[R] How to return/show the indexes of unusual points in boxplot?

[guox at ucalgary.ca]

I am wondering if you know how to return by function or show in boxplot,
the indexes of unusual points, such as,
points that are outside the box or in [Q3+1.5IQR,Max].
For example,

> boxplot(c(4,rnorm(20),8))

There are 2 unusual points 4 and 8. How to show the indexes of 4 and 8 in
the boxplot
or return them by function?

Thanks,

-james