Construct the path to a file from components in a platform-independent way.
file.path(…, fsep = .Platform$file.sep)character vectors.
the path separator to use.
A character vector of the arguments concatenated term-by-term and
separated by fsep if all arguments have positive length;
otherwise, an empty character vector (unlike paste).
The implementation is designed to be fast (faster than
paste) as this function is used extensively in R itself.
It can also be used for environment paths such as PATH and
R_LIBS with fsep = .Platform$path.sep.
Trailing path separators are invalid for Windows file paths apart from
/ and d:/ (although some functions/utilities do accept
them), so a trailing / or \ is removed.