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File Constants 


#include <fcntl.h>

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:

_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.

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