Search a line and replace line

Question

false###File.txt 
many rows
###online = false --> ONE SHOT import (delete all table contents before importing)
###online = true  --> DIFFERENTIAL import (import without clean the table contents)
###online = true

many rows

I want to select lines having online alone and replace true with false but it need not be row number 3 it can come anywhere in the file

My attempt : test.sh

online=true
perl -i -p -e "s/^(online[ ]*=[ ]*).*$/\1 $online/" File.txt 

It does the work but adds a space before false. Can someone correct above command so that it doesnt add a space before the word true

Answer 1

You can try sed:

sed -i '3s/true/false/' file.txt

If you want to keep the original file as file.txt.bak:

sed -i.bak '3s/true/false/' file.txt

Also if you want to replace more than one occurrence of true with false in the same line:

sed -i.bak '3s/true/false/g' file.txt

EDIT: As per your clarified query, Try this:

sed -i.bak '/DIFFERENTIAL\|[^t][^r][^u][^e]$/!s/true/false/' file.txt

This will replace "true" with "false" in the lines where there is no "DIFFERENTIAL" and also where "true" comes at the end of the line.

Answer 2

I found following command that will help me:

sed '/DIFFERENTIAL/!s/true/false/g'