Hack: Set a variable from a trigger in Vagrant

README.md

I can't seem to set a variable from a trigger which would be used by a provisioner. Here's a really ugly hack that seems to work.

Vagrantfile

# -*- mode: ruby -*-
# vi: set ft=ruby :

require 'pp'


Vagrant.configure("2") do |config|
  config.vm.box = "ubuntu/bionic64"
  
  vagrant_dir=File.dirname(__FILE__)
  host_temp_dir = "#{vagrant_dir}/temp"
  
  puts "create temp directory, where var files will be stored"
  Dir.mkdir(host_temp_dir) unless File.exists?(host_temp_dir)
  puts "create a placeholder var file"
  File.open("#{host_temp_dir}/local_dump_path_name.var.txt", "w") {
    |file| file.puts "default value"
  }

  config.trigger.before [:up, :provision] do |trigger|
    trigger.ruby do |env, machine|
      puts "executing trigger and rewriting value of var file"
      File.open("#{host_temp_dir}/local_dump_path_name.var.txt", "w") {
        |file| file.puts "value set in trigger"
      }
    end
  end
  
  # doesn't work. gets default value
  config.vm.provision "read_var_from_trigger_on_host",
    type: "shell",
    privileged: false,
    inline: "echo '#{File.read("#{host_temp_dir}/local_dump_path_name.var.txt")}'"
  
  # works. gets "value set in trigger"
  config.vm.provision "read_var_from_trigger_on_vm",
    type: "shell",
    privileged: false,
    inline: "echo \"$(head -n 1 /vagrant/temp/local_dump_path_name.var.txt)\""

end

z_output.txt

$ vagrant up --provision
create temp directory, where var files will be stored
create a placeholder var file
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Running action triggers before up ...
==> default: Running trigger...
executing trigger and rewriting value of var file
==> default: Checking if box 'ubuntu/bionic64' version '20190705.0.0' is up to date...
==> default: Running provisioner: read_var_from_trigger_on_host (shell)...
    default: Running: inline script
    default: default value
==> default: Running provisioner: read_var_from_trigger_on_vm (shell)...
    default: Running: inline script
    default: value set in trigger