Fully qualified file name in R

Question

I wish to get the fully qualified name of a file in R, given any of the standard notations. For example:

• file.ext
• ~/file.ext (this case can be handled by path.expand)
• ../current_dir/file.ext
• etc.

By fully qualified file name I mean, for example, (on a Unix-like system):

/home/user/some/path/file.ext

(Edited - use file.path and attempt Windows support) A crude implementation might be:

path.qualify <- function(path) {
  path <- path.expand(path)
  if(!grepl("^/|([A-Z|a-z]:)", path)) path <- file.path(getwd(),path)
  path
}

However, I'd ideally like something cross-platform that can handle relative paths with ../, symlinks etc. An R-only solution would be preferred (rather than shell scripting or similar), but I can't find any straightforward way of doing this, short of coding it "from scratch".

Any ideas?

Answer 1

I think you want normalizePath():

> setwd("~/tmp/bar")
> normalizePath("../tmp.R")
[1] "/home/gavin/tmp/tmp.R"
> normalizePath("~/tmp/tmp.R")
[1] "/home/gavin/tmp/tmp.R"
> normalizePath("./foo.R")
[1] "/home/gavin/tmp/bar/foo.R"

For Windows, there is argument winslash which you might want to set all the time as it is ignored on anything other than Windows so won't affect other OSes:

> normalizePath("./foo.R", winslash="\\")
[1] "/home/gavin/tmp/bar/foo.R"

(You need to escape the \ hence the \\) or

> normalizePath("./foo.R", winslash="/")
[1] "/home/gavin/tmp/bar/foo.R"

depending on how you want the path presented/used. The former is the default ("\\") so you could stick with that if it suffices, without needing to set anything explicitly.

On R 2.13.0 then the "~/file.ext" bit also works (see comments):

> normalizePath("~/foo.R")
[1] "/home/gavin/foo.R"

Answer 2

I think I kind of miss the point of your question, but hopefully my answer can point you into the direction you want (it integrates your idea of using paste and getwdwith list.files):

paste(getwd(),substr(list.files(full.names = TRUE), 2,1000), sep ="")

Edit: Works on windows in some tested folders.