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Sed Command in Unix with examples | Stream Editor in Unix

Sed Command in Unix :

In Previous articles i have explained about file commands in unix,directory commands,Filter commands in unix.In this article i will explain Sed Command in unix which will help to modify the files in unix.Sed command in unix is basically used to replace and find the text but sed command also used to do many things apart from replacing the text.It is used to search and replace a string and it is multi-purpose filter string.

Syntax:

Sed “s/old string/new string/g”

s: means substitution

g: means every line all occurrences

without g: means every line 1^st occurrences

Real Life Examples with options :

Create a file :

$cat>Sed_File

a b c complexsql d e complexsql f complexsql

complexsql a b complexsql

complexsql abc complexsql

complexsqlabccomplexsql

technologiesabc

technologyabc

techie

tech

333

4444

55555

Ctrl+d

Examples:

1) sed “s/complexsql/Amit/g” Sed_File:

The above command replaces the word complexsql to Amit.Here s stands for substitution and g stands for every line.

2) sed “s/complexsql/Amit/gi” Sed_File:

The above command adds the new line before word complexsql and replaces word complexsql to Amit.

3) sed “s/complexsql/Amit/” Sed_File:

The above command directly substitudes the word complexsql to Amit.

4) sed “s/complexsql/Amit/i” Sed_File

5) sed “s/^tech/Amit/g” Sed_File:

It replaces “tech” with Amit

6) sed “s/^tech$/Amit/g” Sed_File :

It replaces exactly “tech” with Amit by checking uppercase and lowercase letters.

7) sed “s/\<tech\>/Amit/g” Sed_File :

It replaces exactly “tech” with Amit.This is another syntax for replacing the words by checking case sensitivity.

8) sed “s/^$/***Blank Lines***/g” Sed_File:

It replaces all Empty Lines with “***Blank Lines***”

9) sed “s/\<complexsql\>//gi” Sed_File :

It deletes “complexsql” word from the file

10) sed “s/[0-9][0-9]/*/g” Sed_File:

It replace 2 digit number with “*”

11) sed “s/[0-9]/@/g” Sed_File:

It replaces “n” digits with “@”

12) sed “s/[0-9]{3,4}/@/g” Sed_File

13) sed -n “3p” Sed_File:

It Prints 3^rd line

14) sed -n “3,5p” Sed_File:

It Prints 3^rd to 5^th lines

15) sed -n “1p” Sed_File:

It Prints 1^st line from a file

15A) head -1 Sed_File:

It Prints 1^st line from a file

16) sed -n ‘$p’ sed_file:

It Prints Last Record from a file

16A) tail -1 Sed_File:

It Prints Last Record from a file

17) $sed -n ‘1,$p’ Sed_File:

It Prints 1^st to Last Record from a file

18) $ sed -n ‘1p :

It Prints 1^st& Last Record from a file

> $p’ Sed_File

19) $ sed -n ‘1p;$p’ Sed_File:

It Prints 1^st& Last Record from a file

20) $ sed ‘1d’ Sed_File:

It Deletes first line from a file

21) $ sed ‘4d’ Sed_File:

It Deletes 4th line from a file

22) $ sed ‘3,5d’ Sed_File :

It Deletes 3^rd to 5^th Lines from a file

23) $ sed ‘$d’ Sed_File:

It Deletes Last Line from a file

24) $ sed ‘3,5w Temp_File’ Sed_File:

It Writes/Copies 3^rd to 5^th line from Sed_File to Temp_File

Piping (|):

It is used to combine two or more commands

Note: Pipe always execute left side command & O/P goes to right side as I/P

1) Count number of users connected to the server?

$ who | wc –l

2) Count number of files in current directory?

$ ls | wc–l

3) Count total number of sub-directories in current directory?

$ ls -l | grep ‘^d’ | wc–l

4) Display today’s date day?

$ date | cut -c 1-3

tee:It is used to write data to the file as well as to the screen.

1) $ cat Amit| tee Temp

It copies Amitfile data to Temp and also displays data to the screen

2) $ cat Amit| tee Temp Temp1

It copies Saif file data to Temp, Temp1 and also displays data to the screen

Head:It displays FIRST ‘n’ lines from a file

$ head -1 Amit

It displays FIRST line from the file.

$ head -3 Amit

It displays FIRST 3 lines from the file.

Tail:It displays LAST ‘n’ lines from a file

$ tail -1 Amit

It displays LAST line from the file.

$ tail -3 Amit

It displays LAST 3 lines from the file.

Note: By Default, head & tail displays 10 lines of a given file.

Click on Topic You want to learn:

Unix Tutorials :

1.What is unix?

2.Basic unix commands

3.File Commands in unix

4.Create File in Unix using multiple ways

12.paste Command

Hope this article is useful for unix learners.If you like this article dont forget to comment in comment section.

Amit S

Oracle Consultant with vast experience in Oracle BI and PL/SQL Development. Amiet is the admin head of this website who contributes by preparing tutorials and articles related to database technologies. He is responsible to manage the content and front-end of the website.