csv, object.size. wc , :
top.size <- object.size(read.csv("simulations.csv", nrow=1000))
lines <- as.numeric(gsub("[^0-9]", "", system("wc -l simulations.csv", intern=T)))
size.estimate <- lines / 1000 * top.size
, , , size.estimate csv; , top.size. , , 1000 .