_sopen, _wsopen

Header File

fcntl.h, sys\stat.h, share.h, io.h, stdio.h

Category

Input/output Routines

Prototype

int _sopen(char *path, int access, int shflag[, int mode]);

int _wsopen(wchar_t *path, int access, int shflag[, int mode]);

Description

Opens a shared file.

_sopen opens the file given by path and prepares it for shared reading or writing, as determined by access, shflag, and mode.

_wsopen is the Unicode version of _sopen. The Unicode version accepts a filename that is a wchar_t character string. Otherwise, the functions perform identically.

For _sopen, access is constructed by ORing flags bitwise from the following lists:

Read/write flags

You can use only one of the following flags:

O_RDONLY	Open for reading only.
O_WRONLY	Open for writing only.
O_RDWR	Open for reading and writing.

Other access flags

You can use any logical combination of the following flags:

O_NDELAY	Not used; for UNIX compatibility.
O_APPEND	If set, the file pointer is set to the end of the file prior to each write.
O_CREA	If the file exists, this flag has no effect. If the file does not exist, the file is created, and the bits of mode are used to set the file attribute bits as in chmod.
O_TRUNC	If the file exists, its length is truncated to 0. The file attributes remain unchanged.
O_EXCL	Used only with O_CREAT. If the file already exists, an error is returned.
O_BINARY	This flag can be given to explicitly open the file in binary mode.
O_TEXT	This flag can be given to explicitly open the file in text mode.
O_NOINHERIT	The file is not passed to child programs.

Note: These O_... symbolic constants are defined in fcntl.h.

If neither O_BINARY nor O_TEXT is given, the file is opened in the translation mode set by the global variable _fmode.

If the O_CREAT flag is used in constructing access, you need to supply the mode argument to _sopen from the following symbolic constants defined in sys\stat.h.

S_IWRITE	Permission to write
S_IREAD	Permission to read
S_IREAD\|S_IWRITE	Permission to read/write

shflag specifies the type of file-sharing allowed on the file path. Symbolic constants for shflag are defined in share.h.

SH_COMPAT	Sets compatibility mode.
SH_DENYRW	Denies read/write access
SH_DENYWR	Denies write access
SH_DENYRD	Denies read access
SH_DENYNONE	Permits read/write access
SH_DENYNO	Permits read/write access

Return Value

On success, _sopen returns a nonnegative integer (the file handle), and the file pointer (that marks the current position in the file) is set to the beginning of the file.

On error, it returns -1, and the global variable errno is set to

EACCES	Permission denied
EINVACC	Invalid access code
EMFILE	Too many open files
ENOENT	Path or file function not found

Example

Copy Code

 #include <io.h>
 #include <fcntl.h>
 #include <sys\stat.h>
 #include <process.h>
 #include <share.h>
 #include <stdio.h>
 #include <stdlib.h>
 int main(void)
 {
    int handle,
        handle1;
    handle = sopen("c:\\autoexec.bat", O_RDONLY, SH_DENYWR, S_IREAD);
    if      (handle == -1)
    {
      perror (sys_errlist[errno]);
      exit (1);
    }
    if (!handle)
    {
       printf("sopen failed\n");
       exit(1);
    }
    /*      Attempt sopen for write.
    */
    handle1 = sopen("c:\\autoexec.bat", O_RDONLY, SH_DENYWR, S_IREAD);
    if      (handle1 == -1)
    {
      perror (sys_errlist[errno]);
      exit (1);
    }
    if (!handle1)
    {
       printf("sopen failed\n");
       exit(1);
    }
    close (handle);
    close (handle1);
    return 0;
}

Portability

	POSIX	Win32	ANSI C	ANSI C++
_sopen		+
_wsopen		+

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