[SOLVED] Reading several variables from a single command's multi-line output

Issue

I'm running into an issue with the read command. I'm trying to get read to run through the output of my awscli command to extract VPC_ID, VPC_CIDR and VPC_NAME. Unfortunately its no longer working since upgrading to bash 5.0.

Here is the following code: read VPC_ID VPC_CIDR VPC_NAME <<<$(aws ec2 describe-vpcs --filters "Name=tag:Name,Values=${AWS_PROFILE}-vpc" --output json | jq -r '.Vpcs[] | .VpcId,.CidrBlock, (.Tags[]|select(.Key=="Name")|.Value)')

When I run aws ec2 describe-vpcs --filters "Name=tag:Name,Values=${AWS_PROFILE}-vpc" --output json | jq -r '.Vpcs[] | .VpcId,.CidrBlock, (.Tags[]|select(.Key=="Name")|.Value)'

I get my expected output but when I attached the read command in front of it, I'm only able to assign the first variable none of the other ones...

Solution

The problem is that read, by default, stops at the first newline it sees. (This can be overridden with the -d argument). You can work around this by running a separate read per variable, or running read with a different character used as the record delimiter.

The first approach:

{ read -r VPC_ID && read -r VPC_CIDR && read -r VPC_NAME; } < <(
  aws ec2 describe-vpcs --filters "Name=tag:Name,Values=${AWS_PROFILE}-vpc" --output json \
  | jq -r '.Vpcs[] | .VpcId,.CidrBlock, (.Tags[]|select(.Key=="Name")|.Value)'
)

The second approach, which adds a printf '\0' when the inner command is successful, which read -d '' recognizes to mean the record is complete:

IFS=$'\n' read -r -d '' VPC_ID VPC_CIDR VPC_NAME < <(
  aws ec2 describe-vpcs --filters "Name=tag:Name,Values=${AWS_PROFILE}-vpc" --output json \
  | jq -r '.Vpcs[] | .VpcId,.CidrBlock, (.Tags[]|select(.Key=="Name")|.Value)' \
  && printf '\0'
)

Answered By - Charles Duffy

Answer Checked By - Candace Johnson (WPSolving Volunteer)