30 Input/output library [input.output]

30.10 File systems [filesystems]

30.10.15 Filesystem operation functions [fs.op.funcs]

30.10.15.35 Status [fs.op.status]

file_status status(const path& p);

Effects: As if:

error_code ec;
file_status result = status(p, ec);
if (result.type() == file_type::none)
  throw filesystem_error(implementation-supplied-message, p, ec);
return result;

Returns: See above.

Throws: filesystem_­error. [Note: result values of file_­status(file_­type​::​not_­found) and file_­status(file_­type​::​unknown) are not considered failures and do not cause an exception to be thrown.end note]

file_status status(const path& p, error_code& ec) noexcept;

Effects: If possible, determines the attributes of the file p resolves to, as if by using POSIX stat() to obtain a POSIX struct stat. If, during attribute determination, the underlying file system API reports an error, sets ec to indicate the specific error reported. Otherwise, ec.clear(). [Note: This allows users to inspect the specifics of underlying API errors even when the value returned by status() is not file_­status(file_­type​::​none). end note]

Let prms denote the result of (m & perms​::​mask), where m is determined as if by converting the st_­mode member of the obtained struct stat to the type perms.

Returns:

  • If ec != error_­code():

    • If the specific error indicates that p cannot be resolved because some element of the path does not exist, returns file_­status(file_­type​::​not_­found).

    • Otherwise, if the specific error indicates that p can be resolved but the attributes cannot be determined, returns file_­status(file_­type​::​unknown).

    • Otherwise, returns file_­status(file_­type​::​none).

    [Note: These semantics distinguish between p being known not to exist, p existing but not being able to determine its attributes, and there being an error that prevents even knowing if p exists. These distinctions are important to some use cases. end note]

  • Otherwise,

    • If the attributes indicate a regular file, as if by POSIX S_­ISREG, returns file_­status(file_­type​::​regular, prms). [Note: file_­type​::​regular implies appropriate <fstream> operations would succeed, assuming no hardware, permission, access, or file system race errors. Lack of file_­type​::​regular does not necessarily imply <fstream> operations would fail on a directory. end note]

    • Otherwise, if the attributes indicate a directory, as if by POSIX S_­ISDIR, returns file_­status(file_­type​::​directory, prms). [Note: file_­type​::​directory implies that calling directory_­iterator(p) would succeed. end note]

    • Otherwise, if the attributes indicate a block special file, as if by POSIX S_­ISBLK, returns file_­status(file_­type​::​block, prms).

    • Otherwise, if the attributes indicate a character special file, as if by POSIX S_­ISCHR, returns file_­status(file_­type​::​character, prms).

    • Otherwise, if the attributes indicate a fifo or pipe file, as if by POSIX S_­ISFIFO, returns file_­status(file_­type​::​fifo, prms).

    • Otherwise, if the attributes indicate a socket, as if by POSIX S_­ISSOCK, returns file_­status(file_­type​::​socket, prms).

    • Otherwise, if the attributes indicate an implementation-defined file type ([fs.enum.file_type]), returns file_­status(file_­type​::​A, prms), where A is the constant for the implementation-defined file type.

    • Otherwise, returns file_­status(file_­type​::​unknown, prms).

Remarks: If a symbolic link is encountered during pathname resolution, pathname resolution continues using the contents of the symbolic link.