config-exec

config-exec.rb

#!/usr/local/bin/ruby
#
# config-exec will render any files in /config and then exec
# whatever command was given on the command line.
#
# For example, if /config/etc/redis.conf.erb exists, then to
# render it into /etc/redis.conf and run Redis with the result:
#
# $ config-exec redis-server /etc/redis.conf

require "erb"
require "fileutils"

# Any ERB files in this directory will be rendered like so:
#
# /config/etc/foo/bar.conf.erb -> rendered -> /etc/foo/bar.conf
dir = "/config"

Dir["#{dir}/**/*.erb"].each do |source|
  # strip the dir prefix and the .erb extension
  destination = source[%r{#{dir}/(.*).erb}, 1]

  # render the config file
  content = ERB.new(File.read(source)).result

  # write the result to the filesystem
  FileUtils.mkdir_p File.dirname(destination)
  File.open(destination, "w") { |f| f.write content }
end

# exec whatever command we were given on the command line
exec *ARGV