Get a list of the available drives and their sizes

I know you can use a combination of GetLogicalDrives() and GetDiskFreeSpaceEx() to get the list of drives and their sizes. I've been using Ge开发者_运维问答tDiskFreeSpaceEx() with no problem but when I try to use GetLogicalDrives() I ran into a problem: I don't want to have to check each possible letter to see whether it exists or not before passing it to GetDiskFreeSpaceEx().

Is there a simpler way to get the list of drives (disk) on the system and what their sizes are? I am using C, on Windows.

I want to make something clear, I KNOW it might be easier using C# and WMI, I have no interest on that so please do not post that as a possible solution. If you want to point to how is done in C and WMI, go for it. NO C++ or C# thanks! (like someone did in my previous question)

You can use GetLogicalDriveStrings - this returns a buffer containing all valid drive letters on the system.

UPDATE:

Here is sample program I wrote that enumerates the drives using GetLogicalDriveStrings and outputs some basic information about them.

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

int __cdecl main()
{
    DWORD cchBuffer;
    WCHAR* driveStrings;
    UINT driveType;
    PWSTR driveTypeString;
    ULARGE_INTEGER freeSpace;

    // Find out how big a buffer we need
    cchBuffer = GetLogicalDriveStrings(0, NULL);

    driveStrings = (WCHAR*)malloc((cchBuffer + 1) * sizeof(TCHAR));
    if (driveStrings == NULL)
    {
        return -1;
    }

    // Fetch all drive strings    
    GetLogicalDriveStrings(cchBuffer, driveStrings);

    // Loop until we find the final '\0'
    // driveStrings is a double null terminated list of null terminated strings)
    while (*driveStrings)
    {
        // Dump drive information
        driveType = GetDriveType(driveStrings);
        GetDiskFreeSpaceEx(driveStrings, &freeSpace, NULL, NULL);

        switch (driveType)
        {
        case DRIVE_FIXED:
            driveTypeString = L"Hard disk";
            break;

        case DRIVE_CDROM:
            driveTypeString = L"CD/DVD";
            break;

        case DRIVE_REMOVABLE:
            driveTypeString = L"Removable";
            break;

        case DRIVE_REMOTE:
            driveTypeString = L"Network";
            break;

        default:
            driveTypeString = L"Unknown";
            break;
        }

        printf("%S - %S - %I64u GB free\n", driveStrings, driveTypeString,
                  freeSpace.QuadPart / 1024 / 1024 / 1024);

        // Move to next drive string
        // +1 is to move past the null at the end of the string.
        driveStrings += lstrlen(driveStrings) + 1;
    }

    free(driveStrings);

    return 0;

}

On my machine this outputs:

C:\ - Hard disk - 181 GB free
D:\ - CD/DVD - 0 GB free
E:\ - Hard disk - 806 GB free

GetLogicalDrives() is the system-provided API for that. A simple for() loop will translate its result into drive letters, like this:

DWORD d = GetLogicalDrives();
int i;
TCHAR Drive[] = _T("A:\\");
for(i=0;i<26;i++)
{
    if(d & (1<<i))
    {
        Drive[0] = _T('A')+i;
        GetDiskFreeSpaceEx(Drive, .....);
    }
}

And if you're not satisfied with the level of service that Stack Overflow provides, feel free to ask for your money back.

This is Michael's code that was rejected as an edit. It seg faults on the free () unless a dummy variable 'singleDriveString' is inserted thus:

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

int __cdecl main()
{
DWORD cchBuffer;
WCHAR* driveStrings;
UINT driveType;
PWSTR driveTypeString;
ULARGE_INTEGER freeSpace;

// Find out how big a buffer we need
cchBuffer = GetLogicalDriveStrings(0, NULL);

driveStrings = (WCHAR*)malloc((cchBuffer + 1) * sizeof(TCHAR));
if (driveStrings == NULL)
{
    return -1;
}

// Fetch all drive strings    
GetLogicalDriveStrings(cchBuffer, driveStrings);

// Loop until we find the final '\0'
// driveStrings is a double null terminated list of null terminated strings)
wchar_t * singleDriveString = driveStrings;
while (*singleDriveString)
{
    // Dump drive information
    driveType = GetDriveType(singleDriveString);
    GetDiskFreeSpaceEx(singleDriveString, &freeSpace, NULL, NULL);

    switch (driveType)
    {
    case DRIVE_FIXED:
        driveTypeString = L"Hard disk";
        break;

    case DRIVE_CDROM:
        driveTypeString = L"CD/DVD";
        break;

    case DRIVE_REMOVABLE:
        driveTypeString = L"Removable";
        break;

    case DRIVE_REMOTE:
        driveTypeString = L"Network";
        break;

    default:
        driveTypeString = L"Unknown";
        break;
    }

    printf("%S - %S - %I64u GB free\n", singleDriveString, driveTypeString,
              freeSpace.QuadPart / 1024 / 1024 / 1024);

    // Move to next drive string
    // +1 is to move past the null at the end of the string.
    singleDriveString += lstrlen(singleDriveString) + 1;
}

free(driveStrings);

return 0;

}