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_access, _waccess

 

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Determines if a file is read-only or not. More secure versions are available; see _access_s, _waccess_s.

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

Parameters

path
File or directory path.

mode
Read/write attribute.

Each function returns 0 if the file has the given mode. The function returns –1 if the named file does not exist or does not have the given mode; in this case, errno is set as shown in the following table.

EACCES
Access denied: the file's permission setting does not allow specified access.

ENOENT
File name or path not found.

EINVAL
Invalid parameter.

For more information about these and other return codes, see _doserrno, errno, _sys_errlist, and _sys_nerr.

When used with files, the _access function determines whether the specified file or directory exists and has the attributes specified by the value of mode. When used with directories, _access determines only whether the specified directory exists; in Windows 2000 and later operating systems, all directories have read and write access.

mode valueChecks file for
00Existence only
02Write-only
04Read-only
06Read and write

This function only checks whether the file and directory are read-only or not, it does not check the filesystem security settings. For that you need an access token. For more information on filesystem security, see Access Tokens. An ATL class exists to provide this functionality; see CAccessToken Class.

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

This function validates its parameters. If path is NULL or mode does not specify a valid mode, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, the function sets errno to EINVAL and returns -1.

Generic-Text Routine Mappings

Tchar.h routine_UNICODE and _MBCS not defined_MBCS defined_UNICODE defined
_taccess_access_access_waccess
RoutineRequired headerOptional headers
_access<io.h><errno.h>
_waccess<wchar.h> or <io.h><errno.h>

The following example uses _access to check the file named crt_ACCESS.C to see whether it exists and whether writing is allowed.

// crt_access.c  
// compile with: /W1  
// This example uses _access to check the file named  
// crt_ACCESS.C to see if it exists and if writing is allowed.  
  
#include  <io.h>  
#include  <stdio.h>  
#include  <stdlib.h>  
  
int main( void )  
{  
    // Check for existence.  
    if( (_access( "crt_ACCESS.C", 0 )) != -1 )  
    {  
        printf_s( "File crt_ACCESS.C exists.\n" );  
  
        // Check for write permission.  
        // Assume file is read-only.  
        if( (_access( "crt_ACCESS.C", 2 )) == -1 )  
            printf_s( "File crt_ACCESS.C does not have write permission.\n" );  
    }  
}  

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

System.IO.FileAccess

File Handling
_chmod, _wchmod
_fstat, _fstat32, _fstat64, _fstati64, _fstat32i64, _fstat64i32
_open, _wopen
_stat, _wstat Functions

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