In R, what is the difference between unlink and file.remove?

Question

R provides two functions to remove files (and folder) from the file system:

• unlink
• file.remove

It's not entirely obvious what the differences are, or indeed when to use which, other than that unlink takes some additional arguments.

Reading the source code for these functions doesn't help very much, since both simply calls a compiled C function.

What are the differences? When should you use unlink in preference to file.remove, or vice versa?

Answer 1

My guess is simply that unlink was present in S, since it references Becker, Chambers and Wilks (1988), whereas file.remove (and file.copy, file.create, etc.) have been part of R since early on in order to provide a family of functions for general file manipulation.

unlink corresponds to a very old Unix function (and certainly existed when the 1988 version of S appeared): http://en.wikipedia.org/wiki/Unlink_(Unix)

So, unlink is there for compatibility with S, file.remove is there as a part of R and both are maintained in order to support long existing code from S and R. Other than that simply choose the one that suits your needs (or habits) best.

Answer 2

I believe that the main practical difference in the behaviour of the functions is how they handle a file that is currently open, and thus which cannot be immediately deleted:

• unlink() marks the file for deletion as soon as it is not open in any other context;
• file.remove() leaves the file intact, returning FALSE, but throws a warning.

Related: how to remove the file when "permisson denied" in R?