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_access, _waccess

Visual Studio .NET 2003

Determine file-access permission.

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

Parameters

path: File or directory path.
mode: Permission setting.

Return Value

Each function 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.

See _doserrno, errno, _sys_errlist, and _sys_nerr for more information on these, and other, return codes.

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 and Windows 2000, 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

Requirements

Routine	Required header	Optional headers	Compatibility
_access	<io.h>	<errno.h>	Win 98, Win Me, Win NT, Win 2000, Win XP
_waccess	<wchar.h> or <io.h>	<errno.h>	Win NT, Win 2000, Win XP

For additional compatibility information, see Compatibility in the Introduction.

Libraries

All versions of the C run-time libraries.

Example

This example uses _access to check the file named crt_ACCESS.C to see if it exists and if writing is allowed.

// crt_access.c
#include  <io.h>
#include  <stdio.h>
#include  <stdlib.h>

int main( void )
{
   /* Check for existence */
   if( (_access( "crt_ACCESS.C", 0 )) != -1 )
   {
      printf( "File crt_ACCESS.C exists\n" );
      /* Check for write permission */
      /* assume file is read-only */
      if( (_access( "crt_ACCESS.C", 2 )) == -1 )
         printf( "File crt_ACCESS.C does not have write permission\n" );
   }
}

Output

File crt_ACCESS.C exists
File crt_ACCESS.C does not have write permission