jq - Extract nested properties from an array of objects

Question

I have the following JSON file :

{
  "filter": [
    {
      "id": "id_1",
      "criteria": {
        "from": "mail@domain1.com",
        "subject": "subject_1"
      },
      "action": {
        "addLabelIds": [
          "Label_id_1"
        ],
        "removeLabelIds": [
          "INBOX",
          "SPAM"
        ]
      }
    },
    {
      "id": "id_2",
      "criteria": {
        "from": "mail@domain2.com",
        "subject": "subject_1"
      },
      "action": {
        "addLabelIds": [
          "Label_id_2"
        ],
        "removeLabelIds": [
          "INBOX",
          "SPAM"
        ]
      }
    }
  ]
}

And I would like to extract emails values : mail@domain1.com and mail@domain2.com

I have tried this command:

jq --raw-output '.filter[] | select(.criteria.from | test("mail"; "i")) | .id'

But does not work, I get this error :

jq: error (at <stdin>:1206): null (null) cannot be matched, as it is
not a string exit status 5

Another point : how to display the value of "id" key, where "from" key value = mail@domain1.com ?

So in my file id = id_1

Do you have an idea ?

Answer 1

If you only need to extract the emails from .criteria.from then this filter is enough as far as I can tell:

jq --raw-output '.filter[].criteria.from' file.json

If some objects don't have a criteria object then you can filter out nulls with:

jq --raw-output '.filter[].criteria.from | select(. != null)' file.json

If you want to keep the emails equal to "mail@domain1.com":

jq --raw-output '.filter[].criteria.from | select(. == "mail@domain1.com")' file.json

If you want to keep the emails that start with "mail@":

jq --raw-output '.filter[].criteria.from | select(. != null) | select(startswith("mail@"))' file.json