学步园

函数名: _access
功  能: 确定文件的访问权限
用  法: int access(const char *filename, int amode);

Determine file-access permission.

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

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

参考MSDN

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

Generic-Text Routine Mappings

Example

/* ACCESS.C: This example uses _access to check the<br /> * file named "ACCESS.C" to see if it exists and if<br /> * writing is allowed.<br /> */</p> <p>#include <io.h><br /> #include <stdio.h><br /> #include <stdlib.h></p> <p>void main( void )<br /> {<br /> /* Check for existence */<br /> if( (_access( "ACCESS.C", 0 )) != -1 )<br /> {<br /> printf( "File ACCESS.C exists/n" );<br /> /* Check for write permission */<br /> if( (_access( "ACCESS.C", 2 )) != -1 )<br /> printf( "File ACCESS.C has write permission/n" );<br /> }<br /> }<br />

Output

File ACCESS.C exists
File ACCESS.C has write permission

3.在windows平台下用API函数FindFirstFile(...):

(1)检查文件是否存在:

#define _WIN32_WINNT 0x0400 </p> <p>#include <windows.h> </p> <p>int main( int argc, char * argv[])<br /> {<br /> WIN32_FIND_DATA FindFileData;<br /> HANDLE hFind;</p> <p> printf ( " Target file is %s. " , argv[ 1 ]);</p> <p> hFind = FindFirstFile(argv[ 1 ], & FindFileData);</p> <p> if (hFind == INVALID_HANDLE_VALUE) {<br /> printf ( " Invalid File Handle. Get Last Error reports %d " , GetLastError ());<br /> } else {<br /> printf ( " The first file found is %s " , FindFileData.cFileName);<br /> FindClose(hFind);<br /> }</p> <p> return ( 0 );<br /> }

(2)检查某一目录是否存在：

/// 目录是否存在的检查：<br /> bool CheckFolderExist( const string & strPath)<br /> {<br /> WIN32_FIND_DATA wfd;<br /> bool rValue = false ;<br /> HANDLE hFind = FindFirstFile(strPath.c_str(), & wfd);<br /> if ((hFind != INVALID_HANDLE_VALUE) && (wfd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))<br /> {<br /> rValue = true ;<br /> }<br /> FindClose(hFind);<br /> return rValue;<br /> }

4.使用boost的filesystem类库的exists函数

#include < boost / filesystem / operations.hpp ><br /> #include < boost / filesystem / path.hpp ><br /> #include < boost / filesystem / convenience.hpp > </p> <p>int GetFilePath(std:: string & strFilePath)<br /> {<br /> string strPath;<br /> int nRes = 0 ;</p> <p> // 指定路径<br /> strPath = " D:/myTest/Test1/Test2 " ;<br /> namespace fs = boost::filesystem;</p> <p> // 路径的可移植<br /> fs::path full_path( fs::initial_path() );<br /> full_path = fs::system_complete( fs::path(strPath, fs::native ) );<br /> // 判断各级子目录是否存在，不存在则需要创建<br /> if ( ! fs::exists( full_path ) )<br /> {<br /> // 创建多层子目录<br /> bool bRet = fs::create_directories(full_path);<br /> if ( false == bRet)<br /> {<br /> return - 1 ;<br /> }</p> <p> }<br /> strFilePath = full_path.native_directory_string();</p> <p> return 0 ;<br /> }