Bash script to get ec2 instance-id from ecs service

ecs.sh

#!/usr/bin/env bash

ENV=dev

AWS_PROFILE=${ENV}
CLUSTER=${ENV}-cluster

if [[ -z $1 ]]; then
  echo "USAGE: $0 service-keyword"
  exit 1
fi

echo "CLUSTER: ${CLUSTER}"

SERVICE=($(aws ecs list-services --cluster ${CLUSTER} | jq -r '.serviceArns[]' | grep $1))
echo "SERVICE:"
printf '%s\n' "${SERVICE[@]}"

if [[ ${#SERVICE[@]} -ne 1 ]]; then
  echo "Mutiple services found. Quit..."
  exit 1
fi

TASKS=($(aws ecs list-tasks --cluster ${CLUSTER} --service-name ${SERVICE[0]} | jq -r '.taskArns[]'))

# If the output may contain spaces
# while IFS= read -r line; do
#   TASKS+=( "$line" )
# done < <( aws ecs list-tasks --cluster ${CLUSTER} --service-name ${SERVICE} | jq -r '.taskArns[]' )

# If bash 4 is available
#mapfile -t TASKS < <( aws ecs list-tasks --cluster ${CLUSTER} --service-name ${SERVICE} | jq -r '.taskArns[]' )

echo "TASKS:"
printf '%s\n' "${TASKS[@]}"

CONTAINER_INSTANCES=($(aws ecs describe-tasks --cluster ${CLUSTER} --tasks ${TASKS[@]} | jq -r '.tasks[].containerInstanceArn'))

echo "CONTAINER_INSTANCES:"
printf '%s\n' "${CONTAINER_INSTANCES[@]}"

EC2_INSTANCES=$(aws ecs describe-container-instances --cluster ${CLUSTER} --container-instances ${CONTAINER_INSTANCES[@]} | jq -r '.containerInstances[].ec2InstanceId')

echo "EC2_INSTANCES:"
printf '%s\n' "${EC2_INSTANCES[@]}"