How to get the unique keys from attributes key with JQ
{"id":1, "attributes":{"a": 1, "b": 2, "c": 3}}
{"id":2, "attributes":{"a": 4, "b": 5, "d": 6}}
{"id":3, "name":"ABC"}
Result like this [ "a", "b", "c", "d" ]
I'm try like this
jq '.attributes' test.json | jq -r '[inputs | keys[]] | unique | sort'
or
jq -r '[inputs.attributes | keys[]] | unique | sort' test.json
but getting error
jq: error (at :11): null (null) has no keys
One way could be using reduce on subsequent inputs:
jq 'reduce inputs.attributes as $a (.attributes; . + $a) | keys'
[
"a",
"b",
"c",
"d"
]
Along the lines of your second attempt:
jq -n '[inputs.attributes // empty | keys_unsorted[]] | unique'
The important point is that we have to take care of the case where there is no "attributes" key.
Note also that unique sorts, so (unless you're using gojq) we can use keys_unsorted to avoid redundant sorting.