GetFileType

GetFileType is a Windows API function used to determine the type of a file handle. It helps programs decide how to handle a given handle without opening or inspecting the underlying object directly.

Signature and parameters

The function is declared as DWORD GetFileType(HANDLE hFile). The hFile parameter must be a valid handle, typically obtained through functions such as CreateFile, CreateFileMapping, or other Windows I/O operations.

Return values

GetFileType returns one of several FILE_TYPE constants:

- FILE_TYPE_DISK for disk files

- FILE_TYPE_CHAR for character devices (such as consoles or serial ports)

- FILE_TYPE_PIPE for named pipes

- FILE_TYPE_UNKNOWN if the type cannot be determined or the handle is invalid

If the return value is FILE_TYPE_UNKNOWN, GetLastError may provide more information about the failure.

Usage notes

GetFileType does not determine whether a path refers to a directory or a regular file; it reports the type of the I/O object associated with the handle. It is often used to route input/output decisions, such as choosing a read path for disk files versus pipes. The function can be called on handles opened for various purposes, including console input, file I/O, or interprocess communication.

See also

Related APIs include CreateFile (to obtain handles), GetLastError (for error details when GetFileType fails), and the FILE_TYPE_* constants defined in Windows headers.

History

GetFileType has been part of the Win32 API for many generations of Windows, providing a lightweight means to classify handles without inspecting file system metadata.

---