```ruby
module SampleVagrantPlugin
  class Command < Vagrant.plugin("2", "command")
    def execute
      machine = @env.machine(:default, :virtualbox)
      if machine.state.id != :running
        @env.ui.error("Machine must be running.")
        return 1
      end

      return 0
    end
  end
end
```

Implement reading the amount of free memory available
user
```ruby
module SampleVagrantPlugin
  class Command < Vagrant.plugin("2", "command")
    def execute
      machine = @env.machine(:default, :virtualbox)
      if machine.state.id != :running
        @env.ui.error("Machine must be running.")
        return 1
      end

      command = "grep MemFree /proc/meminfo | awk '{print $2}'"
      machine.communicate.execute(command) do |type, data|
        @env.ui.info(data)
      end

      return 0
    end
  end
end
```
assistant