C/C++中判断某一文件或目录是否存在-阿里云开发者社区

C/C++中判断某一文件或目录是否存在

2017-12-18 4751

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简介：

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);
以前一直没用过这个函数,今天调试程序发现了这个函数,感觉挺好用,尤其是判断一个文件或文件夹是否存在的时候,用不着再find了,文件的话还可以检测读写权限,文件夹的话则只能判断是否存在,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 ;
}

本文转自博客园知识天地的博客，原文链接：C/C++中判断某一文件或目录是否存在，如需转载请自行联系原博主。

C/C++中判断某一文件或目录是否存在

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