How to parse json values stored in shell variable

Question

#!/bin/bash 

DESCRIBE_VPC=$(aws ec2 describe-vpcs --region us-west-2)

The Json value retrieved from aws ec2 describe-vpcs --region us-west-2 stores in DESCRIBE_VPC which comes to the output format below.

> echo $DESCRIBE_VPC

{
    "Vpcs": [
        {
            "VpcId": "vpc-12345678910",
            "InstanceTenancy": "default",
            "Tags": [
                {
                    "Value": "arn:aws:cloudformation:us-west-2:12345678910:stack/vpc/0123456-vpcid",
                    "Key": "stack-id"
                },
                {
                    "Value": "vpc-type",
                    "Key": "Name"
                },
            ],
            "CidrBlockAssociationSet": [
                {
                    "AssociationId": "vpc-cidr-123456",
                    "CidrBlock": "123.456.89.10",
                    "CidrBlockState": {
                        "State": "associated"
                    }
                }
            ],
            "State": "available",
            "DhcpOptionsId": "dpt-01234567",
            "OwnerId": "12345678910",
            "CidrBlock": "123.456.789.10",
            "IsDefault": false
        }
    ]
}

[root@ip bin]# jq '.Vpcs' $DESCRIBE_VPC

jq: error: Could not open file {: No such file or directory
jq: error: Could not open file "Vpcs":: No such file or directory
parse error: Invalid numeric literal at line 1, column 57

Any suggestions here how to parse the json values stored in variable?

thanasisp · Accepted Answer · 2020-09-25 22:11:33Z

1

Actually you have to use the (json) content of a shell variable in place of a command's (jq) input. This input should be a file or a stream, but you have it in a shell variable. There are many ways to do this, this is a simple one:

echo "$DESCRIBE_VPC" | jq '.Vpcs'

or

printf "%s" "$DESCRIBE_VPC" | jq '.Vpcs'

or this (for bash shell):

jq '.Vpcs' <<< "$DESCRIBE_VPC"

Also jq can accept variables and json variables. For example you could do this:

jq -n --argjson x "$DESCRIBE_VPC" '$x.Vpcs'

But the first one is usually better.

edited Sep 25, 2020 at 22:11

answered Sep 25, 2020 at 21:59

thanasisp

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