How to get the list of all drives in C

Question

Is there any method using which i can list down all the available drives and their folder content. ie i want to access all the drives and then the folders in each drive and then the sub-folders of each folder and so on till the last possible level in each drive.

C language .. Windows platform .. i have tried using alphabetic array with system() but am unable to get the names of files and folders .

Answer 1

This is not "standard C" (ie: ANSI, C89, C99, etc), but it makes minimal use of operating-system specific calls (ie: just "windows.h", not MS .NET or MFC technologies). This is the minimalist approach to what you are attempting to do. Once you have a list of all drive letters, you need to query each drive recursively for its directory listings.

This is a mix of C and C++, but you'll likely be using a free version of Visual Studio to build this anyways.

Code Listing - Get drive letters

---

#include <windows.h>
#include <stdio.h>


int main()
{
    char buf[255];
    // get the drive letters as a set of strings
    int sz = GetLogicalDriveStrings(sizeof(buf), buf);
    if( sz > 0)
    {
        // buf now contains a list of all the drive letters.  Each drive letter is
        // terminated with '\0' and the last one is terminated by two consecutive '\0' bytes.
        char* p1 = buf;
        char* p2;
        while( *p1 != '\0' && (p2 = strchr(p1,'\0')) != NULL )
        {
            printf("%s\n", p1);
            p1 = p2+1;
        }
    }
    else
    {
        // Oops! something went wrong so display the error message
        DWORD dwError = GetLastError();
        FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, 0, dwError, 0, buf, sizeof(buf), 0);
        printf("%s\n", buf);

    }
}

Code Listing - Directory listing

---

#include <windows.h>
#include <tchar.h> 
#include <stdio.h>
#include <strsafe.h>
#pragma comment(lib, "User32.lib")

void DisplayErrorBox(LPTSTR lpszFunction);

int _tmain(int argc, TCHAR *argv[])
{
   WIN32_FIND_DATA ffd;
   LARGE_INTEGER filesize;
   TCHAR szDir[MAX_PATH];
   size_t length_of_arg;
   HANDLE hFind = INVALID_HANDLE_VALUE;
   DWORD dwError=0;

   // If the directory is not specified as a command-line argument,
   // print usage.

   if(argc != 2)
   {
      _tprintf(TEXT("\nUsage: %s <directory name>\n"), argv[0]);
      return (-1);
   }

   // Check that the input path plus 3 is not longer than MAX_PATH.
   // Three characters are for the "\*" plus NULL appended below.

   StringCchLength(argv[1], MAX_PATH, &length_of_arg);

   if (length_of_arg > (MAX_PATH - 3))
   {
      _tprintf(TEXT("\nDirectory path is too long.\n"));
      return (-1);
   }

   _tprintf(TEXT("\nTarget directory is %s\n\n"), argv[1]);

   // Prepare string for use with FindFile functions.  First, copy the
   // string to a buffer, then append '\*' to the directory name.

   StringCchCopy(szDir, MAX_PATH, argv[1]);
   StringCchCat(szDir, MAX_PATH, TEXT("\\*"));

   // Find the first file in the directory.

   hFind = FindFirstFile(szDir, &ffd);

   if (INVALID_HANDLE_VALUE == hFind) 
   {
      DisplayErrorBox(TEXT("FindFirstFile"));
      return dwError;
   } 

   // List all the files in the directory with some info about them.

   do
   {
      if (ffd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
      {
         _tprintf(TEXT("  %s   <DIR>\n"), ffd.cFileName);
      }
      else
      {
         filesize.LowPart = ffd.nFileSizeLow;
         filesize.HighPart = ffd.nFileSizeHigh;
         _tprintf(TEXT("  %s   %ld bytes\n"), ffd.cFileName, filesize.QuadPart);
      }
   }
   while (FindNextFile(hFind, &ffd) != 0);

   dwError = GetLastError();
   if (dwError != ERROR_NO_MORE_FILES) 
   {
      DisplayErrorBox(TEXT("FindFirstFile"));
   }

   FindClose(hFind);
   return dwError;
}


void DisplayErrorBox(LPTSTR lpszFunction) 
{ 
    // Retrieve the system error message for the last-error code

    LPVOID lpMsgBuf;
    LPVOID lpDisplayBuf;
    DWORD dw = GetLastError(); 

    FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | 
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        dw,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPTSTR) &lpMsgBuf,
        0, NULL );

    // Display the error message and clean up

    lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT, 
        (lstrlen((LPCTSTR)lpMsgBuf)+lstrlen((LPCTSTR)lpszFunction)+40)*sizeof(TCHAR)); 
    StringCchPrintf((LPTSTR)lpDisplayBuf, 
        LocalSize(lpDisplayBuf) / sizeof(TCHAR),
        TEXT("%s failed with error %d: %s"), 
        lpszFunction, dw, lpMsgBuf); 
    MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK); 

    LocalFree(lpMsgBuf);
    LocalFree(lpDisplayBuf);
}

References

---

1. List Windows Logical Drive Letters , Accessed 2014-08-01, <http://www.daniweb.com/software-development/c/code/237803/list-windows-logical-drive-letters>
2. Listing the Files in a Directory , Accessed 2014-08-01, <http://msdn.microsoft.com/en-us/library/windows/desktop/aa365200%28v=vs.85%29.aspx>

Answer 2

Standard C has no way to directly address the drive, or, for that matter, even know what a drive is.

Generally, each C compiler vendor will include a library which handles those things for the specific platform the compiler is written for. But these are all specific to the vendor.

Boost has cross-platform library for C++, including one for dealing with the file system.