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

Learning objectives

System Requirement

Ubuntu Linux 12.04 Operating System and

GNU BASH version 4.2.24(1)

Please note, GNU bash version 4 or above is recommended to practice this tutorial.

Prerequisites

You should know Basics of linux terminal.

You should be aware of sed tool.

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http://spoken-tutorial.org

ie replacing some pattern in the input with something else.

cat seddemo.txt

[enter]

[ Point to the fourth and sixth line ]

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

[enter]

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

Type

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

Press Enter

Show the file

cat seddemo.txt

[point to 4th line of both output and file]

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

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

[enter]

sed space 's/[kK]umar/Roy/g' 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.

And civil with metallurgy in the file seddemo.txt

sed -e 's/electronics/electrical/g’

-e ‘s/civil/metallurgy/g' seddemo.txt

[enter]

sed space -e ‘s/electronics/electrical/g’ -e ‘s/civil/metallurgy/g’ space seddemo.txt

And press Enter.

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

[enter]

In such case we would need to type:

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

Press Enter.

[highlight ‘Anirban’]

[highlight ‘s’]

[highlight ‘computers’]

[highlight ‘mathematics’]

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.

Say we want to select those lines which do not have stream as electronics.

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

[enter]

We would type:

sed space (in single quotes) (front slash) /electronics/d space seddemo.txt space greater than sign space nonelectronics.txt

Press Enter

[enter]

cat space nonelectronics.txt

and press enter.

sed '1i Student Information' seddemo.txt

[enter]

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.

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.

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

[enter]

sed space in single quotes 1i space Student Information\n2011' seddemo.txt

Press Enter

Notice \n between the string ‘Information’ and ‘2011’.

\n prints 2011 in the next line after ‘Student Information’

In this tutorial we learnt,

Substitution

Replacement

Insertion

Take the same text file seddemo.txt

And try to replace or substitute name Ankit with Ashish

Acknowledgement Slide

It summarises the Spoken Tutorial project

If you do not have good bandwidth, you can download and watch it

Spoken Tutorial Workshops

Conducts workshops using spoken tutorials

Gives certificates to those who pass an online test

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Acknowledgement

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

Display the previous slide only and narrate this line.

This is Ashwini PAtil from IIT bombay sighning off.

Thank you for joining.