Allow specific bots

[daniel_c Profile]

This might be very stupid question, but I have not been able to figure this out.
I've seen several examples in this forum on how to block bad bots.
My question is that, how to do the reverse? Allow only specific bots?

So, instead of blocking bots "A" to "Z", I just want to allow, for example: google-bot, bing-bot, and yahoo-slurp.

Any example would be greatly appreciated.