cpp/experimental/fs/permissions

Changes access permissions of the file to which resolves, as if by POSIX fchmodat. Symlinks are followed if is set.

The effects depend on as follows:


 * If neither nor  is set, file permissions are set to exactly  (meaning, every valid bit of  is applied)
 * If, the file permissions are set to exactly (meaning, any valid bit that is set in , but not in the file's current permissions is added to the file's permissions)
 * If is set, the file permissions are set to exactly  (meaning, any valid bit that is clear in, but set in the file's current permissions is cleared in the file's permissions)
 * If both and  are set, error occurs

The non-throwing overload has no special action on error.

Return value
(none)