream that we want to edit or display. We want to select the second line. p indicates the action we want to take ie to print the second line. And seddemo.txt is the name of the file This is the general syntax of sed command.
At the prompt sed -n '$p' seddemo.txt [enter]	Now let us print the last line type: sed space (minus) -n space (in single quotes) (dollar) $p space seddemo.txt Press Enter. We see that the last line is printed. Now come back to the text editor.
At the prompt sed -n '3,6p' seddemo.txt [enter]	Suppose we want to print the enteries from 3rd to 6th For this we need to type on the terminal: sed space (minus) -n space (in single quotes) ‘3 (comma) ,6p’ space seddemo.txt Press Enter. The output is displayed from the third line to the sixth line.
At the prompt sed -n '3,6!p' seddemo.txt [enter]	Any of the actions can be reversed by using the exclamation mark before the action. Say if we had to print all lines except from 3rd to 6th we would type: sed space (minus) -n space (in single quotes) ‘3 (comma) ,6 (exclamation mark) !p space seddemo.txt Press Enter. The output is displayed. Let us switch back to the slides. Line addressing and context addressing.
Display slide 6	So far, we specified the lines in the file on which the action needs to be taken. This is known as line addressing. Address specified by the line numbers. This is one way of addressing. Another way of addressing is Context addressing Lines that contain particular context say a particular word. If we want to take actions on lines that contain a particular word we use context addressing. Regular expressions can be used. Let us see an example. Come back to our editor.
At the prompt sed -n '/[cC]omputers/p' seddemo.txt [enter]	Say we want to print those lines which have the word computers. Come back to our temrinal. type: sed space (minus) -n space (in single quotes) (front slash)(opening square bracket) (opening square bracket) (front slash) ‘/[cC]omputers/p space seddemo.txt Press Enter. We see the lines with the word computers is displayed. We write pattern within square brackets. This is to match any one or both of the characters within square brackets. When we need to match patterns the pattern needs to be typed between front slashes.
At the prompt sed -n '/[cC]omputers/w computer_student' seddemo.txt [enter]	We can print it in file as well using the w option. For this type: sed space (minus) -n space (in single quotes) (front slash) (opening square bracket) (opening square bracket) (front slash) /[cC]omputers/w space computer_student space seddemo.txt Press Enter. Now all the matching lines would be transferred to the file computer_student.txt.
At the prompt cat computer_student [enter]	Let us view the content of computer_student type: cat space computer_student Press Enter.
At the prompt sed -n -e '/electronics/w electro’ -e ‘/civil/w civil' seddemo.txt” [enter]	We can also have patterns that we can write to different files. Type: sed space (minus) -n space (minus) -e space (in single quotes) (front slash) ‘/electronics/w space electro.txt’ (minus) -e space (in single quotes) (front slash) ‘/civil/w space civil.txt’ space seddemo.txt Press Enter -e is used to combine multiple methods Press Enter This would create two files electro.txt and civil.txt.
cat electro [enter] cat civil [enter]	To see what they contain type: cat space electro.txt This will display the enteries with the word electronics. Let us see the content of civil file. Then type: cat space civil.txt press Enter This will display the enteries having the word civil.
	We will see some more set of commands in another tutorial. I will use the same program.
Display slide 7 Summary	Let us summarize, In this tutorial we learnt, sed. To print using sed. Line Addressing. Context Addressing.
Assignment	As an assignment, Use the same text file seddemo.txt. Try to print records from 6th to 12th line.
Display Slide 8 Acknowledgement Slide	Watch the video available at the link shown below It summarises the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Display Slide 9 Spoken Tutorial Workshops	The Spoken Tutorial Project Team Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact@spoken-tutorial.org
Display Slide 10 Acknowledgement	Spoken Tutorial Project is a part of the Talk to a Teacher project 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
No Last Slide for tutorials created at IITB Display the previous slide only and narrate this line.

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