How To Find Users Connected to an Access 7.0 Database

The Msldbusr.dll Functions

• LDBUser_GetUsers - After being called, this function returns two key pieces of information, the list of users and the number of users connected (if successful, otherwise returns an error number).
• LDBUser_GetError - Returns a string error message stating what the return value from LDBUser_GetUsers was.

Function Declarations

   #include <WINDOWS.H>

   typedef INT (WINAPI *PFNLDBUSERGETUSER)(LPSAFEARRAY FAR *, LPCSTR,
   INT);
   PFNLDBUSERGETUSER lpfnLdbUser_GetUsers;

   typedef BSTR (WINAPI *PFNLDBUSERGETERR)(INT);
   PFNLDBUSERGETERR lpfnLdbUser_GetError;
				

Function Parameters for C/C++

   INT LDBUser_GetUsers
   (
       LPSAFEARRAY FAR * lpsaUserList,         // Returned list of users
        LPCSTR            lpcstrMdbFilename,    // The name of the MDB file
        INT               nOptions              // Specifies return options
    )
				

      SAFEARRAY FAR*    psaUserList;
      SAFEARRAYBOUND    sabUserList[1];
      sabUserList[0].lLbound = 1;
      sabUserList[0].cElements = 1;
      psaUserList = SafeArrayCreate(VT_BSTR, 1, sabUserList);
					

    - 1 = All users who have logged in since the LDB file was created.
    - 2 = Only users who are currently logged in.
    - 4 = Only users who are causing the database file to be corrupt.
    - 8 = Just returns the count of users. No users are returned in the
          BSTR array.
					

   BSTR LDBUser_GetError
   (
       INT nError // The error number returned by LDBUser_GetUsers
   )
					

      -1 = Can't open the LDB file
      -2 = No user connected
      -3 = Can't create an array
      -4 = Can't redimension array
      -5 = Invalid argument passed
      -6 = Memory allocation error
      -7 = Bad index
      -8 = Out of memory
      -9 = Invalid Argument
     -10 = LDB is suspected as corrupted
     -11 = Invalid argument
     -12 = Unable to read MDB file
     -13 = Can't open the MDB file
     -14 = Can't find the LDB file
					

Sample Code

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

   typedef INT (WINAPI *PFNLDBUSER)(LPSAFEARRAY FAR *, PCSTR, INT );
   PFNLDBUSER lpfnLdbUser_GetUsers;

   typedef BSTR (WINAPI *PFNLDBUSERGETERR)(INT);
   PFNLDBUSERGETERR lpfnLdbUser_GetError;

   BOOL ShowUsers(char *);

   void main( int argc, char* argv[] )
   {
       if (argc != 2)
       return;

       ShowUsers(argv[1]);
   }

   // 
   // Display a list of JET users to the console screen.
   // 
   BOOL ShowUsers( char* pszDatabase )
   {
       HINSTANCE       hLdbUserInstance;
       SAFEARRAY FAR*  psaUserList = NULL;
       SAFEARRAYBOUND  sabUserList[1];
       int             cUsers;
       LONG            iLoop;
       HRESULT         hr;
       char*           szBuff;
       BOOL            fRetVal = TRUE;
       BSTR            bstrError = NULL;

   // Get the library instance handle.
       hLdbUserInstance = LoadLibrary("MSLDBUSR.DLL");
       if (!hLdbUserInstance)
           return FALSE;

   // Get a pointer to the main function in the library.
       lpfnLdbUser_GetUsers = (PFNLDBUSER)GetProcAddress(hLdbUserInstance,
           "LDBUser_GetUsers");
       if (!lpfnLdbUser_GetUsers)
   {
       fRetVal = FALSE;
       goto Exit;
   }

   // Get a pointer to the error function in case an error occurs.
   lpfnLdbUser_GetError = (PFNLDBUSERGETERR)GetProcAddress(
       hLdbUserInstance, "LDBUser_GetError");
   if (!lpfnLdbUser_GetError)
   {
       fRetVal = FALSE;
       goto Exit;
   }

   // Create a SAFEARRAY to hold the list of users.
   // NOTE: We'll only create a 1 element array because the
   // LDBUser_GetUsers will adjust the size if needed.
   sabUserList[0].lLbound    = 1;
   sabUserList[0].cElements  = 1;
   psaUserList = SafeArrayCreate(VT_BSTR, 1, sabUserList);

   // Make the function call and obtain the list of users.
   cUsers = lpfnLdbUser_GetUsers(&psaUserList, pszDatabase, 0x1);

   if (!cUsers )
   {
       printf("No users\n");
       goto Exit;
   }

   // Display error messages if any occurred.
   if (cUsers < 0)
   {
       bstrError = SysAllocString( lpfnLdbUser_GetError( cUsers ) );
       printf("Error #:%d -- %s\n",cUsers, bstrError);
       goto Exit;
   }

   // Display the list of users.
   for(iLoop=1;iLoop <= cUsers; iLoop++)
   {
       hr = SafeArrayGetElement(psaUserList, &iLoop, &szBuff);
       if (SUCCEEDED(hr))
           printf("User %d:%s\n",iLoop , szBuff);
       else
           printf("Failed on User %d\n",iLoop );
   }

   // Cleanup.
   Exit:
       if (bstrError)
           SysFreeString(bstrError);

       if (psaUserList)
           SafeArrayDestroy(psaUserList);

   // Free up the Msldbusr.dll.
       FreeLibrary(hLdbUserInstance);

       return TRUE;
   }