An R solution is: allocateFile <- function(pathname, nbrOfBytes) { con <- file(pathname, open="wb"); on.exit(close(con)); seek(con, where=nbrOfBytes-1L, origin="start", rw="write"); writeBin(as.raw(0), con=con); invisible(pathname); } # allocateFile()
> allocateFile("foo.bin", nbrOfBytes=985403) > file.info("foo.bin")$size [1] 985403 Note sure if it works on all OSes/file systems. /Henrik On Wed, May 2, 2012 at 3:23 PM, Jonathan Greenberg <j...@illinois.edu> wrote: > R-helpers: > > What would be the absolute fastest way to make a large "empty" file (e.g. > filled with all zeroes) on disk, given a byte size and a given number > number of empty values. I know I can use writeBin, but the "object" in > this case may be far too large to store in main memory. I'm asking because > I'm going to use this file in conjunction with mmap to do parallel writes > to this file. Say, I want to create a blank file of 10,000 floating point > numbers. > > Thanks! > > --j > > -- > Jonathan A. Greenberg, PhD > Assistant Professor > Department of Geography and Geographic Information Science > University of Illinois at Urbana-Champaign > 607 South Mathews Avenue, MC 150 > Urbana, IL 61801 > Phone: 415-763-5476 > AIM: jgrn307, MSN: jgrn...@hotmail.com, Gchat: jgrn307, Skype: jgrn3007 > http://www.geog.illinois.edu/people/JonathanGreenberg.html > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.