mbrannigan

############################################
# Instance info
############################################
INSTANCE_ID=$(/usr/bin/curl -s http://169.254.169.254/latest/meta-data/instance-id)
EC2_AVAIL_ZONE=`/usr/bin/curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone`
REGION="`echo \"$EC2_AVAIL_ZONE\" | /bin/sed -e 's:\([0-9][0-9]*\)[a-z]*\$:\\1:'`"
ENI_ID="${ENI_ID}"                                   # have terraform or whatever you're using provide this
ENI_IP=$(/usr/bin/aws ec2 describe-network-interfaces --region=${REGION} | \
    /usr/bin/jq -cr --arg i "${ENI_ID}" '.NetworkInterfaces[]|select(.NetworkInterfaceId==$i).PrivateIpAddress')
NETCIDR="${ENI_IP%.*}.0/24"                          # yeah, it's defaults for my network, put in whatever it is for you

nickjacob

[Unit]
Description=Demonstrate Bash

[Service]
ExecStartPre=/usr/bin/bash -c "/usr/bin/systemctl set-environment MYVAR=$(( 2 + 2 ))"
ExecStart=/usr/bin/echo "2 + 2 = ${MYVAR}"