til/jq/find-all-objects-with-a-matching-key-value-pair.md

Find All Objects With A Matching Key Value Pair

Let's say I have a JSON file representing a bunch of people's reading lists. That means it is an array of objects where each object is a person's reading profile and contains a list of books. Some of those books have a status of reading meaning the person is currently reading that book.

How can we find all books that are currently being read?

jq '. | map(
      {
        name: .username,
        in_progress_books: (.books | map(select(.status == "reading")))
      }
    )'

[
  { name: 'bobr', in_progress_books: [...] },
  { name: 'sallyf', in_progress_books: [...] },
  ...
]

That will show us for each reader what books they are currently reading.

Alternatively, we could roll that all up into a single list of books.

jq '. |
      map(.books | map(select(.status == "reading"))) |
      flatten'

[
  { title: 'Moby Dick', status: 'reading', ... }
  { title: 'The Great Gatsby', status: 'reading', ... }
  ...
]

source