Transforming nested array of objects using jq

Question

How can I transform the JSON input

{
"Subnets": [
    {
        "VpcId": "vpc-xxx",
        "Tags": [
            {
                "Value": "staging_subnet_private_a",
                "Key": "Name"
            }
        ],
        "SubnetId": "subnet-xxx"
    },
    ...
    ]
}

to

[
 {
  "SubnetId": "subnet-xxx",
  "Name": "staging_subnet_private_a"
 },
 ...
]

using jq?

I have a working solution using jq '[.Subnets[] | {SubnetId, Name: .Tags[0] | .Value }]', but this relies on the order of Tags (not good).

Could I use from_entires or reduce maybe?

score 5 · Accepted Answer · 2015-08-01 18:58:23Z

5

Yes, you could use from_entries. In jq 1.5rc1 and above, it is defined as taking Key/Value key names as well as key/value.

Try something like:

jq '.Subnets | map({SubnetId} + (.Tags | from_entries))'

On previous versions, you could modify the "entries" before passing them to from_entries:

jq '.Subnets | map({SubnetId} + (.Tags | map({value: .Value, key: .Key}) | from_entries))'

edited Aug 1, 2015 at 18:58

answered Aug 1, 2015 at 17:32

user3899165

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1 Comment

Jeff Mercado Over a year ago

Depending on the requirements, mapping all tags might include too much. So an additional select call would help limit what's used.

jq170727 · Accepted Answer · 2017-08-25 17:44:23Z

1

Here is a solution which only uses jq primitives.

[
  .Subnets[]
| {SubnetId} + (.Tags[] | if .Key=="Name" then {Name:.Value} else empty end)
]

answered Aug 25, 2017 at 17:44

jq170727

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