How to include (source) R script in other scripts
Solution 1:
Here is one possible way. Use the exists function to check for something unique in your util.R code.
For example:
if(!exists("foo", mode="function")) source("util.R")
(Edited to include mode="function", as Gavin Simpson pointed out)
Solution 2:
There is no such thing built-in, since R does not track calls to source and is not able to figure out what was loaded from where (this is not the case when using packages). Yet, you may use same idea as in C .h files, i.e. wrap the whole in:
if(!exists('util_R')){
util_R<-T
#Code
}