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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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.
1 point
