How to delete a line matching a pattern and a line after it using sed?

Question

I have a file that looks something like this:

good text good text FLAG bad text bad text good text good text good test bad Text FLAG bad text bad text good text 

I need to delete any line containing "FLAG", and I always need to delete one line immediately after the line "FLAG".

"FLAG" lines are found quite irregularly, and I can not rely on any strategy with line numbers.

Does anyone know how to do this with sed?

Answer 1

Using the GNU extension sed version:

 sed -e '/FLAG/,+1 d' infile 

This gives:

 good text good text good text good text good test good text 

Answer 2

This works and does not depend on any extensions:

 sed '/FLAG/{N d }' infile 

N reads the next line in the pattern space, then d deletes the pattern space.

Answer 3

Here is one way: awk :

 awk '/FLAG/{f=1;next}f{f=0;next}1' file 

or

 awk '/FLAG/{getline;next}1' file