Return_Value

   A character string containing the expanded file specification
   or the field you specify. If you do not provide a complete file
   specification for the filespec argument, the F$PARSE function
   supplies defaults in the return string.

   In most cases, the F$PARSE function returns a null string ("")
   if an error is detected during the parse. For example, a null
   string is returned if the file specification has incorrect
   syntax or if a disk or directory does not exist, making the file
   specification logically incorrect. However, when you specify a
   field name or the SYNTAX_ONLY parse type, F$PARSE returns the
   appropriate information.