match a pattern and delete 3 lines before pattern along with the matched pattern line

Question

Trying to delete 4 lines in a file. First want to delete the Pattern matched line, along with it also need to delete 3 lines before the pattern match.

Eg:
1.land service=bus
2.land service=car
3.land service=truck
4.land service=cycle
5.
6.air service=plane
7.air service=rocket

My pattern match is in line 6. (i.e: air service=plane) based on that i need to delete line's 6,5,4,and 3.

My output looks like.
1.land service=bus
2.land service=car
3.air service=rocket

Tried the below code: grep -B2 'air service=plane' pattern.txt | sed -n '1,3p'

i am trying to use sed and awk to delete these lines in a file, could you please advise the best method to do so.

Possible duplicate of [Printing with sed or awk a line following a matching pattern](https://stackoverflow.com/questions/17908555/printing-with-sed-or-awk-a-line-following-a-matching-pattern) — kvantour, May 08 '19 at 15:12
Have a look at this excellent exhaustive answer: https://stackoverflow.com/a/17914105/8344060 — kvantour, May 08 '19 at 15:12

oguz ismail · Accepted Answer · 2019-05-08T12:09:00.797

2

One option is using tac and sed like this:

tac file | sed '/air service=plane/,+3d' | tac

To save changes, use a temporary file:

tac file | sed '/air service=plane/,+3d' | tac > tmpfile && mv tmpfile file

edited May 08 '19 at 12:09

answered May 08 '19 at 11:03

oguz ismail

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score 0 · Answer 2 · answered May 08 '19 at 11:42

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try this:

tac yourfile.txt | sed "/air service=plane/{N;N;N;d}" | tac

explanation:

tac yourfile.txt               # reverse file

sed "/air service=plane/       # find pattern
{N;N;N;d}"                     # concatenate next 3 lines (N) and delete (d)

tac                            # reverse output

output

1.land service=bus
2.land service=car
7.air service=rocket

answered May 08 '19 at 11:42

UtLox

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Thanks for the info. how you modify the file. this doesnot modfies the file. – Full - Stack - Developer May 08 '19 at 11:51

match a pattern and delete 3 lines before pattern along with the matched pattern line

2 Answers2