BOSS-Linux/C3/More-on-sed-command/English

Title of script: More on sed

Author: Sachin Patil and Anirban

Keywords: sed, substitute, insert, delete

Visual Cue	Narration
Display slide 1	Welcome to the spoken tutorial on More on sed.
Display slide 2 Learning objectives	In this tutorial, we will learn some more sed commands, through some examples.
Display slide 3 System Requirement	To record this tutorial, I am using Linux 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. You should be aware of sed tool. For relevant tutorials please visit our website: http://spoken-tutorial.org
	The major use of sed is substitution. Replacing some pattern in the input with something else.
Type cat seddemo.txt [enter] [ Point to the fourth and sixth line ]	Let's first look at the original file seddemo.txt
Type sed 's/[kK]umar/Roy/' seddemo.txt [enter]	Notice the word Kumar occurs two times in the fourth line and once in the sixth line. If you want to replace all occurrences of ‘Kumar’ with ‘Roy’, type on the terminal sed space within single quote 's front slash / opening square bracket [k capital K closing square bracket ]umar front slash/ Roy front slash/' after the quotes space seddemo.txt Press Enter.
Show the output [point to 4th line of both output and file]	Notice the fourth line. Only the first occurrence of Kumar is changed to Roy, not the second one. Sixth line had one occurrence of the word Kumar and this is replaced now.
	So, we see only the first entry of the lines has been changed. This is because, by default, the first matched entry of any line is substituted.
	To substitute all the matched entries we need to use the flag g option.
Type sed 's /[ kK]umar/Roy/g' seddemo.txt [enter]	Let me clear the prompt. Type sed space within single quotes 's /[ kK]umar/Roy/g' after the single quote space seddemo.txt And press Enter Now, both entries of the fourth line are replaced.
	We can make multiple substitutions in one go as well. Say we want to replace the words electronics with the word electrical And civil with metallurgy in the file seddemo.txt
Type sed -e 's/electronics/electrical/g’ -e ‘s/civil/metallurgy/g' after the single quote space seddemo.txt [enter]	Type: sed space -e space within single quotes ‘s/electronics/electrical/g’ -e ‘s/civil/metallurgy/g’ after the single quote space seddemo.txt And press Enter. You can see that the words are replaced.
Type sed '/Anirban/s/computers/mathematics/' seddemo.txt [enter]	Now we want to change the stream of Anirban from computers to mathematics. In such case we would need to type: sed space within single quotes '/Anirban/s/computers/mathematics/g' after the single quotes space seddemo.txt Press Enter. We see that the stream is changed.
[highlight text inside single quotes] [highlight ‘Anirban’] [highlight ‘s’] [highlight ‘computers’] [highlight ‘mathematics’]	Let us understand what this is. First we write sed then in single quotes we write the pattern to be matched. This is Anirban. Now after the slash comes the operation. This is s that stands for substitution, as we have already seen. Then we mention the pattern to be replaced which is computers. Then the new word that would be substituted, which is mathematics.
	We can also use sed to add or delete lines in the file. Say we want to select those lines which do not have stream as electronics.
Type sed '/electronics/d' seddemo.txt > nonelectronics.txt [enter]	For that, we have the d flag. type: sed space (within single quotes) (front slash) /electronics/d after the single quotes space seddemo.txt space greater than sign space nonelectronics.txt Press Enter.
cat nonelectronics.txt [enter]	To see the contents, type: cat space nonelectronics.txt and press Enter.
Type sed '1i Student Information' seddemo.txt. ] [enter]	Say, at the start of the file we want to add a line Student Information. For that we have the i action.
	We need to type: sed space in single quotes '1i space Student Information' seddemo.txt And press Enter. You can see the output.
	In fact, we can enter multiple lines like this. Say, we want to add the two lines we would do it in a similar way. Along with Student Information we also want to add academics in the next year.
So we can type sed '1i Student Information\n2013' seddemo.txt [enter]	So in that case we would write sed space within single quotes i space Student Information \n 2013' after the quotes space seddemo.txt Press Enter
	Notice \n between the string ‘Information’ and ‘2013’. \n prints 2013 in the next line after ‘Student Information’
	This brings me to the end of this tutorial.
Summary	Let us summarize, In this tutorial we learnt, Substitution Replacement Insertion
Assignment	As an assignment, Take the same text file seddemo.txt And try to replace or substitute name Ankit with Ashish
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.	The script has been contributed by Sachin Patil. This is Ashwini PAtil from IIT bombay sighning off. Thank you for joining.

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