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Detect a file change

kolarb
kolarb asked
on
Medium Priority
831 Views
Last Modified: 2012-08-13
How to detect a file has been changed using something like a shell extension or a hook...

(I don't want a TTimer with constantly checking if a file's date is any different)
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Commented:
For what do you want to know the change of the file?
 Progressbar for copy of file?

Why has it be checked the whole time?
You can do  this with setting Notification but only in WindowsNT. In WIndows95 this is impossible and you must use timer.

For WinNT i can write simple code.

Author

Commented:
ZifNab: When a user changes a file a program should be run. It is known which files should be looked at.

mirek: ?? check examples/demos/shellext examples in Delphi3. I thought something like that should be possible. Anyway show me your NT code and I'll reconsider your answer.
arh

Commented:
As far as i know, there is no shell extension of this kind. But there is a pair of API functions - FindFirstChangeNotificaion/FindNextChangeNotification, available in both win95 and NT, which will notify you when any file in a particular directory has been changed. You should determine which particular file in that directory was changed by examining its date/time or something like that.
And to receive such notification your program should be running
constantly in background.
Sorry, i can't give you an example now.
Thanx to arh !!!!

As "arh" write i try test if notification works on Win95.
I found so yes but with some limitations. I don't have enought time to test what working and what not working but this example working.

var stop : boolean;

procedure TForm1.Button1Click(Sender: TObject);
var
  dwWaitStatus   : DWORD;
  dwChangeHandle : THandle;
begin
  Stop := False;
  dwChangeHandle := FindFirstChangeNotification(
    'C:\',                        //  directory to watch
    FALSE,                        // do not watch the subtree
                                  // in Win95 You can't set this to true !!!!
    FILE_NOTIFY_CHANGE_DIR_NAME); // watch filename changes

  if dwChangeHandle=INVALID_HANDLE_VALUE then
    begin
      ShowMessage('I can''t set notification' );
      ExitProcess(GetLastError)
    end;
  while (stop=false) do
  begin
    dwWaitStatus := WaitForSingleObject(dwChangeHandle, 100);
    if dwWaitStatus=WAIT_OBJECT_0 then
      begin
        Memo1.Lines.Add( 'File Created, Renamed or Deleted in C:\' );
      //here you can compare previous list of files with current list of files
      //and find what was changed
        if FindNextChangeNotification(dwChangeHandle)=FALSE then
        begin
          ShowMessage('I can''t restart notification' );
          ExitProcess(GetLastError);
        end;
      end;
    Application.ProcessMessages;
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Stop := True;
end;



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Author

Commented:
Excellent!
Will try it now and grade the answer.

Author

Commented:
Thank you guys&gals.
Searched the MSDN and found this example with other settings.
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