load new files in directory

I have a R script to load multiple text files in a directory and save the data as compressed .rda. It looks like this, ``` #!/usr/bin/Rscript --vanilla args <- commandArgs(TRUE) ## arg[1] is the folder name outname <- paste(args[1], ".rda", sep="") files <- list.files(path=args[1], pattern=".txt", full=TRUE) tmp <- list() if(file.exists(outname)){ message("found ", outname) load(outname) tmp <- get(args[1]) # previously read stuff files <- setdiff(files, names(tmp)) } if(is.null(files)) message("no new files") else { ## read the files into a list of matrices results <- plyr::llply(files, read.table, .progress="text") names(results) <- files assign(args[1], c(tmp, results)) message("now saving... ", args[1]) save(list=args[1], file=outname) } message("all done!") ``` The files are quite large (15Mb each, 50 of them typically), so running this script takes up to a few minutes typically, a substantial part of which is taken writing the .rda results. I often update the directory with new data files, therefore I would like to append them to the previously saved and compressed data. This is what I do above by checking if there's already an output file with that name. The last step is still pretty slow, saving the .rda file. Is there a smarter way to go about this in some package, keeping a trace of which files have been read, and saving this faster? I saw that `knitr` uses `tools:::makeLazyLoadDB` to save its cached computations, but this function is not documented so I'm not sure where it makes sense to use it.