C/C++中判断某一文件或目录是否存在

 

1.C++很简单的一种办法：

#include < iostream > #include < fstream > using namespace std; #define FILENAME "stat.dat" int main() { fstream _file; _file.open(FILENAME,ios:: in ); if ( ! _file) { cout << FILENAME << " 没有被创建 " ; } else { cout << FILENAME << " 已经存在 " ; } return 0 ; }

2.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);

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

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" ); } }

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 #include <windows.h> 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 " , FindFileData.cFileName); FindClose(hFind); } return ( 0 ); }

 

(2)检查某一目录是否存在：

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

 

4.使用boost的filesystem类库的exists函数

#include < boost / filesystem / operations.hpp > #include < boost / filesystem / path.hpp > #include < boost / filesystem / convenience.hpp > 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 ; }