C/C++中如何判斷某一文件或目錄是否存在

以下文章是對C/C++中判斷某一文件或目錄是否存在的實現代碼進行了詳細的分析介紹，需要的朋友可以參考下  

1.C++很簡單的一種辦法：

復制代碼 代碼如下:
#include <iostream>
#include <fstream>
using namespace std;
#define FILENAME "stat.dat"
int main()
{
     fstream _file;
     _file.open(FILENAME,ios::in);
     if(!_file)
     {
         cout<<FILENAME<<"沒有被創建";
      }
      else
      {
          cout<<FILENAME<<"已經存在";
      }
      return 0;
}

2.利用 c 語言的庫的辦法：
函數名: access
功  能: 確定文件的訪問權限
用  法: int access(const char *filename, int amode);
以前一直沒用過這個函數,今天調試程序發現了這個函數,感覺挺好用,尤其是判斷一個文件或文件夾是否存在的時候,用不著再find了,文件的話還可以檢測讀寫權限,文件夾的話則只能判斷是否存在,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

復制代碼 代碼如下:
/* 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 " );
   }
}

OutputFile ACCESS.C existsFile ACCESS.C has write permission
3.在windows平台下用API函數FindFirstFile(...):
(1)檢查文件是否存在:

復制代碼 代碼如下:
#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)檢查某一目錄是否存在：

復制代碼 代碼如下:
///目錄是否存在的檢查：
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類庫的exists函數

復制代碼 代碼如下:

#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;
    //指定路徑           
    strPath = "D:/myTest/Test1/Test2";
    namespace fs = boost::filesystem;
    //路徑的可移植
    fs::path full_path( fs::initial_path() );
    full_path = fs::system_complete( fs::path(strPath, fs::native ) );
    //判斷各級子目錄是否存在，不存在則需要創建
    if ( !fs::exists( full_path ) )
    {
        // 創建多層子目錄
        bool bRet = fs::create_directories(full_path);
        if (false == bRet)
        {
            return -1;
        }
    }
    strFilePath = full_path.native_directory_string();
    return 0;
}