判断文件、目录是否存在：C、C++、Windows API、 boost

一、判断文件是否存在

#ifdef WIN32
#include <io.h>                      //C (Windows)    access
#else
#include <unistd.h>                  //C (Linux)      access
#endif

#include <fstream>                   //C++           fstream

#ifdef WIN32
#include <Windows.h>                 //Windows API   FindFirstFile
#include <Shlwapi.h>
#pragma comment(lib, "shlwapi.lib")  //Windows API   PathFileExists
#endif

#include <boost/filesystem.hpp>      //boost
using namespace std;

int main()
{
char file_name[] = "D://aa.txt";

//C     run in windows and linux
if ( 0 == access(file_name, 0) )  cout<<"access(): file exist."<<endl;
else                              cout<<"access(): file not exist."<<endl;

//C++     run in windows and linux
fstream fs;
fs.open(file_name, ios::in);
if (fs)   cout<<"fstream: file exist."<<endl;
else      cout<<"fstream: file not exist."<<endl;
fs.close();

//Windows API     run in windows
#ifdef WIN32
WIN32_FIND_DATA wfd;
HANDLE hFind = FindFirstFile(file_name, &wfd);
if ( INVALID_HANDLE_VALUE != hFind )   cout<<"FindFirstFile: file exist."<<endl;
else                                   cout<<"FindFirstFile: file not exist."<<endl;
CloseHandle(hFind);

if ( PathFileExists(file_name) )       cout<<"PathFileExists: file exist."<<endl;
else                                   cout<<"PathFileExists: file not exist."<<endl;

if ( INVALID_FILE_ATTRIBUTES != GetFileAttributes(file_name) )   cout<<"GetFileAttributes: file exist."<<endl;
else                                                             cout<<"GetFileAttributes: file not exist."<<endl;

if ( INVALID_HANDLE_VALUE != CreateFile(file_name, GENERIC_READ, 0, NULL, OPEN_EXISTING, NULL, NULL) )  cout<<"CreateFile: file exist."<<endl;
else                                                                                                    cout<<"CreateFile: file not exist."<<endl;
#endif

//boost      run in windows and linux
boost::filesystem::path path_file(file_name);
if ( boost::filesystem::exists(path_file) &&
boost::filesystem::is_regular_file(path_file) )   cout<<"boost: file exist."<<endl;
else                                                   cout<<"boost: file not exist."<<endl;

return 0;
}

二、判断目录是否存在

#ifdef WIN32
#include <io.h>                      //C (Windows)    access
#else
#include <unistd.h>                  //C (Linux)      access
#endif

#ifdef WIN32
#include <Windows.h>                 //Windows API   FindFirstFile
#include <Shlwapi.h>
#pragma comment(lib, "shlwapi.lib")  //Windows API   PathFileExists
#endif

#include <boost/filesystem.hpp>      //boost
using namespace std;

int main()
{
char file_name[] = "D://b";

//C     run in windows and linux
if ( 0 == access(file_name, 0) )  cout<<"access(): path exist."<<endl;
else                              cout<<"access(): path not exist."<<endl;

//Windows API     run in windows
#ifdef WIN32
WIN32_FIND_DATA wfd;
HANDLE hFind = FindFirstFile(file_name, &wfd);
if ( INVALID_HANDLE_VALUE != hFind && (wfd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) )   cout<<"FindFirstFile: path exist."<<endl;
else                                                                                        cout<<"FindFirstFile: path not exist."<<endl;
CloseHandle(hFind);

if ( PathFileExists(file_name) )       cout<<"PathFileExists: path exist."<<endl;
else                                   cout<<"PathFileExists: path not exist."<<endl;

if ( INVALID_FILE_ATTRIBUTES != GetFileAttributes(file_name) )   cout<<"GetFileAttributes: path exist."<<endl;
else                                                             cout<<"GetFileAttributes: path not exist."<<endl;
#endif

//boost      run in windows and linux
boost::filesystem::path path_file(file_name);
if ( boost::filesystem::exists(path_file) &&
boost::filesystem::is_directory(path_file) )      cout<<"boost: path exist."<<endl;
else                                                   cout<<"boost: path not exist."<<endl;

return 0;
}

三、几种方式比较

1. 精确判断文件和目录的

     FindFirstFile()            (Windows API,  Windows)

     boost                           (boost,  Windows and Linux)

2. 不精确判断文件盒目录的

      access()                     (C ,  Windows and Linux)

      PathFileExists()         (Windows API ,  Windows)

      GetFileAttributes()     (Windows API,  Windows)

3. 只能判断文件的

      fstream                       (C++ STL,  Windows and Linux)

      CreateFile()                (Windows API,  Windows)