How to exclude several lines around match with grep or similar tool?

Question

I can find all non-matched lines of file with grep -v 'my_pattern' some_file. Also i can print few strings before/after/around match with -A, -B or -C options of grep. But i can't combine these two options to exclude lines with pattern and certain amount of lines near matched lines - grep shows entire file as result. For example, i have log with a lot of patterns like this:

25.02.2012 10:41:37 here goes memory state
25MiB free
16MiB allocated
max free block is 4MiB

I'd like to filter them. Of course, i can write custom perl/awk script, but is there more elegant way to do this?

The awk solution can be found here: http://stackoverflow.com/a/9443740/851677. — jfg956, Feb 25 '12 at 11:58
Use sed http://stackoverflow.com/questions/4396974/sed-delete-n-lines-following-a-pattern — Eric Woodruff, Sep 24 '14 at 17:05

score 1 · Answer 1 · answered Oct 22 '20 at 17:44

A grep solution:

grep -C2 pattern file | grep -vFf- file

This uses grep -C2 to get the lines from file that you wish to exclude.

Then grep -vFf- takes those lines from stdin and will report all lines not matching.

Caution: This will eliminate all lines matching the 'context' elsewhere in file. So if the context contains a blank line, you will remove all blank lines.

kev · Accepted Answer · 2012-02-25T08:02:14.107

1

You can use the vim text editor:

:g/my_pattern/-2,//+2d

edited Feb 25 '12 at 08:02

answered Feb 25 '12 at 07:52

kev

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one thing i can't undestand - what's the difference between `:g/my_pattern/-2,//+2d` and `:g/my_pattern/-2,+2d`? It looks like they both do the same thing. – Andrey Starodubtsev Feb 25 '12 at 08:33
I don't know what the difference is, but I tried both out on a large file. ``:g/my_pattern/-2,+2d`` worked as expected, but ``:g/my_pattern/-2,//+2d`` removed more lines than expected. – DavidW Aug 26 '21 at 12:26

How to exclude several lines around match with grep or similar tool?

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