_rtl_open, _wrtl

Header File

io.h

Category

Input/output Routines

Prototype

int _rtl_open(const char *filename, int oflags);

int _wrtl_open(const wchar_t *path, int oflags);

Description

Opens a file for reading or writing.

Note: The _rtl_open function replaces _open which is obsolete.

_rtl_open opens the file specified by filename, then prepares it for reading or writing, as determined by the value of oflags. The file is always opened in binary mode.

oflags uses the flags from the following two lists. Only one flag from List 1 can be used (and one must be used) and the flags in List 2 can be used in any logical combination.

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

The following additional values can be included in oflags (using an OR operation):

O_NOINHERIT	The file is not passed to child programs.
SH_COMPAT	Allow other opens with SH_COMPAT. All other openings of a file with the SH_COMPAT flag must be opened using SH_COMPAT flag. You can request a file open that uses SH_COMPAT logically OR’ed with some other flag (for example, SH_COMPAT \| SH_DENWR is allowed). The call will fail if the file has already been opened in any other shared mode.
SH_DENYRW	Only the current handle can have access to the file.
SH_DENWR	Allow only reads from any other open to the file.
SH_DENYRD	Allow only writes from any other open to the file.
SH_DENYNO	Allow other shared opens to the file, but not other SH_COMPAT opens.

Note: These symbolic constants are defined in fcntl.h and share.h.

Only one of the SH_DENYxx values can be included in a single _rtl_open routine. These file-sharing attributes are in addition to any locking performed on the files.

The maximum number of simultaneously open files is defined by HANDLE_MAX.

Return Value

On success:_rtl_open returns a non-negative integer (the file handle). The file pointer, which marks the current position in the file, is set to the beginning of the file.

On error, it returns -1 and sets the global variable errno to one of the following values:

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

Example

Copy Code

#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
   int handle;
   char msg[] = "Hello world";
   if ((handle = _rtl_open("TEST.$$$", O_RDWR)) == -1)
   {
      perror("Error:");
      return 1;
   }
   _rtl_write(handle, msg, strlen(msg));
   _rtl_close(handle);
   return 0;
}

Portability

	POSIX	Win32	ANSI C	ANSI C++
_rtl_open		+
_wrtl_open		NT only

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