C/C++ 中判断某一文件或目录是否存在

 

方法一：C++中比较简单的一种办法（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;
}

方法二：利用C语言库函数（_access）

函数原型：

　　int _access( const char *path,  int mode ）

函数参数：

　　l  path：文件路径

　　l  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

方法三：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;
}

方法四：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;
}