C/C++中使用库函数判断某一文件或目录是否存在

转自http://blog.csdn.net/roger_77/article/details/1538447

利用 c 语言的库的办法：

函数名: access 

功  能: 确定文件的访问权限 

用  法: int access(const char *filename, int amode); 

以前一直没用过这个函数,今天调试程序发现了这个函数,感觉挺好用,尤其是判断一个文件或文件夹是否存在的时候,用不着再find了,文件的话还可以检测读写权限,文件夹的话则只能判断是否存在,下面摘自MSDN：

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

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

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 " );
      /* Check for write permission */
      if( (_access( "ACCESS.C", 2 )) != -1 )
         printf( "File ACCESS.C has write permission " );
   }
}

Output[/code]

File ACCESS.C existsFile ACCESS.C has write permission