Convert file paths to canonical form for the platform, to display them in a user-understandable form and so that relative and absolute paths can be compared.
character vector of file paths.
the separator to be used on Windows – ignored
elsewhere. Must be one of
path.expand) is first done on
Where the Unix-alike platform supports it attempts to turn paths into
absolute paths in their canonical form (no ./, ../ nor
symbolic links). It relies on the POSIX system function
realpath: if the platform does not have that (we know of no
current example) then the result will be an absolute path but might
not be canonical. Even where
realpath is used the canonical
path need not be unique, for example via hard links or
On Windows it converts relative paths to absolute paths, resolves symbolic
links, converts short names for path elements to long names and ensures the
separator is that specified by
winslash. It will match each path
element case-insensitively or case-sensitively as during the usual name
lookup and return the canonical case. It relies on Windows API function
GetFinalPathNameByHandle and in case of an error (such as
insufficient permissions) it currently falls back to the R 3.6 (and
older) implementation, which relies on
GetLongPathName with limitations described in the Notes section.
An attempt is made not to introduce UNC paths in presence of mapped drives
or symbolic links: if
GetFinalPathNameByHandle returns a UNC path,
GetLongPathName returns a path starting with a drive letter, R
falls back to the R 3.6 (and older) implementation.
UTF-8-encoded paths not valid in the current locale can be used.
mustWork = FALSE is useful for expressing paths for use in
A character vector.
If an input is not a real path the result is system-dependent (unless
mustWork = TRUE, when this should be an error). It will be
either the corresponding input element or a transformation of it into
an absolute path.
Converting to an absolute file path can fail for a large number of reasons. The most common are
One of more components of the file path does not exist.
A component before the last is not a directory, or there is insufficient permission to read the directory.
For a relative path, the current directory cannot be determined.
A symbolic link points to a non-existent place or links form a loop.
The canonicalized path would be exceed the maximum supported length of a file path.
The canonical form of paths may not be what you expect. For example,
on macOS absolute paths such as ‘/tmp’ and ‘/var’ are
symbolic links. On Linux, a path produced by bash process substitution is
a symbolic link (such as ‘/proc/fd/63’) to a pipe and there is no
canonical form of such path. In R 3.6 and older on Windows, symlinks will
not be resolved and the long names for path elements will be returned with
the case in which they are in
path, which may not be canonical in
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