If you'd like to use something like this in your own APIs to let your clients filter requests or on the CLI (as is the intention with gron), consider giving "json-mask" a try (you'll need Node.js installed):

  $ echo '{"user": {"name": "Sam", "age": 40}}' | npx json-mask "user/age"
  {"user":{"age":40}}

or (from the first gron example; the results are identical)

  $ gron "https://api.github.com/repos/tomnomnom/gron/commits?per_page=1" | fgrep "commit.author" | gron --ungron
  $ curl "https://api.github.com/repos/tomnomnom/gron/commits?per_page=1" | npx json-mask "commit/author"

If you've ever used Google APIs' `fields=` query param you already know how to use json-mask; it's super simple:

  a,b,c - comma-separated list will select multiple fields
  a/b/c - path will select a field from its parent
  a(b,c) - sub-selection will select many fields from a parent
  a/*/c - the star * wildcard will select all items in a field