IP address of docker host (mac) in shell scripts. Only works with #docker for #macos

mac_ip.sh

#!/bin/sh

# Tested on alpine linux
# Thanks to `docker.for.mac.localhost` (or `docker.for.mac.host.internal`)
# featured in https://docs.docker.com/docker-for-mac/networking/#i-want-to-connect-from-a-container-to-a-service-on-the-host,
# it's possible to access host (mac) services

# mac_ip will set IP address (MAC_IP) of mac visible from docker container and
# return code (0 = IP found, 1 = not found)
mac_ip() {
  MAC_IP=`ping -c 1 docker.for.mac.host.internal 2>/dev/null | grep ' from ' | awk -F ' \|:' '{print $4}'`
  [ "${MAC_IP}" != "" ] && return 0 || return 1
}