DOCUMENT:Q291573 31-MAR-2001 [vbwin] TITLE :HOWTO: Use Visual Basic to List Active Logical Drives PRODUCT :Microsoft Visual Basic for Windows PROD/VER::5.0,6.0 OPER/SYS: KEYWORDS:kbsample kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 - Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 ------------------------------------------------------------------------------- SUMMARY ======= You can determine which drive letters are in use on a local computer by using the GetLogicalDriveStrings Win32 API. This list of drive letters will be the drive letters of all active drives on the local computer, including floppy drives, hard disks, mapped drives, and other drives that are mapped to a drive letter. MORE INFORMATION ================ The GetLogicalDriveStrings API function returns a string containing a list of all active drive letters on the local computer. The format of the string is a null-separated list of drive letters with a terminating null at the end of the string. For example, a computer with a single floppy drive (A:) and a single hard disk drive (C:) would have a string of the following format returned by GetLogicalDriveStrings: A:\C:\ This string can be parsed to list the active drives. The following Visual Basic code sample demonstrates how to retrieve and parse a list of drives. Note that this can also be used to create a control or feature similar to the DriveListBox. Step-by-Step Example -------------------- 1. Start a new Visual Basic Standard EXE project. Form1 is created by default. 2. Add a new command button (Command1) and a listbox (List1) to Form1. 3. Add the following code to Form1's code window: Option Explicit Private Declare Function GetLogicalDriveStrings Lib "kernel32" _ Alias "GetLogicalDriveStringsA" _ (ByVal nBufferLength As Long, ByVal lpBuffer As String) As Long Private Function GetDriveStrings() As String ' Wrapper for calling the GetLogicalDriveStrings API Dim result As Long ' Result of our api calls Dim strDrives As String ' String to pass to api call Dim lenStrDrives As Long ' Length of the above string ' Call GetLogicalDriveStrings with a buffer size of zero to ' find out how large our stringbuffer needs to be result = GetLogicalDriveStrings(0, strDrives) strDrives = String(result, 0) lenStrDrives = result ' Call again with our new buffer result = GetLogicalDriveStrings(lenStrDrives, strDrives) If result = 0 Then ' There was some error calling the API ' Pass back an empty string ' NOTE - TODO: Implement proper error handling here GetDriveStrings = "" Else GetDriveStrings = strDrives End If End Function Private Sub Command1_Click() Dim strDrives As String ' Find out what drives we have on this machine strDrives = GetDriveStrings() If strDrives = "" Then ' No drives were found MsgBox "No Drives were found!", vbCritical Else ' Walk through the string and list each drive DisplayDriveTypes strDrives End If End Sub Private Sub DisplayDriveTypes(drives As String) ' Walk through the logical drive string and display the drive ' letters. The logical drive string is a null seperated ' double null terminated string. Dim pos As Long Dim drive As String List1.Clear pos = 1 Do While Not Mid$(drives, pos, 1) = Chr(0) drive = Mid$(drives, pos, 3) pos = pos + 4 List1.AddItem UCase(drive) Loop End Sub 4. Click Run or press the F5 key to run the project. Result: The drive letter of each logical drive on the system is displayed in the listbox. REFERENCES ========== For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base: Q190000 HOWTO: Get Started Programming with the Windows API Q291575 HOWTO: Use Visual Basic to Locate CD-ROM Drives Q196141 PRB: Problems Using Intrinsic File System Controls The Visual Basic Programmer's Guide (available on MSDN Online, http://msdn.microsoft.com/default.asp) (c) Microsoft Corporation 2001, All Rights Reserved. Contributions by Gray McDonald, Microsoft Corporation Additional query words: VB GetLogicalDriveStrings Drives Enumerate Letter ====================================================================== Keywords : kbsample kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 Version : :5.0,6.0 Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.