[R] a quick Q: a function in R, equivalent to "atoi" function in C?

[Yan Yu]

Hello,
   I wonder is there a function in R, which can achieve the functionality
of atoi in C, i.e., convert from a character string to a number?

I use Sys.getenv(), it returns a character string, e.g., "12", but i need
a number, e.g., 12, to fit into a function.

thanks a lot,
yan