sed seach and replace word script

asteroid4u · 12-08-2016, 04:11 AM

Hi,

I need to search keyword and replace the next key word (that is after = ). Below is the file output

file1
bob=123
cape=abc
bod=xyz

search cape and replcae its value

I am trying below script but it is changing to all the lines. I execute script like sh

sh test.sh cape

a=Grear
b=$1
sed -i "/.*/${b}=${a}" /root/file

I am expecting file out put looks like below

file1
bob=123
cape=Gear
bod=xyz

Please help

Turbocapitalist · 12-08-2016, 04:18 AM

It will help to wrap the code in [code] [/code] tags so it is more readable.

But as to the content of your question, you'll need to use s in sed. It is usually used like this:

Code:

sed -e "s/old/new/"

There are a lot of tutorials on sed around. Here is a good one to get an overview from:

http://www.grymoire.com/Unix/Sed.html

Then you can broaden or narrow your search.

asteroid4u · 12-08-2016, 04:27 AM

Hi Turbocapitalist,

I won't get old value to search and replace.

I have key word exit in file say cape=xyz and I want to replace xyz with new value that produced by script.

Turbocapitalist · 12-08-2016, 04:37 AM

Quote:

Originally Posted by asteroid4u

Hi Turbocapitalist,

I won't get old value to search and replace.

I have key word exit in file say cape=xyz and I want to replace xyz with new value that produced by script.

Then you'll still need the s command in sed and when you have the following

Code:

sed -e "s/old/new/"

you can use a pattern for "old". See man 7 regex for the hairy details.

Don't try to use the -i option until you have a working pattern.

So you might try something like this:

Code:

#!/bin/sh
a=Grear
b=$1
sed -e "s/^${b}=.*$/${b}=${a}/" /root/file

But there are several other ways to do it as well.

asteroid4u · 12-08-2016, 04:45 AM

Thanks a lot it worked

Turbocapitalist · 12-08-2016, 04:52 AM

Great. Be sure to take a look at the link in #2 above and then skim through the regex manual page. It is more important that you understand why it worked than whether it worked or not.

The $a and $b are environment variables and being wrapped in double quotes means that the shell will interpret them early on. Then ^ stands for the start of the line itself and $ stands for the end of the line itself.

MadeInGermany · 12-08-2016, 01:55 PM

Or with a back-reference: \1 puts back what matched within the 

Code:

sed "s/^\(${b}=\).*/\1${a}/" /root/file