y-localhost

#!/usr/bin/env bash
[ -z "$DEBUG" ] || set -x
set -eo pipefail

[ "$1" = "help" ] && echo '
Tries to bring up a loopback interface so port bindings can be done without conflicts
' && exit 0

hostname=$1

[ -z "$hostname" ] && echo "First arg must be a hostname" && exit 1

platform="$(uname -s)"

ip=$(cat /etc/hosts | grep -e "[[:blank:]]\<$hostname\>" | awk '{ print $1 }')
[ -z "$ip" ] && >&2 echo "Host '$hostname' not found in /etc/hosts" && exit 1

[ "$2" = "show" ] && echo -n "$ip" && exit 0

num=$(echo -n $ip | cut -d '.' -f 4)

case "$platform" in
  Darwin)
    ifconfig lo0 | grep $ip > /dev/null && exit 0
    echo "Loopback alias for $ip $hostname not found. Will try to create ..."
    [ $(id -u) -eq 0 ] || exec sudo -E $0 "$@"
    ifconfig lo0 alias $ip up
    ;;
  Linux)
    if [ -z "$(ip addr show dev lo label lo:$num)" ]; then
      echo "Adding missing interface lo:$num ..."
      ip addr add $ip/32 dev lo label lo:$num
    fi
    ;;
  *)
    echo "Unsupported platform $platform" && exit 1
    ;;
esac