"splunk offline" command prompts for username and password. How to bypass it without providing the password in an rc script?

Hello, I am trying to setup a rc script on our indexer so that Splunk does 'splunk offline' whenever the indexer is being shutdown or rebooted. Issue is, when 'splunk offline' is issued, it is prompting for username and password. I know I can provide `-auth admin:password`, but then I end up hard coding that in my rc script. Is there some other way? Thanks, Simon Mandy