Using sed command change a string on a certain line with a certain string

Question

I need to use sed to change a string in a file only on the 4th line if it contains a string called "test"

So basically What I got right now is:

sed '/test/ s/abc/zz/g' sample 

This will basically look through the lines and see if it has test and than change the abc to zz if its in that line.

But how do I do it only for the 4th line.

I tried

 sed '/test/ 4s/abc/zz/g' sample 

Adding the 4 infront of the s , but it doesnt work.

Answer 1

One way:

sed -e '4 { /test/s/abc/zz/g }' <file 

Answer 2

I am not sure, but would something like this work?

awk 'NR==4 {print $0}' filename.txt | grep 'test' | sed 's/abc/xyz/g' 

Answer 3

another way:

first find the line with that string "test":

LINE=$(grep "test" file -n | awk '{print $1}' | cut -d ':' -f1 | xargs)

then using that variable LINE do:

sed "s$LINEs/abc/zzz/g" file

Answer 4

you can use this

sed -i '4s/old_text/new_text/g' file_name