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Associates a C run-time file descriptor with an existing operating-system file handle.

int _open_osfhandle (
   intptr_t osfhandle,
      int flags 



Operating-system file handle.


Types of operations allowed.

If successful, _open_osfhandle returns a C run-time file descriptor. Otherwise, it returns –1.

The _open_osfhandle function allocates a C run-time file descriptor and associates it with the operating-system file handle specified by osfhandle. The flags argument is an integer expression formed from one or more of the manifest constants defined in Fcntl.h. When two or more manifest constants are used to form the flags argument, the constants are combined with the bitwise-OR operator ( | ).

Fcntl.h defines the following manifest constants.


Positions a file pointer to the end of the file before every write operation.


Opens the file for reading only.


Opens the file in text (translated) mode.

To close a file opened with _open_osfhandle, call _close. The underlying handle is also closed by a call to _close, so it is not necessary to call the Win32 function CloseHandle on the original handle.

Routine Required header Compatibility



Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

For more compatibility information, see Compatibility in the Introduction.


All versions of the C run-time libraries.

© 2015 Microsoft