json - Recursive search values by key

Question

I have a JSON like this:

{ 
  "A": { "error": null },
  "B": { "C": {"error": "error string"}},
  "C": { "D": {"error": null}},
  "D": { "error": "err str"}
}

end I want to find all values of error keys which are not null.

For my example it should return

"error string"
"err str"

How can I do it? Is it possible with jq?

Answer 1

Use .. to iterate recursively, and get all the .error values. If they're null, remove them:

jq '.. | .error? // empty'

Alternatively, instead of using empty you can select the elements that are strings with strings:

jq '.. | .error? | strings'