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Inverting match with grep, unless another term exists (lemmy.world)
submitted 4 months ago by TheLugal@lemmy.world to c/commandline@programming.dev
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I have a list containing a set of tags, and would like to exclude one tag, unless another tag exists in the line.

Say I have the following list, and want to exclude B, unless A is present.

[A,B]
[A,C]
[B,C]
[A]
[B]

I can reverse grep for B:

> grep --invert-match "B"
[A,C]
[A]

How can I find the previous list, but also the item containing [A,B]?

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[-] borf@lemmynsfw.com 7 points 4 months ago

I like to use awk instead of grep wherever possible, especially for weird logic like this.

awk '!/B/ || /A.*B/' is one way to skin that cat. If you don't care what order A and B are in on the lines containing both, then awk '!/B/ || (/A/ && /B/)' will work.

[-] TheLugal@lemmy.world 1 points 4 months ago

Thank you! This was exactly was I was looking for. :)

this post was submitted on 15 Feb 2024
16 points (94.4% liked)

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