# 1. Find the latest ID of the AMI:
NEW_AMI_ID=$(aws ec2 describe-images \
 --filters Name=name,Values=*WHATEVER AMI NAME YOU ARE LOOKING FOR* \
 --query 'Images[*].[ImageId,CreationDate]' \
 --output text | sort -k2 -r | head -n1 | awk {'print $1'})

# 2. Modify a PARAMETERS.vars.json that is being used by AWS CLI in step 3.:
tmp=$(mktemp)
jq -r '[ .[] | select(.ParameterKey=="AmiId").ParameterValue |= '\"$NEW_AMI_ID\"' ]' \
 PARAMETERS.vars.json > "$tmp" && mv "$tmp" PARAMETERS.vars.json

# 3. Create a stack using the above file with the latest AMI ID:
AWS_PROFILE=test aws cloudformation create-stack \
--stack-name WHATEVER \
--template-body file://WHATEVER.template.yaml \
--tags Key=BLA,Value=BLA \
--parameters file://PARAMETERS.vars.json \
--capabilities CAPABILITY_NAMED_IAM \
--profile ${AWS_PROFILE}