Ruby shell script to generate nginx.conf from docker containers

nginx.conf.erb

upstream propertypub {
  <% ip_addresses_for_web_containers.each do |ip_address| %>
    server <%= ip_address %>:80;
  <% end %>
}

update-conf

#!/usr/bin/env ruby

require 'erb'

containers = `docker ps`
containers_array = containers.split
containers = containers_array.select { |string| string.include?('app_web_') }

ip_addresses_for_web_containers = []

if !containers.empty?
  containers.each do |c|
    ip_address = `docker inspect #{c} | grep IPAddress | cut -d '"' -f 4`
    ip_address = ip_address.delete("\n")
    ip_addresses_for_web_containers << ip_address
  end
end

conf_template = File.read("nginx.conf.erb")
erb = ERB.new(conf_template)
conf = erb.result(binding)

File.open("nginx.conf", "w") do |file|
  file.puts(conf)
end