vc6 c++ se file esiste

[okay]

fate un esempio su questa apertura:

per sapere se il file settings.cfg esiste in directory

io apro così in lettura
ifstream File("settings.cfg");
File >> m_dwCreationWidth0;
File >> m_dwCreationHeight0;
File >> wf;
File.close();
........tutto okay, ma se cancello il file settings.cfg dalla directory come posso controllare l'errore che il file non esiste (conosco altri costrutti, ma non nè ho trovati per questo sopra)
tipo:
if (( fpt = fopen ( "sample.dat", "r" )) == NULL)
printf ("\nERROR- Cannot open the designated file\n");




ciao

[pela]

prova a fare
if(!File)
// errore in apertura

[ri]

_access, _waccess
Determine file-access permission.

int _access( const char *path, int mode );

int _waccess( const wchar_t *path, int mode );

Routine Required Header Optional Headers Compatibility
_access <io.h> <errno.h> Win 95, Win NT
_waccess <wchar.h> or <io.h> <errno.h> Win NT


For additional compatibility information, see Compatibility in the Introduction.

Libraries

LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version


Return Value

Each of these functions returns 0 if the file has the given mode. The function returns –1 if the named file does not exist or is not accessible in the given mode; in this case, errno is set as follows:

EACCES

Access denied: file’s permission setting does not allow specified access.

ENOENT

Filename or path not found.

Parameters

path

File or directory path

mode

Permission setting

Remarks

When used with files, the _access function determines whether the specified file exists and can be accessed as specified by the value of mode. When used with directories, _access determines only whether the specified directory exists; in Windows NT, all directories have read and write access.

mode Value Checks File For
00 Existence only
02 Write permission
04 Read permission
06 Read and write permission


_waccess is a wide-character version of _access; the path argument to _waccess is a wide-character string. _waccess and _access behave identically otherwise.

Generic-Text Routine Mappings

TCHAR.H Routine _UNICODE & _MBCS Not Defined _MBCS Defined _UNICODE Defined
_taccess _access _access _waccess


Example

/* ACCESS.C: This example uses _access to check the
* file named "ACCESS.C" to see if it exists and if
* writing is allowed.
*/

#include <io.h>
#include <stdio.h>
#include <stdlib.h>

void main( void )
{
/* Check for existence */
if( (_access( "ACCESS.C", 0 )) != -1 )
{
printf( "File ACCESS.C exists\n" );
/* Check for write permission */
if( (_access( "ACCESS.C", 2 )) != -1 )
printf( "File ACCESS.C has write permission\n" );
}
}


Output

File ACCESS.C exists
File ACCESS.C has write permission