How I get values from a JSON document in bash?

Question

I want to write a script that finds my unused volumes in AWS. (the 'status' of used volumes is 'in-use').

When I use the aws ec2 describe-volumes --filters Name=status,Values=available I got the next response for example.

{ "Volumes": [ { "Attachments": [], "AvailabilityZone": "us-east-1a", "CreateTime": "2022-04-21T08:45:29.704000+00:00", "Encrypted": false, "Size": 1, "SnapshotId": "", "State": "available", "VolumeId": "vol-0e81644ad6193439f", "Iops": 100, "Tags": [ { "Key": "sre", "Value": "test" } ], "VolumeType": "gp2", "MultiAttachEnabled": false } ] }

I want to save just the state, volumeId & tags.

Answer 1

Assuming you can't use the aws command to do this, I would personally use the JSON parser jq to extract the wanted data.

jq '.Volumes[] | { State: .State, VolumeId: .VolumeId, Tags: .Tags }'

For each entry in the Volumes array, this would create a new JSON object containing only the fields you want to keep from that entry.

With your given JSON document as input, this would result in

{
  "State": "available",
  "VolumeId": "vol-0e81644ad6193439f",
  "Tags": [
    {
      "Key": "sre",
      "Value": "test"
    }
  ]
}

Or, if you use jq -c:

{"State":"available","VolumeId":"vol-0e81644ad6193439f","Tags":[{"Key":"sre","Value":"test"}]}

... which is an equivalent document.