Tip 198: Retrieving File Information in Visual Basic 4.0

December 5, 1995

Abstract

This article explains how, from within a Microsoft® Visual Basic® version 4.0 application, you can retrieve information about a specific file stored on disk. This information may include the date and time when the file was initially created, when the file was last accessed, and any number of other details.

Using the GetFileInformationByHandle Function

In some Microsoft® Visual Basic® version 4.0 applications you write, you may need to examine certain file information. For example, you may need to determine when a file was last accessed or the serial number of the volume that contains the file. This type of information about a file can be retrieved using the Microsoft Windows® application programming interface (API) GetFileInformationByHandle function.

To use the GetFileInformationByHandle function, you must include the following Declare statement in your project:

Declare Function GetFileInformationByHandle Lib "kernel32" (ByVal hFile 
   As Long, lpFileInformation As BY_HANDLE_FILE_INFORMATION) As Long

As you can see, this function requires only two arguments: the handle of the file you want to retrieve information on and the address of a BY_HANDLE_FILE_INFORMATION structure that will hold the file's information.

There are several steps you must perform to retrieve information about a file. First, you must use the Windows API OpenFile function to obtain the specified file's file handle. Once you have the file handle, you can call the GetFileInformationByHandle function. The file's information is then stored in the BY_HANDLE_FILE_INFORMATION structure. Next, you must use the Windows API CloseHandle function to release the file handle to the system.

In the example program below, you retrieve the date and time that the file was actually created. You then use the Windows API FileTimeToSystemTime function to convert the file's date and time stamp to individual values that you can use in the program. This same procedure is used to process the file's last access and last write date and time stamp. In addition, two other pieces of information are also retrieved about the file—the file's attributes and the volume's serial number.

Example Program

This program shows how to retrieve information about a specific file.

1. Create a new project in Visual Basic. Form1 is created by default.
   
   
2. From the Visual Basic Insert menu, select Module to create a new module. Module1.Bas is created by default.
   
   
3. Add the following code to Module1.Bas (note that each Declare statement must be typed as a single line of code):

   Declare Function OpenFile Lib "kernel32" (ByVal lpFileName As String, 
      lpReOpenBuff As OFSTRUCT, ByVal wStyle As Long) As Long
   Declare Function GetFileInformationByHandle Lib "kernel32" (ByVal hFile 
      As Long, lpFileInformation As BY_HANDLE_FILE_INFORMATION) As Long
   Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
   Declare Function FileTimeToSystemTime Lib "kernel32" (lpFileTime As FileTime, 
      lpSystemTime As SYSTEMTIME) As Long
   Public Const OFS_MAXPATHNAME = 128
   Public Const OF_READ = &H0
   Type OFSTRUCT
           cBytes As Byte
           fFixedDisk As Byte
           nErrCode As Integer
           Reserved1 As Integer
           Reserved2 As Integer
           szPathName(OFS_MAXPATHNAME) As Byte
   End Type
   Type SYSTEMTIME
           wYear As Integer
           wMonth As Integer
           wDayOfWeek As Integer
           wDay As Integer
           wHour As Integer
           wMinute As Integer
           wSecond As Integer
           wMilliseconds As Integer
   End Type
   Type FileTime
           dwLowDateTime As Long
           dwHighDateTime As Long
   End Type
   Type BY_HANDLE_FILE_INFORMATION
           dwFileAttributes As Long
           ftCreationTime As FileTime
           ftLastAccessTime As FileTime
           ftLastWriteTime As FileTime
           dwVolumeSerialNumber As Long
           nFileSizeHigh As Long
           nFileSizeLow As Long
           nNumberOfLinks As Long
           nFileIndexHigh As Long
           nFileIndexLow As Long
   End Type
   

4. Add a Command Button control to Form1. Command1 is created by default.
   
   
5. Add the following code to the Click event for Command1:

   Private Sub Command1_Click()
       Dim Ret As Long
       Dim FileHandle As Long
       Dim FileInfo As BY_HANDLE_FILE_INFORMATION
       Dim lpReOpenBuff As OFSTRUCT
       Dim FileTime As SYSTEMTIME
   
       FileHandle = OpenFile("c:\autoexec.bat", lpReOpenBuff, OF_READ)
       Ret = GetFileInformationByHandle(FileHandle, FileInfo)
   
       Ret = FileTimeToSystemTime(FileInfo.ftCreationTime, FileTime)
       Print "File created on " & FileTime.wYear, FileTime.wMonth, 
          FileTime.wDay
   
       Ret = FileTimeToSystemTime(FileInfo.ftLastAccessTime, FileTime)
       Print "File last accessed on: " & FileTime.wYear, FileTime.wMonth, 
          FileTime.wDay
   
       Ret = FileTimeToSystemTime(FileInfo.ftLastWriteTime, FileTime)
       Print "File last written to: " & FileTime.wYear, FileTime.wMonth, 
          FileTime.wDay
   
       Print "Volume Serial Number is: " & FileInfo.dwVolumeSerialNumber
       Print "File attributes are: " & FileInfo.dwFileAttributes
   
   
       Ret = CloseHandle(FileHandle)
   End Sub
   

Run the example program by pressing f5. Click the Command Button control. The program displays the file's creation date, last access date, and last write date, as well as the disk's volume serial number and the attributes associated with the file.

Additional References

"BY_HANDLE_FILE_INFORMATION QuickInfo." (MSDN Library, SDK Documentation, Platform SDK)

"File Times." (MSDN Library, SDK Documentation, Platform SDK)

"FileTimeToSystemTime QuickInfo Overview Group." (MSDN Library, SDK Documentation, Platform SDK)

"GetFileInformationByHandle QuickInfo Overview Group." (MSDN Library, SDK Documentation, Platform SDK)