title: Ansible vars at an inventory file level
body: <p>I understand that we can have vars for particular hosts, and particular groups, how would I idiomatically do the same on a per inventory file basis. </p>
  
  <p>I have 3 inventory files for dev/staging/prod. What is the best way to set vars for these environments. examples would be the stage itself, to be set into <code>/etc/environment</code> for rails, or API keys, or etc. </p>
  
  <p>At this point I have 1 host per env, so I can just set it as host vars, but eventually I wouldn’t be able to scale that.. so I figure there has to be a better way?</p>