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
/*
: This example uses _access to check the
* file named "" to see if it exists and if
* writing is allowed.
*/
#include
<
>
#include
<
>
#include
<
>
void
main(
void
)
{
/*
Check for existence
*/
if
( (_access(
"
"
,
0
))
!=
-
1
)
{
printf(
"
File exists
"
);
/*
Check for write permission
*/
if
( (_access(
"
"
,
2
))
!=
-
1
)
printf(
"
File has write permission
"
);
}
}
File existsFile has write permission
3.在windows平台下用API函数FindFirstFile(...):
(1)检查文件是否存在:
#include " "
int
main( int argc, char * argv[])
{
WIN32_FIND_DATA FindFileData;
HANDLE hFind;
printf ( " Target file is %s. " , argv[ 1 ]);
hFind = FindFirstFile(argv[ 1 ], & FindFileData);
if (hFind == INVALID_HANDLE_VALUE) {
printf ( " Invalid File Handle. Get Last Error reports %d " , GetLastError ());
} else {
printf ( " The first file found is %s " , );
FindClose(hFind);
}
return ( 0 );
}
(2)检查某一目录是否存在：
bool CheckFolderExist( const string & strPath)
{
WIN32_FIND_DATA wfd;
bool rValue = false ;
HANDLE hFind = FindFirstFile(strPath.c_str(), & wfd);
if ((hFind != INVALID_HANDLE_VALUE) && ( & FILE_ATTRIBUTE_DIRECTORY))
{
rValue = true ;
}
FindClose(hFind);
return rValue;
}
4.使用boost的filesystem类库的exists函数
#include < boost / filesystem / >
#include < boost / filesystem / >
int GetFilePath(std:: string & strFilePath)
{
string strPath;
int nRes = 0 ;
// 指定路径
strPath = " D:/myTest/Test1/Test2 " ;
namespace fs = boost::filesystem;
// 路径的可移植
fs::path full_path( fs::initial_path() );
full_path = fs::system_complete( fs::path(strPath, fs::native ) );
// 判断各级子目录是否存在，不存在则需要创建
if ( ! fs::exists( full_path ) )
{
// 创建多层子目录
bool bRet = fs::create_directories(full_path);
if ( false == bRet)
{
return - 1 ;
}
}
strFilePath = full_path.native_directory_string();
return 0 ;
}