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

File ACCESS.C existsFile ACCESS.C has write permission