C++檢測文件或者目錄是否存在

1.C++：

#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,用不着再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：

/* 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 " );
   }
}

Output

File ACCESS.C existsFile ACCESS.C has write permission

3.在windows平臺下用API函數FindFirstFile(...):

#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：

///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：

#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;
}