C++中判断某一文件或目录是否存在

方法1. C++中较简单方法（使用文件流打开文件）

#include <iostream>

#include <fstream>

using namespace std;

#define FILENAME "*.dat" // 指定文件名

int main( void )

{

fstream _file;

_file.open(FILENAME, ios::in);

if(!_file)

{

cout<<FILENAME<<"没有被创建!"<<endl;

}

else

{

cout<<FILENAME<<"已经存在!"<<endl;

}

cin.get();

return 0;

}

方法2. 利用C语言库函数（_access）

函数原型：

int _access( const char *path, int mode ）

函数参数：

path：文件路径。

mode：读写属性。

返回值（MSDN）：

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.

EINVAL Invalid parameter.

函数功能（MSDN）：

When used with files, the _access function determines whether the specified file exists and can be accessed as specified by the value of mode（见下图表）. When used with directories, _access determines only whether the specified directory exists; in Windows NT, all directories have read and write access.

/* 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 " );

}

输出：

>>File ACCESS.C exists.

>>File ACCESS.C has write permission

方法3. 使用Windows API函数FindFirstFile(...)

(1) 检查某一文件是否存在：

#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 FindFileData;

BOOL bValue = false;

HANDLE hFind = FindFirstFile(strPath.c_str(), &FindFileData);

if ((hFind != INVALID_HANDLE_VALUE) && (wfd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))

{

bValue = TRUE;

}

FindClose(hFind);

return bValue;

}

方法4. 使用boost库中filesystem类库的exists函数

#include <boost/filesystem/operations.hpp>

#include <boost/filesystem/path.hpp>

#include <boost/filesystem/convenience.hpp>

using namespace boost::filesystem;

int GetFilePath(std::string &strFilePath)

{

string strPath;

int nRes = 0;

//指定路径

strPath = "C:\";

path full_path( initial_path() );

full_path = system_complete( path(strPath, native ) );

//判断各级子目录是否存在，不存在则需要创建

if ( !exists( full_path ) )

{

bool bRet = create_directories(full_path);

if (false == bRet)

{

return -1;

}

strFilePath = full_path.native_directory_string();

return 0;

}