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