Difference between revisions of "Linux/C3/More-on-sed-command/English"

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'''Title of script''': sed - The stream editor
+
'''Title of script''': More on sed
  
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'''Author: Sachin Patil'''
+
'''Author: Sachin Patil and Anirban'''
  
 
'''Keywords: sed, substitute, insert, delete'''
 
'''Keywords: sed, substitute, insert, delete'''
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| style="border:1pt solid #000000;padding:0.106cm;"| Welcome to this spoken tutorial on some more on sed.
+
| style="border:1pt solid #000000;padding:0.106cm;"| Welcome to the spoken tutorial on more on sed.
  
 
|-
 
|-
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Learning objectives
 
Learning objectives
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| style="border:1pt solid #000000;padding:0.106cm;"| In this tutorial we tutorial we will learn some more '''sed '''commands.
+
| style="border:1pt solid #000000;padding:0.106cm;"| In this tutorial we tutorial we will learn some more on '''sed '''commands.
 +
 
 +
Through some examples.
  
 
|-
 
|-
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'''Ubuntu Linux''' 12.04''' Operating System''' and
 
'''Ubuntu Linux''' 12.04''' Operating System''' and
  
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'''GNU BASH''' version 4.2.24(1)
+
'''GNU BASH''' version 4.2.24
  
 
Please note,''' GNU bash''' version 4 or above is recommended to practice this tutorial.
 
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;"| The major use of sed is substitution.
 
| style="border:1pt solid #000000;padding:0.106cm;"| The major use of sed is substitution.
  
−
ie replacing some pattern in the input with something else.
+
Replacing some pattern in the input with something else.
  
 
|-
 
|-
 
| style="border:1pt solid #000000;padding:0.106cm;"| Type
 
| style="border:1pt solid #000000;padding:0.106cm;"| Type
  
−
'''cat seddemo.tx'''t
+
'''cat seddemo.txt'''
  
  
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<nowiki>[ </nowiki>Point to the fourth and sixth line ]
 
<nowiki>[ </nowiki>Point to the fourth and sixth line ]
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| style="border:1pt solid #000000;padding:0.106cm;"| Lets first look at the original file '''seddemo.txt'''
+
| style="border:1pt solid #000000;padding:0.106cm;"| Let's first look at the original file '''seddemo.txt'''
  
  
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If you want to replace all occurrences of the '''‘kumar’''' with '''‘Roy’'''
 
If you want to replace all occurrences of the '''‘kumar’''' with '''‘Roy’'''
  
−
Type
+
Type on the terminal
  
−
'''sed''' space ''''s<nowiki>/[</nowiki>kK]umar/Roy/'''' space '''seddemo.txt'''
+
'''sed''' space within single quote ''''s<nowiki>front slash / opening square bracket [</nowiki>k capital K closing square bracket ]umar slash/ Roy slash/'''' after the quotes space '''seddemo.txt'''
  
 
'''Press Enter'''
 
'''Press Enter'''
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|-
 
|-
 
| style="border:1pt solid #000000;padding:0.106cm;"| Show the output
 
| style="border:1pt solid #000000;padding:0.106cm;"| Show the output
−
 
−
 
−
Show the file
 
−
 
−
 
−
'''cat seddemo.txt'''
 
  
  
Line 117: Line 113:
 
This is because, by default, the first matched entry of any line is substituted.
 
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'''
+
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
 
| style="border:1pt solid #000000;padding:0.106cm;"| Type
  
−
'''sed''' space ''''s<nowiki>/[</nowiki>kK]umar/Roy/g'''' space '''seddemo.txt'''
+
'''sed''' space within single quotes ''''s<nowiki>/[</nowiki>kK]umar/Roy/g'''' after the single quote space '''seddemo.txt'''
  
−
And p'''ress Enter'''
+
And '''press Enter'''
  
 
Now, both entries of the fourth line are replaced.
 
Now, both entries of the fourth line are replaced.
Line 147: Line 143:
  
  
−
'''sed -e 's/electronics/electrical/g’ '''
+
'''sed -e 's/electronics/electrical/g’ '''
  
−
'''-e ‘s/civil/metallurgy/g' seddemo.txt'''
+
'''-e ‘s/civil/metallurgy/g' after the single quote space seddemo.txt'''
  
  
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| style="border:1pt solid #000000;padding:0.106cm;"| Type:
 
| style="border:1pt solid #000000;padding:0.106cm;"| Type:
  
−
'''sed''' space '''-e ‘s/electronics/electrical/g’ -e''' '''‘s/civil/metallurgy/g’''' space '''seddemo.txt'''
+
'''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.'''
 
And '''press Enter.'''
 +
 +
You can see that the words are replaced.
  
 
|-
 
|-
Line 175: Line 173:
 
In such case we would need to type:
 
In such case we would need to type:
  
−
'''sed''' space ''''/Anirban/s/computers/mathematics/g' '''space '''seddemo.txt'''
+
'''sed''' space within single quotes ''''/Anirban/s/computers/mathematics/g' ''' after the single quotes space '''seddemo.txt'''
  
 
Press '''Enter.'''
 
Press '''Enter.'''
 +
 +
We see that the stream is changed
 +
  
 
|-
 
|-
Line 208: Line 209:
 
|-
 
|-
 
| style="border:1pt solid #000000;padding:0.106cm;"|  
 
| 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.
+
| 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.'''
 
Say we want to select those lines which do not have stream as '''electronics.'''
Line 226: Line 227:
  
  
−
We would type:
+
type:
  
−
'''sed''' space (in single quotes) (front slash) /electronics/d space '''seddemo.txt''' space greater than sign space '''nonelectronics.txt'''
+
'''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'''
 
'''Press Enter'''
 +
 +
  
 
|-
 
|-
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| style="border:1pt solid #000000;padding:0.106cm;"| Say at the start of the file we want to add a line Student Information.
 
| 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.
+
For that we have the '''i''' action.
  
 
We need to type:
 
We need to type:
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And '''press''' '''Enter.'''
 
And '''press''' '''Enter.'''
 +
 +
You can see the output.
  
 
|-
 
|-
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Along with student information we also want to add academics in the next year.
 
Along with student information we also want to add academics in the next year.
 +
  
 
|-
 
|-
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sed space in single quotes 1i space Student Information'''\n'''2011' seddemo.txt  
+
sed space within single quotes 1i space Student Information'''\n'''2013' after the quotes space seddemo.txt  
  
 
'''Press Enter'''
 
'''Press Enter'''
  
−
Notice '''\n '''between the string ‘Information’ and ‘2011’.
+
Notice '''\n '''between the string ‘Information’ and ‘2013’.
  
−
'''\n '''prints 2011 in the next line after ‘Student Information’
+
'''\n '''prints 2013 in the next line after ‘Student Information’
  
 
|-
 
|-

Revision as of 15:31, 14 December 2013

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 tutorial we will learn some more on sed commands.

Through some examples.

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.

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 and once in the sixth line.


If you want to replace all occurrences of the ‘kumar’ with ‘Roy’

Type on the terminal

sed space within single quote 'sfront slash / opening square bracket [k capital K closing square bracket ]umar slash/ Roy 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]

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.

Infact 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.


Type


sed '1i Student Information\n2011' seddemo.txt


[enter]

So in that case we would write


sed space within single quotes 1i space Student Information\n2013' 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.

Contributors and Content Editors

Ashwini, Nancyvarkey

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