This small script will keep the password out of the history, however if someone managed to compromise your server and is on it when you start the master node he will be able to see the password anyway in the output of 'ps'
https://gist.github.com/Scriptiee/ab87a739cc6eff4ac516
This is an...
think one of the next updates should address the issue of the password being passed via the command line as raised by vertoe here: http://serverfault.com/q/592744/116529
Have a good look through the bitcointalk and you will see that this topic comes up times and times again. And is explained times and times again. Do some research before asking, don't expect people to do the leg work for you.