C/C++中判断某一文件或目录是否存在

1. C++很简单的一种办法，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<<"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，如下：

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"intmain(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;}