Opens a file, using system call 0x3D.
| #include <dos.h> | ||
| #include <errno.h> | ||
| #include <fcntl.h> | Access mode constants | |
| #include <share.h> | Sharing mode constants |
unsigned _dos_open( char *filename, unsignedmode, int *handle );
| filename | Path to an existing file | |
| mode | Permissions | |
| handle | Pointer to integer |
The _dos_open routine uses system call 0x3D to open the existing file pointed to by filename. The handle for the opened file is copied into the integer pointed to by handle. The mode argument specifies the file's access, sharing, and inheritance modes by combining (with the OR operator) manifest constants from the three groups shown below. At most, one access mode and one sharing mode can be specified at a time.
| Constant | Mode | Meaning |
| _O_RDONLY | Access | Read-only |
| _O_WRONLY | Access | Write-only |
| _O_RDWR | Access | Both read and write |
| _SH_COMPAT | Sharing | Compatibility |
| _SH_DENYRW | Sharing | Deny reading and writing |
| _SH_DENYWR | Sharing | Deny writing |
| _SH_DENYRD | Sharing | Deny reading |
| _SH_DENYNO | Sharing | Deny neither |
| _O_NOINHERIT | Inheritance by the child process | File is not inherited |
Do not use the DOS interface I/O routines in conjunction with the console, low-level, or stream I/O routines.
If successful, the function returns 0. Otherwise, it returns the DOS error code and sets errno to one of the following manifest constants:
| Constant | Meaning |
| EACCES | Access denied (possible reasons include specifying a directory or volume ID for filename, or opening a read-only file for write access) |
| EINVAL | Sharing mode specified when file sharing not installed, or access-mode value is invalid |
| EMFILE | Too many open file handles |
| ENOENT | Path or file not found |
Standards:None
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:None
_dos_close, _dos_read, _dos_write
/* DOPEN.C: This program uses DOS I/O functions to open and close a file. */
#include <fcntl.h>
#include <stdio.h>
#include <dos.h>
void main( void )
{
int fh;
/* Open file with _dos_open function */
if( _dos_open( "data1", _O_RDONLY, &fh ) != 0 )
perror( "Open failed on input file\n" );
else
printf( "Open succeeded on input file\n" );
/* Close file with _dos_close function */
if( _dos_close( fh ) != 0 )
perror( "Close failed\n" );
else
printf( "File successfully closed\n" );
}
Open succeeded on input file
File successfully closed