一种判断文件存在的方法

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_access, _waccess

Determine file-access permission.

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

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

RoutineRequired HeaderOptional HeadersCompatibility_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.LIBSingle thread static library, retail versionLIBCMT.LIBMultithread static library, retail versionMSVCRT.LIBImport 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 ValueChecks File For00Existence only02Write permission04Read permission06Read 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" );

        if( (_access( "ACCESS.C", 4 )) != -1 )

            printf("File ACCESS.C has read permission\n" );

        if( (_access( "ACCESS.C", 6 )) != -1 )

            printf("File ACCESS.C has read and write permission\n" );

    }

    else

    {

        printf("File ACCESS.C does not exists\n");

    }

}