Any sane way to renice a process by path, every time it is started?

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http://www.linuxquestions.org – Say you have a situation where you want a given program to always run at a certain niceness, regardless of who invokes it or how. What's a sensible way to do this? verynice would probably work, but seems like enormous overkill; and using a cron job would be... well, not very sensible. What I'd like to do is write a script that watches continuously for the start of some process, renices it *once* as soon as it is launched, and then leaves it alone. What methods are available for checking on processes this way? (HowTos)