[R] invoking user-defined function

[Kinoko]

Dear list,

Can somebody tell me how to invoke user-defined functions from script
files during run-time?
Basically I have (almost) one function per script file.

I am thinking of something like

#include   in C++
import      in Java/Python
use          in Perl

No, I don't need my functions every time R is started.
Neither I am thinking about writing building my functions into
packages.
I just want to reference my functions during batch processing.
That's all.

Thanks in advance.

g