View source for BOSS-Linux/C3/More-on-sed-command/English

'''Title of script''': More on sed

'''Author: Sachin Patil and Anirban'''

'''Keywords: sed, substitute, insert, delete'''



{| style="border-spacing:0;"
| style="border:1pt solid #000000;padding:0.106cm;"| '''Visual Cue'''
| style="border:1pt solid #000000;padding:0.106cm;"| '''Narration'''

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| style="border:1pt solid #000000;padding:0.106cm;"| Display slide 1

| style="border:1pt solid #000000;padding:0.106cm;"| Welcome to the spoken tutorial on '''More on sed.'''

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| style="border:1pt solid #000000;padding:0.106cm;"| Display slide 2

Learning objectives
| style="border:1pt solid #000000;padding:0.106cm;"| In this tutorial, we will learn some more '''sed '''commands, through some examples.

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| style="border:1pt solid #000000;padding:0.106cm;"| Display slide 3

System Requirement



| style="border:1pt solid #000000;padding:0.106cm;"| 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.

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| style="border:1pt solid #000000;padding:0.106cm;"| Display slide 4

Prerequisites



| style="border:1pt solid #000000;padding:0.106cm;"| 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

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| The major use of '''sed''' is substitution.

Replacing some pattern in the input with something else.

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| style="border:1pt solid #000000;padding:0.106cm;"| Type

'''cat seddemo.txt'''


<nowiki>[</nowiki>enter]


<nowiki>[ </nowiki>Point to the fourth and sixth line ]
| style="border:1pt solid #000000;padding:0.106cm;"| Let's first look at the original file '''seddemo.txt'''


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| style="border:1pt solid #000000;padding:0.106cm;"| Type


'''sed 's<nowiki>/[</nowiki>kK]umar/Roy/' seddemo.txt'''


<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| 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'''.

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| style="border:1pt solid #000000;padding:0.106cm;"| Show the output


[point to 4th line of both output and file]
| style="border:1pt solid #000000;padding:0.106cm;"| 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.

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| 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.

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| To substitute all the matched entries we need to use the flag ''' g''' option.

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| style="border:1pt solid #000000;padding:0.106cm;"|Type


'''sed 's /[ kK]umar/Roy/g' seddemo.txt'''


<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| 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.

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"|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'''

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| style="border:1pt solid #000000;padding:0.106cm;"| Type


'''sed -e  's/electronics/electrical/g’ '''

'''-e ‘s/civil/metallurgy/g' after the single quote space seddemo.txt'''


<nowiki>[</nowiki>enter]



| style="border:1pt solid #000000;padding:0.106cm;"| 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.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Type


'''sed '/Anirban/s/computers/mathematics/' seddemo.txt'''


<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| 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.


|-
| style="border:1pt solid #000000;padding:0.106cm;"| <nowiki>[</nowiki>highlight text inside single quotes]


<nowiki>[</nowiki>highlight ‘Anirban’]


<nowiki>[</nowiki>highlight ‘s’]


<nowiki>[</nowiki>highlight ‘computers’]


<nowiki>[</nowiki>highlight ‘mathematics’]
| style="border:1pt solid #000000;padding:0.106cm;"| 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'''.

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| 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.'''

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| style="border:1pt solid #000000;padding:0.106cm;"| Type


'''sed '/electronics/d' seddemo.txt > nonelectronics.txt'''


<nowiki>[</nowiki>enter]



| style="border:1pt solid #000000;padding:0.106cm;"| 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'''.


|-
| style="border:1pt solid #000000;padding:0.106cm;"| '''cat nonelectronics.txt'''


<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| To see the contents, type:

'''cat space nonelectronics.txt'''

and press '''Enter.

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| style="border:1pt solid #000000;padding:0.106cm;"| Type


'''sed '1i Student Information' seddemo.txt'''. ]


<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| Say, at the start of the file we want to add a line '''Student Information'''.

For that we have the '''i''' action.

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| We need to type:

'''sed space''' in single quotes ''''1i space Student Information' seddemo.txt '''

And press '''Enter.'''

You can see the output.

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| 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.


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| style="border:1pt solid #000000;padding:0.106cm;"| So we can type


'''sed '1i Student Information\n2013' seddemo.txt'''


<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| 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'''

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| 
Notice '''\n '''between the string ‘Information’ and ‘2013’.

'''\n '''prints 2013 in the next line after ‘Student Information’

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| style="border:1pt solid #000000;padding:0.106cm;"| 
| style="border:1pt solid #000000;padding:0.106cm;"| This brings me to the end of this tutorial.

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| style="border:1pt solid #000000;padding:0.106cm;"| Summary
| style="border:1pt solid #000000;padding:0.106cm;"| Let us summarize,

In this tutorial we learnt,

Substitution 

Replacement

Insertion

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| style="border:1pt solid #000000;padding:0.106cm;"| Assignment
| style="border:1pt solid #000000;padding:0.106cm;"| As an assignment,

Take the same text file '''seddemo.txt'''

And try to replace or substitute name '''Ankit''' with '''Ashish'''

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| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 8

Acknowledgement Slide



| style="border:1pt solid #000000;padding:0.106cm;"| 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

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 9

Spoken Tutorial Workshops



| style="border:1pt solid #000000;padding:0.106cm;"| 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

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| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 10

Acknowledgement



| style="border:1pt solid #000000;padding:0.106cm;"| 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

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| style="border:1pt solid #000000;padding:0.106cm;"| No Last Slide for tutorials created at IITB 

Display the previous slide only and narrate this line.
| style="border:1pt solid #000000;padding:0.106cm;"| The script has been contributed by Sachin Patil.

This is Ashwini PAtil from IIT bombay sighning off.

Thank you for joining.

|}