file-constants.md

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Learn more about: File Constants	File Constants	11/04/2016	_O_EXCL _O_RDWR _O_APPEND _O_RDONLY _O_TRUNC _O_CREAT _O_WRONLY	_O_RDWR constant O_EXCL constant O_RDWR constant O_WRONLY constant O_APPEND constant O_CREAT constant _O_CREAT constant _O_APPEND constant _O_EXCL constant O_TRUNC constant _O_RDONLY constant _O_TRUNC constant O_RDONLY constant _O_WRONLY constant	c8fa5548-9ac2-4217-801d-eb45e86f2fa4

File Constants

Syntax

#include <fcntl.h>

Remarks

The integer expression formed from one or more of these constants determines the type of reading or writing operations permitted. It is formed by combining one or more constants with a translation-mode constant.

The file constants are as follows:

Constant	Description
_O_APPEND	Repositions the file pointer to the end of the file before every write operation.
_O_CREAT	Creates and opens a new file for writing; this has no effect if the file specified by filename exists.
_O_EXCL	Returns an error value if the file specified by filename exists. Only applies when used with _O_CREAT.
_O_RDONLY	Opens file for reading only; if this flag is given, neither _O_RDWR nor _O_WRONLY can be given.
_O_RDWR	Opens file for both reading and writing; if this flag is given, neither _O_RDONLY nor _O_WRONLY can be given.
_O_TRUNC	Opens and truncates an existing file to zero length; the file must have write permission. The contents of the file are destroyed. If this flag is given, you cannot specify _O_RDONLY.
_O_WRONLY	Opens file for writing only; if this flag is given, neither _O_RDONLY nor _O_RDWR can be given.

See also

_open, _wopen
_sopen, _wsopen
Global Constants