Tip 195: Modifying a File's Date and Time Stamp in Visual Basic 4.0
December 5, 1995
Abstract
In a Microsoft? Visual Basic? version 4.0 application, you may need to
modify the date and time stamp of a file. This article explains how this
can be accomplished.
Setting a New Date and Time Stamp for a File
To modify a file's date and time stamp in a Microsoft? Visual Basic?
version 4.0 application, you must perform several steps. First, you need
to call the Microsoft Windows? messaging application programming interface
(MAPI) SystemTimeToFileTime function. This function converts a system time
to a file time. The system time you want to convert must be stored in a
SYSTEMTIME structure. The converted time is then stored in a FILETIME
structure.
Next, you must use the Windows MAPI LocalFileTimeToFileTime function. This
function converts, as its name suggests, a local file time to a time that
is based on the Coordinated Universal Time (UTC). This newly converted
time information can then be used in your application by the Windows MAPI
SetFileTimeWrite function.
You must retrieve a handle to the file whose date and time stamp you want
to modify. This can be done by calling the Windows MAPI CreateFile
function. When you have the file's handle, a call to the SetFileTimeWrite
function actually updates the date and time stamp of the file.
Example Program
This program shows how to modify the date and time stamp of a file.
1. Create a new project in Visual Basic. Form1 is created by default.
2. Add the following code to the General Declarations section of Form1
(note that each Declare statement must be typed as a single line of
code):
Private Type FILETIME
dwLowDateTime As Long
dwHighDateTime As Long
End Type
Private 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
Private Const GENERIC_WRITE = &H40000000
Private Const OPEN_EXISTING = 3
Private Const FILE_SHARE_READ = &H1
Private Const FILE_SHARE_WRITE = &H2
Private Declare Function SetFileTimeWrite Lib "kernel32" Alias
"SetFileTime" (ByVal hFile As Long, ByVal MullP As Long,
ByVal NullP2 As Long, lpLastWriteTime As FILETIME) As Long
Private Declare Function SystemTimeToFileTime Lib "kernel32"
(lpSystemTime As SYSTEMTIME, lpFileTime As FILETIME) As Long
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA"
(ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal
dwShareMode As Long, ByVal lpSecurityAttributes As Long, ByVal
dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long,
ByVal hTemplateFile As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long)
As Long
Private Declare Function LocalFileTimeToFileTime Lib "kernel32"
(lpLocalFileTime As FILETIME, lpFileTime As FILETIME) As Long
3. Add a Command Button control to Form1. Command1 is created by default.
4. Add the following code to the Click event for Command1:
Private Sub Command1_Click()
Dim Year As Integer, Month As Integer
Dim Day As Integer, Hour As Integer
Dim Minute As Integer, Second As Integer
Dim TimeStamp As Variant
Dim Filename As String
Dim X As Integer
Year = 1996
Month = 1
Day = 1
Hour = 1
Minute = 0
Second = 0
TimeStamp = DateSerial(Year, Month, Day) + TimeSerial(Hour, Minute, Second)
Filename = "c:\autoexec.bat"
X = ModifyFileStamp(Filename, TimeStamp)
MsgBox "The time and date stamp was updated"
End Sub
5. Create a new function called ModifyFileStamp. Add the following code
to this function:
Function ModifyFileStamp(Filename As String, TimeStamp As Variant)
As Integer
Dim X As Long
Dim Handle As Long
Dim System_Time As SYSTEMTIME
Dim File_Time As FILETIME
Dim Local_Time As FILETIME
System_Time.wYear = Year(TimeStamp)
System_Time.wMonth = Month(TimeStamp)
System_Time.wDay = Day(TimeStamp)
System_Time.wDayOfWeek = WeekDay(TimeStamp) - 1
System_Time.wHour = Hour(TimeStamp)
System_Time.wSecond = Second(TimeStamp)
System_Time.wMilliseconds = 0
'convert the system time to a file time
X = SystemTimeToFileTime(System_Time, Local_Time)
'convert local file time to file time based on UTC
X = LocalFileTimeToFileTime(Local_Time, File_Time)
'open the file so we can get a file handle to the file
Handle = CreateFile(Filename, GENERIC_WRITE, FILE_SHARE_READ Or
FILE_SHARE_WRITE, ByVal 0&, OPEN_EXISTING, 0, 0)
'now change the file time and date stamp
X = SetFileTimeWrite(Handle, ByVal 0&, ByVal 0&, File_Time)
CloseHandle Handle
End Function
Run the example program by pressing F5. Click the Command Button control.
The date and time stamp of the AUTOEXEC.BAT file is immediately updated.
Additional References
"File Times." (Library, Product Documentation, SDKs, Win32 SDK,
Win32 Programmer's Reference, Overviews, Window Management,
System Services, Time, About Time)
"LocalFileTimeToFileTime QuickInfo Overview Group." (Library,
Product Documentation, SDKs, Win32 SDK, Win32 Programmer's Reference,
Reference, Functions, LoadAccelerators to LZInit)
"SetFileTime QuickInfo Overview Group." (Library,
Product Documentation, SDKs, Win32 SDK, Win32 Programmer's Reference,
Reference, Functions, SetBrushOrgEx to SetGraphicsMode)
"SystemTimeToFileTime QuickInfo Overview Group." (Library,
Product Documentation, SDKs, Win32 SDK, Win32 Programmer's Reference,
Reference, Functions, ShowCursor to UnhandledExceptionFilter)
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