jq json - select by key name

Question

I'm using jq to try to parse some details from an AWS CLI query.
Example JSON:

                    "Tags": [
                        {
                            "Key": "Name",
                            "Value": "db01"
                        },
                        {
                            "Key": "BackupResourceType",
                            "Value": "EC2"
                        },
                        {
                            "Key": "Role",
                            "Value": "db_edi01"
                        },
                        {
                            "Key": "OS",
                            "Value": "Ubuntu 18.04"
                        }
                    ],

The issue I'm running into is these tag values aren't in a consistent order. Is there a way I can select the value where key=OS instead of selecting the specific array value?

[.InstanceId, .State.Name, .Tags[1].Value, .Tags[0].Value, etc]

Thanks for the help!

Answer 1

Perhaps the niftiest way would be to use from_entries. E.g. for the "OS" key:

.Tags | from_entries | .OS

More generally, but more verbosely, you could go with:

.Tags | first( .[] | select(.Key == "OS") | .Value)

or if you're concerned about the result if the specified key is not present:

.Tags | first( .[] | select(.Key == "OS") // {} | .Value)

---

Without seeing a complete sample, it's hard to say exactly what the most economical expression would be, but piggy-backing off your example, you could go with something like:

[.InstanceId, .State.Name] +
 [.Tags | from_entries | (.OS, .Role)]