Open a file for sharing.
int _sopen( const char *filename, int oflag, int shflag [, int pmode ] ); int _wsopen( const wchar_t *filename, int oflag, int shflag [, int pmode ] );
- Type of operations allowed.
- Type of sharing allowed.
- Permission setting.
Each of these functions returns a file descriptor for the opened file. A return value of –1 indicates an error, in which case errno is set to one of the following values:
- Given path is a directory, or file is read-only, but an open-for-writing operation was attempted.
- _O_CREAT and _O_EXCL flags were specified, but filename already exists.
- Invalid oflag or shflag argument.
- No more file descriptors available.
- File or path not found.
See _doserrno, errno, _sys_errlist, and _sys_nerr for more information on these, and other, return codes.
The _sopen function opens the file specified by filename and prepares the file for shared reading or writing, as defined by oflag and shflag. _wsopen is a wide-character version of _sopen; the filename argument to _wsopen is a wide-character string. _wsopen and _sopen behave identically otherwise.
Generic-Text Routine Mappings
|TCHAR.H routine||_UNICODE & _MBCS not defined||_MBCS defined||_UNICODE defined|
The integer expression oflag is formed by combining one or more of the following manifest constants, defined in the file FCNTL.H. When two or more constants form the argument oflag, they are combined with the bitwise-OR operator ( | ).
- Repositions file pointer to end of file before every write operation.
- Opens file in binary (untranslated) mode. (See fopen for a description of binary mode.)
- Creates and opens new file for writing. Has no effect if file specified by filename exists. The pmode argument is required when _O_CREAT is specified.
- _O_CREAT | _O_SHORT_LIVED
- Create file as temporary and if possible do not flush to disk. The pmode argument is required when _O_CREAT is specified.
- _O_CREAT | _O_TEMPORARY
- Create file as temporary; file is deleted when last file descriptor is closed. The pmode argument is required when _O_CREAT is specified.
- _O_CREAT | _O_EXCL
- Returns error value if file specified by filename exists. Applies only when used with _O_CREAT.
- Prevents creation of a shared file descriptor.
- Specifies primarily random access from disk.
- Opens file for reading only; cannot be specified with _O_RDWR or _O_WRONLY.
- Opens file for both reading and writing; cannot be specified with _O_RDONLY or _O_WRONLY.
- Specifies primarily sequential access from disk
- Opens file in text (translated) mode. (For more information, see Text and Binary Mode File I/O and fopen.)
- Opens file and truncates it to zero length; the file must have write permission. You cannot specify this flag with _O_RDONLY. _O_TRUNC used with _O_CREAT opens an existing file or creates a new file.
Note The _O_TRUNC flag destroys the contents of the specified file.
- Opens file for writing only; cannot be specified with _O_RDONLY or _O_RDWR.
To specify the file access mode, you must specify either _O_RDONLY, _O_RDWR, or _O_WRONLY. There is no default value for the access mode.
The argument shflag is a constant expression consisting of one of the following manifest constants, defined in SHARE.H.
- Denies read and write access to file
- Denies write access to file
- Denies read access to file
- Permits read and write access
The pmode argument is required only when you specify _O_CREAT. If the file does not exist, pmode specifies the file's permission settings, which are set when the new file is closed the first time. Otherwise pmode is ignored. pmode is an integer expression that contains one or both of the manifest constants _S_IWRITE and _S_IREAD, defined in SYS\STAT.H. When both constants are given, they are combined with the bitwise-OR operator. The meaning of pmode is as follows:
- Writing permitted
- Reading permitted
- _S_IREAD | _S_IWRITE
- Reading and writing permitted
If write permission is not given, the file is read-only. Under Windows 98/Me and Windows NT/2000/XP, all files are readable; it is not possible to give write-only permission. Thus the modes _S_IWRITE and _S_IREAD | _S_IWRITE are equivalent.
_sopen applies the current file-permission mask to pmode before setting the permissions (see _umask).
|Routine||Required header||Optional headers||Compatibility|
|_sopen||<io.h>||<fcntl.h>, <sys/types.h>, <sys/stat.h>, <share.h>||Win 98, Win Me, Win NT, Win 2000, Win XP|
|_wsopen||<io.h> or <wchar.h>||<fcntl.h>, <sys/types.h>, <sys/stat.h>, <share.h>||Win NT, Win 2000, Win XP|
For additional compatibility information, see Compatibility in the Introduction.
All versions of the C run-time libraries.
See the example for _locking.