On the login screen, Can users have a choice to select one of the three environments by using radio button or a dropdown list?
More desired info: 1.1. On the login screen, user will have a choice to select one of the three environments by using radio button or a dropdown list. 1.2. This choice will then set a session variable for the user 1.3. This session variable will be used by all the queries of our application. 1.4. In PROD, since we have single server, we can hardcode this session variable to PROD.
it sounds to me like you want to set up different applications, (dashboards, indexes etc) for different users. That can be done, but not by radio buttons..
Still, as Simeon says your question is a bit unclear..
So, what, when someone logs in, they get this set and every query gets "index=blah" added to it? No. Even if you can get the login screen working (that's probably not that hard with 4.1 SSO integration), there's not a good general way to do the latter part.
Upgrades to Splunk now allow the functionality that @gkanapathy described as not possible before. Now you can set a user's role to a default/limited search string with:
access controls ->
roles -> "some role" ->
Restrict search terms.