Bash script to replace all ASG instances (by flagging them as Unhealthy, ASG does the rest)

replace-asg-instances.sh

#!/bin/bash

# Usage `./replace-asg-instances.sh my-asg-name`
# Will set all instances to Unhealthy, so they are replaced by the ASG.
# Notice this is meant to work with EC2 health-check ASG, not ELB health-checks.

if [[ $1 == "" ]]; then
    echo Usage "./replace-asg-instances.sh my-asg-name"
    exit 1
fi

aws autoscaling describe-auto-scaling-groups | \
    jq -r ".AutoScalingGroups[] | select (.AutoScalingGroupName | contains(\"$1\"))| .Instances[].InstanceId" | \
    xargs -n1 -I {} \
    aws autoscaling set-instance-health --cli-input-json '{"InstanceId": "{}", "HealthStatus": "Unhealthy"}'