Shell script assigns given private IPv4 addresses (e.g. secondary private IP) to a EC2 instance

ip.sh

if_macs="$(ip -o link show up | grep -v lo: | grep link/ether | sed -re 's|^[0-9]+: (.+?): .+link/ether ([0-9a-f:]+?).*$|\1,\2|')"

for if_mac in $if_macs; do
  ifname="$(echo "$if_mac" | cut -d, -f 1)"
  mac="$(echo "$if_mac" | cut -d, -f 2)"
  ifmeta="http://169.254.169.254/latest/meta-data/network/interfaces/macs/${mac}"

  cidr="$(curl -s ${ifmeta}/subnet-ipv4-cidr-block)"
  netlen="$(echo "$cidr" | cut -d/ -f 2)"

  local_ips="$(curl -s ${ifmeta}/local-ipv4s)"

  for ip in $local_ips; do
    echo "${ip}/${netlen} dev ${ifname}"
    sudo ip addr add ${ip}/${netlen} dev ${ifname}
  done
done