`_getdiskfree`

Article
12/02/2022

Get information about a disk drive such as total clusters, available clusters, sectors per cluster, and bytes per sector.

Important

This API cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.

Syntax

unsigned _getdiskfree(
   unsigned drive,
   struct _diskfree_t * driveinfo
);

Parameters

drive
The disk drive for which you want information.

driveinfo
A _diskfree_t structure that will be populated with information about the drive.

Return value

If the function succeeds, the return value is zero. If the function fails, the return value is the error code. The value errno is set for any errors that are returned by the operating system. For more information about error conditions that are indicated by errno, see errno constants.

Remarks

The _diskfree_t structure is defined in Direct.h.

struct _diskfree_t {
   unsigned total_clusters;      // The total number of clusters, both used and available, on the disk.
   unsigned avail_clusters;      // The number of unused clusters on the disk.
   unsigned sectors_per_cluster; // The number of sectors in each cluster.
   unsigned bytes_per_sector;    // The size of each sector in bytes.
};

This function validates its parameters. If the driveinfo pointer is NULL or drive specifies an invalid drive, this function invokes an invalid parameter handler, as described in Parameter validation. If execution is allowed to continue, the function returns EINVAL and sets errno to EINVAL. Valid drives range from 0 to 26. A drive value of 0 specifies the current drive; thereafter, numbers map to letters of the English alphabet such that 1 indicates drive A, 3 indicates drive C, and so on.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
`_getdiskfree`	`<direct.h>`

For more compatibility information, see Compatibility.

Example

// crt_getdiskfree.c
// compile with: /c
#include <windows.h>
#include <direct.h>
#include <stdio.h>

int main(int argc, char* argv[]) 
{
    ULONG uDriveMask = _getdrives();

    for (unsigned uDrive = 1; uDrive <= 26; ++uDrive) 
    {
        if (uDriveMask & 1)
        {
            struct _diskfree_t df = { 0 };
            unsigned uErr = _getdiskfree(uDrive, &df);
            printf("\nDrive: %c\n", uDrive + 'A' - 1);
            
            if (uErr == 0)
            {
                printf("\tTotal clusters:      %11u\n", df.total_clusters);
                printf("\tAvailable clusters:  %11u\n", df.avail_clusters);
                printf("\tSectors per cluster: %11u\n", df.sectors_per_cluster);
                printf("\tBytes per sector:    %11u\n", df.bytes_per_sector);
            }
            else
            {
                WCHAR errMsg[80];
                unsigned uLen = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL,
                    uErr, 0, errMsg, sizeof(errMsg), NULL);
                printf("%S\n", errMsg);
            }
        }
        uDriveMask >>= 1;
    }
}

Drive: C
        Total clusters:        249754111
        Available clusters:    160184686
        Sectors per cluster:           8
        Bytes per sector:            512