sed command for searching multiple strings and replace one of the string

Question

I would need to edit a param value, in a specific block. Can you help with the sed command in this. I know to do this with a perl script, but i need in one single command

My file looks like this

Block 1
   Param1=val1
   Param2=val2
   .
   .

Block 2
   Param1=val1
   Param2=val2
   .
   .

Block 3
.
.
.

What is your expect output ?

Kalanidhi
– Kalanidhi

2015-11-06 09:39:42 +00:00
Commented Nov 6, 2015 at 9:39 — Kalanidhi
– Kalanidhi, Commented Nov 6, 2015 at 9:39
Replace parameter value like Param1=modifiedval1

cms
– cms

2015-11-06 09:48:52 +00:00
Commented Nov 6, 2015 at 9:48 — cms
– cms, Commented Nov 6, 2015 at 9:48

Kent · Accepted Answer · 2015-11-06 09:52:31Z

1

You can make use of sed's address: /pattern1/,/pattern2/ to handle only one "block". For example, if you just want to change Param1 in Block 1:

sed -r '/^Block 1/,/^Block 2/s/(\s*Param1=).*/\1NEW/' file

If you have many blocks, you can use ^Block 1$ or ^Block 1\s*$. This won't get mess with for example: Block 120

answered Nov 6, 2015 at 9:52

Kent

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2 Comments

cms Over a year ago

Kent, I need to modify the parameter value in one of the blocks only. I tried this sed -r '/^Block 1/s/(\sParam1=.)/\1Param1=newvalue/' file. It did not edit. Am I missing anything

Kent Over a year ago

@cms my cmd will output the result (with param1 changed). If you want to change the file, add -i option to your gnu sed.

potong · Accepted Answer · 2015-11-06 11:55:14Z

0

This might work for you (GNU sed):

sed -ri '/^Block/h;G;s/(Param1=)\S+(.*\nBlock 2)$/\1newval\2/;P;d' file

Store the current block in the hold space and append the block variable to each line of the file. Substitute a new parameter value if there is a match on the parameter and the block variable. Print every line and delete the block variable.

N.B. the solution above replaces parameter 1 in block 2, tailor the solution for your needs.

edited Nov 6, 2015 at 11:55

answered Nov 6, 2015 at 11:48

potong

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