Networking on Windows 9x/ME - C / C++ / MFC Discussion Boards

How to tell if a file is open by someone else

GeraldoLuiz22-Jan-04 0:51

22-Jan-04 0:51

I have a program that manages documents on a central area in the network and I need to tell if a file is in use by someone ele, when I try to open it. The program runs on each machine that access the central archive (no program runs on the server that holds the files). What is the right or the best way to do it ? Can I try to lock the file or rename it and see by the error returned if the file is open ? Is there any API function that tells me that ? If it´s a Word Doc, for instance, the Word gives me a hint, but Notepad doesn´t. I want to send my own msg to the user, despite of the app used to open the file. Is it possible ?

Re: How to tell if a file is open by someone else

фил22-Jan-04 2:35

фил

22-Jan-04 2:35

check out sdk's CreateFile() proc. if specified file is somehow locked, you get an invalid handle. you may then call GetLastError():

hope this helps...

Re: How to tell if a file is open by someone else

basementman22-Jan-04 12:02

basementman

22-Jan-04 12:02

or you could look at good old _sopen, passing the _SH_DENYRW flag

onwards and upwards...

copy exe file to remote system

skpanda22-Jan-04 0:43

skpanda

22-Jan-04 0:43

hello,
i want to install my application (.exe) in a remote m/c. how to first copy the exe file to the remote m/c... .i know that a service is required to install & start in the remote m/c . now i want to install that remotely . how do i achieve that.???? please tell me how to install the application remotely ...i need it urgent.

please send code , article... urls...

Re: copy exe file to remote system

David Crow22-Jan-04 2:56

David Crow

22-Jan-04 2:56

skpanda wrote:
how to first copy the exe file to the remote m/c

How about CopyFile(), MoveFile(), or SHFileOperation()?

For the rest, it sounds like you'll need RPC.

A rich person is not the one who has the most, but the one that needs the least.

Bug in C++ ????

GDavy21-Jan-04 23:39

GDavy

21-Jan-04 23:39

Hello guys,

I think there is a bug in C++.
I had a very strange bug in my app but I fixed it..
What happened was somewhere in my code I wrote:

CString sTemp;
...//doStuff
sTemp = ((A_INTEGER == myObj.GetIntValue())? GetString("1"):GetString("2"));

...do more stuff

What happened now was that I used that sTemp string to put text in a list-control...
when I used the statement shown above and R1C2(Row1Column2) was filled with GetString("2") and R2C2 was filled with GetString("1") then in R1C5 the leftmost character was deduced by 1... When also R3C2 was filled with GetString("2") then R1C5 was deduced by 2 and so on...
in the other way no bug appeared....

The ONLY change I made in the code was that I replaced the line:`
sTemp = ((A_INTEGER == myObj.GetIntValue())? GetString("1"):GetString("2"));
with:
if(A_INTEGER == myObj.GetIntValue())
sTemp = GetString("1");
else
sTemp = GetString("2");
Which is still basically the same thing just in a different notation...
Does anyone know why this bug appeared?????

Any comments are welcome....

Greetings,
A puzzled programmer....

Re: Bug in C++ ????

фил22-Jan-04 2:42

фил

22-Jan-04 2:42

first of all c ain't software, so it cannot contain any bugs.
this maybe sth caused by your compiler.

have you checked out this:
sTemp = GetString((A_INTEGER == myObj.GetIntValue())? "1" : "2");

??

Networking on Windows 9x/ME

YanezDeGomeyra21-Jan-04 23:01

YanezDeGomeyra

21-Jan-04 23:01

Hi,

I need to write an application that is able to access the network as soon as networking is available. On NT class systems that's not a problem, I can just have a service and the network is available as soon as the machine boots up, be it an http address or a UNC path.

On 9x the problem is a bit trickier. I can still have an application that behaves like a service and that's run as soon as the computer boots up, but I am not able to access UNC paths until the user has loggend on into the network.

So the question is: is there a way to detect when the user logs on to the network (be it a callback, a message broadcasted, and event, whatever)? I could possibly hook on the logon window and intercept the clicking of 'OK', but that only starts the logging on and I don't know how long that takes.

Any ideas?

Thanks,
Alberto

Re: Networking on Windows 9x/ME

Mukkie25-Jan-04 8:16

Mukkie

25-Jan-04 8:16

Hello!

Try to catch message WM_DEVICECHANGE with DBT_DEVTYP_NET

Hope that it will help.

how to make CButton with bgcolor and a icon

angu selvam21-Jan-04 22:53

angu selvam

21-Jan-04 22:53

hai everybody,
I am doing a project in VC++.
for that i have came accross a trouble.
How to draw a CButton with a backcolor and
a icon on that button.

Re: how to make CButton with bgcolor and a icon

wb22-Jan-04 0:04

22-Jan-04 0:04

try

http://www.codeproject.com/buttonctrl/
Smile | :)

FindFirstChangeNotification

Rob Caldecott21-Jan-04 22:32

Rob Caldecott

21-Jan-04 22:32

Interesting issue when using FindFirstChangeNotification and FILE_NOTIFY_CHANGE_FILE_NAME.

I have two threads. Every so often thread A creates a temp file and then uses the MoveFile API command to move the file to a specific folder. Thread B is watching said folder via FindFirstChangeNotification/FILE_NOTIFY_CHANGE_FILE_NAME. When the file appears in the folder, thread B wakes up and processes the file. However, on some PCs, thread B fails to open the file - GetLastError returns 32 - "File in use by another process". I can only imagine that thread B is getting FILE_NOTIFY_CHANGE_FILE_NAME mid-way through the MoveFile. Not sure what to do about this - keep trying to open the file until it succeeds? Tacky. Note I am only getting one FILE_NOTIFY_CHANGE_FILE_NAME notification - so I can't ignore it if the file open fails in the hope I will get another one later.

Stumped. I guess, as this is one app, thread A can call a therad-safe function in thread B and add the file to a list protected by a critical section or something, but this is a fair amount of re-engineering.

Anyone else come across issues like this with FindFirstChangeNotification?

The Rob Blog

Re: FindFirstChangeNotification

Rob Manderson21-Jan-04 23:37

Rob Manderson

21-Jan-04 23:37

I haven't hit this using FindFirstChangeNotification but I've hit similar problems. I wouldn't keep trying to hit the file until success - as you say, that's tacky.

I've done this only in timed loops - a call to WaitForSingleObject or a call to WaitForMultipleObjects where the loop was intended to run every so often. I've always treated a fail on error 32 as a benign failure and left it to future passes through the loop to handle it.

I notice you say you can't ignore the error because you won't see the notification again. How about launching a thread to monitor the file? You could monitor multiple files in the one thread with reasonable (for your application) sleeps between passes over the locked files.

Rob Manderson

http://www.mindprobes.net

Paul Watson wrote:What sense would you most dislike loosing?

Ian Darling replied.

Telepathy

Then I'd no longer be able to find out everyones dirty little secrets The Lounge, December 4 2003

Re: FindFirstChangeNotification

Rob Caldecott21-Jan-04 23:56

Rob Caldecott

21-Jan-04 23:56

Rob, thanks for the response.

I want to keep threads to a minimum as the app already spawns plenty, especially when busy. What I am really after is a reliable way to use FindFirstChangeNotification so I am notified when a new file appears in a folder AND is safe to open!

I think I am going to have to re-engineer the app to allow both threads access to a list of files...

The Rob Blog

Re: FindFirstChangeNotification

Rob Manderson22-Jan-04 0:11

Rob Manderson

22-Jan-04 0:11

I understand the reluctance to spawn yet another thread. The situation I found myself in was that our application processed a file and then deleted it. Often the file wouldn't delete because some other process had an open handle on it so we had to defer the deletion. My solution was to write a class CDeferredFileDelete that tried to delete the file. If it succeeded well and good. If not, it passed the filename to a service and forgot about it. The service was then responsible for deleting the file at some future time. Hmmm maybe I have an idea for another article Smile | :)

In the situation I'm talking about it was relatively simple - the file was marked for deletion and it didn't much matter when the delete occurred just as long as it did occur. Your situation is somewhat different and I don't really know how (short of a seperate thread) to determine that a new file has appeared and is safe to open.

I think I'd approach it by using the notification to add a file object of some sort to a queue controlled by another thread, and have that thread try to open the file in exclusive mode. If success, close the file and add it to a work queue. If fail, try again in the next pass through the loop. Which is not much different from what I've already suggested Smile | :)

I can't think of a better approach.

Rob Manderson

Paul Watson wrote:What sense would you most dislike loosing?

Ian Darling replied.

Telepathy

Then I'd no longer be able to find out everyones dirty little secrets The Lounge, December 4 2003

Re: FindFirstChangeNotification

Rob Caldecott22-Jan-04 0:23

Rob Caldecott

22-Jan-04 0:23

Mmmm. OK, now I have a number of ideas:

1. Change the application so that after calling MoveFile, thread A calls a function that adds the filename to a list (protected by a critical section) and then signals thread B. Thread B wakes up, copies the list contents and processes each file. An even simpler solution would be for thread A to signal thread B - "a new file has been created" and for thread B to enumerate the files in the folder. Any that can't be opened can be ignored as the thread will be signalled for these again soon anyway.

2. Attempt to open the file and if error 32, sleep for a while and try again. However, what if the file beings moved is big (these files could easily be MBs). Would I get a notification when the file is first created or when MoveFile has almost finished?

3. Stick to current scheme but when thread B wakes up, have thread C monitor each file waiting until it can be opened (I guess using a timer). When the file can be opened, add to some list.

I'll experiment. Keeping it simple is usually best, so I think I will start by dropping FindFirstChangeNotification and having thread A set some event that thread B is waiting on when a file has been moved...

Thanks for the help guys.

The Rob Blog

Re: FindFirstChangeNotification

Rob Manderson22-Jan-04 0:33

Rob Manderson

22-Jan-04 0:33

I'd always go for simplest Smile | :)

You can't rely on when the file notification will occur (I think it happens shortly after the file is created for the simple reason that the filesystem has no knowledge about how long the file will be or how long it will be open). Since you can't rely on the file being exclusively available when you get the notification it seems simplest to throw the notification to a monitor thread that will tell your main app when the file really is exclusively available.

Hmmm, after a moments reflection, it seems to me that the only way to be absolutely sure is to have the monitor thread open the file exclusively and throw the HANDLE to the main app thread.

Rob Manderson

Paul Watson wrote:What sense would you most dislike loosing?

Ian Darling replied.

Telepathy

Then I'd no longer be able to find out everyones dirty little secrets The Lounge, December 4 2003

Re: FindFirstChangeNotification

basementman22-Jan-04 12:08

basementman

22-Jan-04 12:08

Wouldn't it just be simpler to create an IOCompletionPort and have thread B wait with a

// block on the I/O completion port (wait for a request)<br />
while (GetQueuedCompletionStatus(pLightningServer->m_hIOCompletionPort,(ULONG *)&pECB,&pUnused,&pOverlapped,INFINITE))<br />
  {<br />
    if (pOverlapped == (OVERLAPPED *)0xFFFFFFFF)<br />
      break;  // this is our signal that the server is shutting down.<br />
    <br />
    // now, process the file...<br />
  }

and then thread A would simply post the file name to the IOCompletionPort when the copy is complete.

Simple, clean, and resource friendly...

onwards and upwards...

Re: FindFirstChangeNotification

Rob Manderson22-Jan-04 12:35

Rob Manderson

22-Jan-04 12:35

Hmmm you may be right Smile | :)

I really have to study up on IO Completion Ports

Rob Manderson

Paul Watson wrote:What sense would you most dislike loosing?

Ian Darling replied.

Telepathy

Then I'd no longer be able to find out everyones dirty little secrets The Lounge, December 4 2003

Re: FindFirstChangeNotification

basementman23-Jan-04 4:21

basementman

23-Jan-04 4:21

They are really pretty straightforward and provide a nice queueing mechanism. The problem is that most people don't think of them unless they are doing actual I/O or thread pooling.

onwards and upwards...

Re: FindFirstChangeNotification

Yogurt22-Jan-04 0:01

Yogurt

22-Jan-04 0:01

Hi,

I've met the same issue. My work-around was to Sleep for a small amount of time (say, 100 ms) and retry the file opening only once. Not the nicest way but it seems to work for a long time.

toolbar on CDialogBar???

Balkrishna Talele21-Jan-04 22:23

Balkrishna Talele

21-Jan-04 22:23

Hello,
Is it possible to have toolbar on CDialogBar, while my CDialogBar in on CRebar..
the code is as follows
private :
CStatusBar m_wndStatusBar;
CToolBar m_wndToolBar;
CMyDialogBar m_wndDialogBar;
CReBar r1 ;
CBitmap bitmap;

.
.
.
r1.Create(this);

!m_wndDialogBar.Create(IDD_DIALOGBARX,this)
m_wndToolBar.CreateEx(this, WS_CHILD|TBSTYLE_FLAT | TBSTYLE_TRANSPARENT ));
m_wndToolBar.LoadToolBar(IDR_MAINFRAME);
.
.
r1.AddBar(&m_wndDialogBar, "Second Rebar" ,0,RBBS_GRIPPERALWAYS | RBBS_CHILDEDGE ) ;
r1.AddBar ( &m_wndToolBar, "First Rebar" ,0,RBBS_GRIPPERALWAYS | RBBS_CHILDEDGE ) ;

Now what I want is toolbar on Dialog Bar..while my dialog bar in on Rebar..is it possible, if so How???
regards
Balkrishna Talele

Please help

30jenny21-Jan-04 22:21

30jenny

21-Jan-04 22:21

Dear All,

Pls help me as am a novice to programming especially in VC and don’t know how to mask a voice using FFT. Is there any other way throurh which I can change or mask the voice. Or anyother code through which i be able to mask or change the voice. (.wav file) Or any function which can change the pitch of the wav file.

Pls I need ur help badlly as am running out of time for my final project.

Kind regards
Jenny

Re: Please help

Mukkie25-Jan-04 8:20

Mukkie

25-Jan-04 8:20

Hello!

Take a look maybe at DirectX API, but probably You will not find interesting functions there. Look at http://sourceforge.net , make some searches over net.

Probably not very helpful, but anyway :P

opening a doc in IE

Abhi Lahare21-Jan-04 22:19

Abhi Lahare

21-Jan-04 22:19

Hi ALL.

How i can open doc file in IE Broswer? I don't want to use any scripting language. can any point me in right direction?

Thanks in adavnce

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.