HOWTO: Get Extended File Time Information Using the Win32 API

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0
• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 32-bit only, for Windows, version 4.0

SUMMARY

Windows NT and Windows 95 store additional information about a file, including the time and date that the file was last accessed. This information cannot be accessed with the FileDateTime API function but can be extracted using a combination of calls to the Windows API. This article describes how to accomplish this behavior.

MORE INFORMATION

The creation time, last-written time, and the last-accessed (read) time of a file are all stored in 32-bit Windows, but only the time and date of the last write to the file are accessible directly from Visual Basic.

The API function used expects to be passed a system file handle rather than a Visual Basic file number. However, due to a limitation in 32-bit Visual Basic, the FileAttr function is incapable of returning an operating system file handle and API calls must be used to open the file. To obtain this data, do the following:

1. Start a new Visual Basic project. Form1 is created by default.

2. Add a text box control to Form1. It is called Text1 by default.

3. Add a CommandButton to Form1. It is called Command1 by default

4. Add the following code to the General Declarations section of Form1:

   Option Explicit

   Private Const OF_READ = &H0 Private Const OF_SHARE_DENY_NONE = &H40 Private Const OFS_MAXPATHNAME = 128

   Private Type OFSTRUCTREC

        cBytes As Byte
        fFixedDisk As Byte
        nErrCode As Integer
        Reserved1 As Integer
        Reserved2 As Integer
        szPathName(OFS_MAXPATHNAME) As Byte
   

   End Type

   Private Type FILETIMEREC

        dwLowDateTime As Long
        dwHighDateTime As Long
   

   End Type

   Private Type SYSTEMTIMEREC

        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

      Private Declare Function FileTimeToSystemTime Lib "kernel32" _
        (lpFileTime As FILETIMEREC, lpSystemTime As SYSTEMTIMEREC) As Long
      Private Declare Function GetFileTime Lib "kernel32" (ByVal _
        hFile As Long, lpCreationTime As FILETIMEREC, lpLastAccessTime _
        As FILETIMEREC, lpLastWriteTime As FILETIMEREC) As Long
      Private Declare Function OpenFile Lib "kernel32" (ByVal lpFileName As _
        String, lpReOpenBuff As OFSTRUCTREC, ByVal wStyle As Long) As Long
      Private Declare Function hread Lib "kernel32" Alias "_hread" _
        (ByVal hFile As Long, lpBuffer As Any, ByVal lBytes As Long) As Long
      Private Declare Function lclose Lib "kernel32" Alias "_lclose" (ByVal _
        hFile As Long) As Long
   
      Sub Form_Load()
        Command1.Caption = "&Get file access time"
        Text1.Text = "C:\AUTOEXEC.BAT"
      End Sub
   
      Private Sub Command1_Click()
        Dim sInpFile As String
        Dim hFile As Integer
        Dim FileStruct As OFSTRUCTREC
        Dim iRC As Integer
        Dim CreationTime As FILETIMEREC
        Dim LastAccessTime As FILETIMEREC
        Dim LastWriteTime As FILETIMEREC
        Dim SystemTime As SYSTEMTIMEREC
        sInpFile = Trim(Text1.Text)
        ' check that the file exists
        If Len(Dir(sInpFile)) = 0 Then
          MsgBox "Can't find the file", vbExclamation
          Exit Sub
        End If
   
        ' Open it to get a stream handle
        hFile = OpenFile(sInpFile, FileStruct, OF_READ Or OF_SHARE_DENY_NONE)
        If hFile = 0 Then
          MsgBox "Can't open the file", vbExclamation
          Exit Sub
        End If
   
        If GetFileTime(hFile, CreationTime, _
            LastAccessTime, LastWriteTime) Then
              ' massage time into format that we can use
          If Not FileTimeToSystemTime(LastAccessTime, SystemTime) Then
            Print "Year of file  :" & SystemTime.wYear
            Print "Month of File :" & SystemTime.wMonth
            Print "Day of File   :" & SystemTime.wDay
          Else
            MsgBox "FileTimeToSystemTime Failed"
          End If
        Else
          MsgBox "GetFileTime Failed"
        End If
   
        iRC = lclose(hFile)
      End Sub
   
   

5. Run the program by pressing the F5 key or clicking the Play button. Enter a filename in the text box, including path if necessary, and click the CommandButton.

The FAT and New Technology file systems support the file creation, last access, and last write time values. Under Windows 95, the precision of the time for a file in a FAT file system is 2 seconds. The time precision for files in other file systems, such as those connected through a network, depends on the file system but may also be limited by the remote device.

REFERENCES