Stop an R program without error

Question

Is there any way to stop an R program without error?

For example I have a big source, defining several functions and after it there are some calls to the functions.

Answer 1

why not just use an if () {} else {}? It's only a couple of characters...

f1 <- function(){}
f2 <- function(){}

if (justUpdate) {
} else {
# main body 
}

or even

f1 <- function(){}
f2 <- function(){}

if (!justUpdate) {
# main body 
}