How To Use the GetDiskFreeSpaceEx() API to Obtain Disk Free Space Amounts

The Win32 API function GetDiskFreeSpace reports the amount of total and free disk space available on a computer. However, for disks that are larger than 2 gigabytes, the GetDiskFreeSpace function may return misleading values. The new GetDiskFreeSpaceEx Win32 API function returns correct values for all disks, including those that are larger than 2 GB. GetDiskFreeSpaceEx returns values for the total amount of space, the total amount of free space, and the total amount of free space available to the user associated with the calling thread.

This article provides sample code that uses this new function to obtain disk space information for any disk.

GetDiskFreeSpaceEx is supported on Windows NT 4.0 or later and Windows 95 OSR2 or later. It is not supported on Windows CE. Your code can determine whether the GetDiskFreeSpaceEx function is available by checking to see if it is exported by Kernel32. For additional information, see the "Remarks" section for GetDiskFreeSpaceEx in the MSDN Library.

Example of How to Get Disk Space Information by Using GetDiskFreeSpaceEx

1. Create a Standard EXE project in Microsoft Visual Basic. Form1 is created by default.
2. Add a TextBox control to Form1.
3. Paste the following code into the Form1 module:

   Private Declare Function GetDiskFreeSpaceEx Lib "kernel32" _
       Alias "GetDiskFreeSpaceExA" (ByVal lpDirectoryName As String, _
       lpFreeBytesAvailableToCaller As Currency, _
       lpTotalNumberOfBytes As Currency, _
       lpTotalNumberOfFreeBytes As Currency) As Long
   
   Private Sub Form_Click()
       Dim Status As Long
       Dim TotalBytes As Currency
       Dim FreeBytes As Currency
       Dim BytesAvailableToCaller As Currency
       
       Status = GetDiskFreeSpaceEx(Text1.Text, BytesAvailableToCaller, _
         TotalBytes, FreeBytes)
       If Status <> 0 Then
           MsgBox Format(TotalBytes * 10000, "#,##0"), , "Total Bytes"
           MsgBox Format(FreeBytes * 10000, "#,##0"), , "Free Bytes"
           MsgBox Format(BytesAvailableToCaller * 10000, "#,##0"), , _
             "Bytes Available To Caller"
       End If
   End Sub
   					

4. Press F5 to run the program.
5. Type C: in the text box, and then click the form. The message boxes will display values for the total space, free space, and free space available to the user associated with the calling thread.NOTE: If you enter a directory on the disk of interest in the text box as a Universal Naming Convention (UNC) name, you must terminate it with a backslash. For example, "\\MyServer\MyShare" must be specified as "\\MyServer\MyShare\". You can specify any directory on the disk. If you do not specify a directory, GetDiskFreeSpaceEx returns information about the disk that contains the current directory.

MSDN Library; Platform SDK; Base Services; Files and I/O; File I/O; File I/O Reference; File I/O Functions; GetDiskFreeSpace

MSDN Library; Platform SDK; Base Services; Files and I/O; File I/O; File I/O Reference; File I/O Functions; GetDiskFreeSpaceEx


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