Iterate over JSON data for each specific key-CodePudding

I have a JSON with this format:

{
  "instance-01": {
    "instance_aws_az": "eu-west-1a",
    "instance_aws_dns_name": "<ip>eu-west-1.compute.amazonaws.com",
    "instance_ec2_tags": {
      "Name": "2ed97a79c27be6bca883",
      "Serial_number": "22000528",
    },
    "instance_sg_groups": [],
  },
  "instance-29": {
    "instance_aws_az": "eu-west-1a",
    "instance_aws_dns_name": "<ip>eu-west-1.compute.amazonaws.com",
    "instance_ec2_tags": {
      "Name": "2ed97a79c27be6bca773",
      "Serial_number": "22000578",
    },
    "instance_sg_groups": [],
  }
}

So, the main keys are "instance-01" and "instance-29". I can get that info with:

jq -c 'keys[]' instances_metadata.json

However, I want to use the key names I get with that to iterate over the nested info for each one, for example:

jq -c 'keys[]' instances_metadata.json | while read i; do
    echo "Instance $i: Serial Number is: $i.instance_ec2_tags.Serial_number"
    // Edit with more specific tasks I want to run
    if [ "instance-01" = "$i" ]; then
      echo "Instance $i: "
      // Something like that to filter by key.. I tried several options but with no success 
      serial_number=$(jq -r '.[].instance_ec2_tags.Serial_number | select(. == "instance-01")' instances_metadata.json ) 
      echo "Value: $serial_number"
      aws s3 cp .... //using $serial_number and other values
    fi
done

How can I do this? I just found questions to iterate but ignoring which key name it has and in this case I need to have that info inside the loop.

CodePudding user response：

If the task is accomplishable within jq, there's no need for a bash loop and multiple jq calls, as you can do the iteration inside jq using variables with the as notation as in keys[] as $i | …. For example:

jq -r '
  keys[] as $i
  | "Instance \($i): Serial Number is: \(.[$i].instance_ec2_tags.Serial_number)"
'

Instance instance-01: Serial Number is: 22000528
Instance instance-29: Serial Number is: 22000578

Demo

If it is not, then you will have to loop in bash. Introduce the loop variable to the nested jq calls using --arg and reference the according object using it as .[$varname]. Here's your edited example with the modifications mentioned:

jq -r 'keys[]' instances_metadata.json | while read i; do
    echo "Instance $i: Serial Number is: $(jq -r --arg i "$i" '.[$i].instance_ec2_tags.Serial_number' instances_metadata.json)"
    // Edit with more specific tasks I want to run
    if [ "instance-01" = "$i" ]; then
      echo "Instance $i: "
      // Something like that to filter by key.. I tried several options but with no success 
      serial_number="$(jq -r --arg i "$i" '.[$i].instance_ec2_tags.Serial_number' instances_metadata.json)"
      echo "Value: $serial_number"
      aws s3 cp .... //using $serial_number and other values
    fi
done