jq: error (at <stdin>:0): Cannot iterate over null (null)

Question

I've been working with an API call to structure it in JSON format so I might later push it into a database. Then code looks like this:

getPage() {
curl --fail -X GET 'https://api.app.com/v1/test?page=1&pageSize=1000&sort=desc' \
  -H 'Authorization: Bearer 123abc456pickupsticks789' \
  -H 'cache-control: no-cache'  
}

getPage \
| jq -c '.items | .[] | {landing_id: .landing_id, submitted_at: .submitted_at, answers: .answers, email: .hidden.email}' \
  > testpush.json

When I run it though, it produces this error: jq: error (at <stdin>:0): Cannot iterate over null (null)

I've looked at solutions such as this one, or this one from this site, and this response.

The common solution seemed to be using a ? in front of [] and I tried it in the jq line towards the bottom, but it still does not work. It just produces an empty json file.

Am I misreading the takeaway from those other answers and not putting my ? in the right place?>

Answer 1

To protect against the possibility that .items is not an array, you could write:

.items | .[]?

or even more robustly:

try .items[]

which is equivalent to (.items[])?.

In summary:

• try E is equivalent to try E catch empty
• try E is equivalent to (E)?

(Note that the expressions .items[]? and (.items[])? are not identical.)

However none of these will provide protection against input that is invalid JSON.

---

p.s. In future, please follow the mcve guidelines (http://stackoverflow.com/help/mcve); in the present case, it would have helped if you had provided an illustrative JSON snippet based on the output produced by the curl command.