_open, _dos_open

raw OCR

Opens a file for reading or writing.

Defined in header <fcntl.h>

Syntax

#include <fcntl.h>
int _open(const char *filename, int oflags);

#include <fcntl.h>
#include <share.h>
#include <dos.h>
unsigned  _dos_open(const   char *filename, unsigned oflags, int*handlep);

_open  and _dos_open    open the file specified by filename,then prepares it

Portability

DOS	UNIX	Windows	ANSI C	C++ only
■		■

Remarks

^^^ reading or writing, as determined by the value of oflags. The file is always opened in binary mode. The file handle is stored at the location pointed to by handlep.

oflags must include one of the following values:

0_RDONLY	Open for reading.

0_WRONLY	Open for writing.

ORDWR	Open for reading and writing.

On DOS 3.0 or later, the following additional values can be included in oflags (using an OR operation):

These symbolic

0_NOINHERIT	The file is not passed to child programs.

constants are defined in fcntl.t)

SH_COMPAT	Allow other opens with SH_COMPAT.	The call will fail

and stiare.ti.

if the file has already been opened in any other shared mode.

SH_DENYRW	Only the current handle may have access to the file.

SH_DENYWR	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.

Only one of the SHDENYxx	values can be included in a single

_dos_open or _open under DOS 3.0 or later. 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 successful completion, _open returns a nonnegative integer (the file handle). On successful completion, _dos_open returns 0, and stores the file handle at the location pointed to by handlep. The file pointer, which marks the current position in the file, is set to the beginning of the file.

On error, _open returns -1 and _dos_open returns the DOS error code. For both functions, the global variable errno is set to one of the following:

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

Example

#include <string.h>
iinclude <stdio.h>
#include <fcntl.h> •
#include <io.h>

int main(void) /* Example  for _open. */
{
   int handle;
   char msg[] =  "Hello world\n";
   if ((handle = _open("TEST.$$$",  0_RDWR)      -1) {
      perrorC Error: ") ;
      return 1;
   _v;rite(handle, msg, strlen(msg)
   _close (handle);
   return 0;

[include <string.h>
[include <stdio.h>
#include <fcntl.h>
(include <dos.h>

int main (void)  /* Example for _dos_open. */
{
   int handle;
   unsigned nbytes;
   char msg[] =  "Hello world\n";
   if (_dos_open("TEST.$$$",  0_RDWR, &handle) != 0)  {
      perror("Unable  to open TEST.$$$"),•
      return 1;

   if  (_dos_write(handle, msg, strlen(msg),&nbytes)
      perror( "Unable to write to TEST.$$$"),•
   printf("%u bytes written  to TEST.$$$\n",nbytes) ;
   _dos_close (handle);
   return 0;

Differences from modern implementations

Nothing recorded yet.

Modern references

Microsoft C runtime (search)

These are search links, not yet checked by hand.

Extraction notes

heading `_open, _Glos_open` read as `_open, _dos_open`

Stable link: /3.1/fcntl.h/_open/ · short form /3.1/_open/