a very basic question: calling c function from R

Dear R users,

I want to call C function from R. I follow the following instruction using the example of foo.c
http://www.stat.umn.edu/~charlie/rc/

I save the foo.c in my current directory. Is that right? After I enter the command R CMD SHLIB foo.c, I get the following message



Error: unexpected symbol in "R cmd"



Any suggestion is appreciated.



Chun