Q154821: HOWTO: Get Extended File Time Information Using the Win32 API
Article: Q154821
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.0,5.0,6.0
Operating System(s):
Keyword(s): kbAPI kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbGrpDSVB kbDSupport
Last Modified: 16-JUL-2001
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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
- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0
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SUMMARY
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Windows 2000, Windows NT, Windows Me, Windows 98, and Windows 95 store
additional information about a file, including the time and date that the file
was written to. 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 and last-written time of files are 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 last write 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(LastWriteTime, 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. Press the F5 key or click Play to run the program. Type a file name in the
text box, including path if necessary, and then click the CommandButton.
Note that the last written time is returned. The code could be extended to return
the Time information as well as the Date information shown. These values are
returned in the SYSTEMTIME record.
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
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The Win32 SDK has additional information about the APIs used in the code above.
Additional query words:
======================================================================
Keywords : kbAPI kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbGrpDSVB kbDSupport
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600 kbVB400Search kbVB400
Version : :4.0,5.0,6.0
Issue type : kbhowto
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