DouKaku?

read.file <- function (infile, offset=0){
   con <- file(infile)
   open(con)
   seek(con, offset)
   lines <- readLines(con)
   cur.offset <- seek(con)
   close(con)
   list(l=lines, o=cur.offset)
}

my.tail <- function(infile, n=10, follow=FALSE){
   lines <- read.file(infile)
   writeLines(tail(lines$l, n))
   if(follow){
       size  <- file.info(infile)$size
       repeat{
           if(size < (s <- file.info(infile)$size)){
               lines <- read.file(infile, lines$o)
               writeLines(lines$l)
               size <- s
           }
           Sys.sleep(1)
       }
   }
}