Prev: exec - problem with stderr
Next: Is there a reason that ActiveTcl does not have an 64bit distribution?
From: Neil on 16 Jul 2010 19:46
>> But this raises to another question : is it possible to check whether
>> a file is still opened by another program ?

Which raises another question: does the program keep the file open? If
it just pipes text into it, or opens and closes it for every write, it
may close it and expect to be able to open it again (eg, createfile
with dwCreationDisposition of OPEN_EXISTING; which would cause issues
like you describe.)
http://msdn.microsoft.com/en-us/library/aa363858%28VS.85%29.aspx

Essentially, you check file handles to see if a file is open; but
you'd need to test it to see if it still breaks. Assuming it uses a
handle...which isn't guaranteed.

> I don't think Windows has any qualms
> about multiple programs accessing a file simultaneously for reading,

It depends on how a file is opened. If you call CreateFile internally,
you have lots of locking options:
http://msdn.microsoft.com/en-us/library/aa363874%28v=VS.85%29.aspx

Here's a snippet that might do what you want: regedt32 in XP merely
launches regedit and returns. This snippet launches regedt32, then
waits for regedit to terminate before it continues. I ran it, it
works. It's very simple.

package require twapi
exec regedt32.exe
while {[string length [::twapi::get_process_ids -name regedit.exe]]}
{;}
puts "Grandchild has exited"

You're guaranteed that by the time process child returns, process
grandchild will already be running, and that when process grandchild
terminates, your text file is moot.

You could do it without twapi, if you needed. (eg: tasklist | find
"regedit")

HTH
From: Alexandre Ferrieux on 17 Jul 2010 05:56
On Jul 16, 5:07 pm, "S-Y. Chen" <shenyeh_c...(a)hotmail.com> wrote:
>
> > PS: if you really can't do otherwise, try adding to the end of your
> > matlab script (before exit) something that creates yet another
> > signalling file, after closing the result file. This way, by
> > monitoring the second one you're sure that the first is closed.
>
> I have been thinking about creating another dummy file in the end of
> matlab too. But, just in case, if the loop come back faster then the
> file being closed by matlab, it will cause problem again.
> Any hint ?

Read again my suggestion: it is about creating the signalling file
with an instruction inside the matlab script. So the "loop coming
back" (more precisely, the matlab script returning) implies this
instruction has been executed. No race here.

-Alex

First  |  Prev  | 
Pages: 1 2
Prev: exec - problem with stderr
Next: Is there a reason that ActiveTcl does not have an 64bit distribution?