CODEWITHSUNDEEP
jsonjq
David Gard
David Gard

Reputation: 12047

JQ filter returns 'false' when key is not hardcoded

When using JQ to test the value of a key, the filter is unexpectantly returning false when it expected to instead return true.

Assume the following variables -

TAGS='{"kubernetes.io/cluster/my-cluster":"owned"}
CLUSTER_NAME="my-cluster"

When testing $TAGS using a hardcoded value the filter returns true, as expected.

echo $TAGS | jq '."kubernetes.io/cluster/my-cluster" == "owned"'

However, after introducing clusterName as a JQ argument, the filter now returns false.

echo $TAGS | jq --arg clusterName $CLUSTER_NAME '."kubernetes.io/cluster/" + $clusterName == "owned"'

I first wondered if the - in the $CLUSTER_NAME was the issue, but removing that (and updating $TAGS to match) yields the same result.

I've tried the following in the filter, all of which also yield the same result.

."kubernetes.io/cluster/" + "$clusterName"
."kubernetes.io/cluster/ + $clusterName"
."kubernetes.io/cluster/$clusterName"

How can the filter be amended to work as expected?

Upvotes: 0

Views: 85

Answers (1)

0stone0
0stone0

Reputation: 43904

You can use string interpolation (\()) docs to concat that variable to the rest like so:

'."kubernetes.io/cluster/\($clusterName)" == "owned"'

echo $TAGS | jq --arg clusterName $CLUSTER_NAME '."kubernetes.io/cluster/\($clusterName)" == "owned"'

Shows true when testing with the supplied variables.

That said, I'd recommend using here-string (<<<) instead off echo | like so:

$ TAGS='{"kubernetes.io/cluster/my-cluster":"owned"}'
$ CLUSTER_NAME="my-cluster"
$
$ jq --arg clusterName $CLUSTER_NAME '."kubernetes.io/cluster/\($clusterName)" == "owned"' <<< "$TAGS"
true
$

Can I pass a string variable to jq not the file?

Upvotes: 3

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