In http://www.esva.net/~beman/filesystem_operations_predicates.htm, the assumptions was that file system entities are either files or directories. But an operating system might support additional file system entities which can only be accessed via a specific API, and can't be accessed via fstreams or directory_iterators. For example, on some operating systems, sockets are file system entities and may be found during directory iterations, but can't be opened as either directories or fstreams. What to do? Possibilities: 1) Add an other_flag and a matching is_other() function. Change definition of exists() to status() & (directory_flag|file_flag|other_flag) 2) Try to identify specific other types like sockets, and define flags and predicate functions for each. Handle future needs by saying an implementation has to define suitable flags and predicate functions for any additional kinds of files. 3) Treat such entities as files. 4) Treat such entities as errors. 5) Treat such entities as not found. To me, (1) seems best. (2) is too open ended, and without a matching API to access the additional types, doesn't do much beyond (1). The others are not acceptable because they are misleading and don't match expectations. Comments? --Beman