Detect empty json values

Question

I'm trying to detect when I get all empty json values.

Here are 2 examples of empty json values.

json='{
  "data": [],
  "pagination": {
    "cursor": ""
  }
}'

json='{
    "data": [],
    "error": "",
    "message": "",
    "status": ""
}'

The closest I've gotten is this, which seems to work for the first example, but not the 2nd.

echo "$json" | jq -e 'all( .[] ; . == "" or . == [] or . == {}  )'

One, I thought easy way, would be to get the string text from each key pair, then just check if I'm left with an empty string. But I haven't found a way that works in the pagination example.

That is a possibility, but I was hoping there was a more compact solution. — Mint
– Mint, Commented Sep 27, 2022 at 14:44

pmf · Accepted Answer · 2022-09-27 14:47:52Z

1

This will give you false if all strings and arrays are "" or []:

jq -e 'all(.. | strings, arrays; IN("", [])) | not'

Demo

answered Sep 27, 2022 at 14:47

pmf

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2 Comments

Mint Over a year ago

This is exactly what I was after! Thank you so much.

pmf Over a year ago

Note: Applying De Morgan's laws, the filter can also be expressed using any by bringing not inside to act on IN: any(.. | strings, arrays; IN("", []) | not)

glenn jackman · Accepted Answer · 2022-09-27 16:24:09Z

1

This might be a good use for gron

json='{
  "data": [],
  "pagination": {
    "cursor": "",
    "position":[2,3]
  }
}'

gron transforms the input JSON into discrete paths:

$ gron <<< "$json"
json = {};
json.data = [];
json.pagination = {};
json.pagination.cursor = "";
json.pagination.position = [];
json.pagination.position[0] = 2;
json.pagination.position[1] = 3;

and to test for any non-empty elements

$ gron <<< "$json" | grep -Evq '(\{\}|\[\]|"");$' && echo "not everything is empty"
not everything is empty

answered Sep 27, 2022 at 16:24

glenn jackman

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1 Comment

Mint Over a year ago

Oh wow, gron is pretty cool, learn something new every day!

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