I haven't tried this, but probably what you can do is try to open the
file exclusively (fmShareExclusive). If it is in use by DOS, then
the open should fail. Once DOS finishes and closes the file, the
open should succeed. So something like this:
waiting := 100;
repeat
try
fs := tFileStream.create (D+'harbor.txt', fmOpenRead or
fmShareExclusive);
// at this point the open succeeded, so break out of the loop
fs.destroy;
break;
except
// we get here if the file was not openable, or does not exist
sleep (100);
end;
dec (waiting);
until waiting <= 0;
if waiting <= 0 then error...
The above is OTTOMH. I think also, in case there is an old version
of harbor.txt on the hard drive, that it would make sense to delete
the file before running the DOS command, otherwise the
tFileStream.create might just succeed on the old file before the DOS
session gets underway.
BTW, should
'/c '+'ipconfig/all > harbor.txt'
be instead
'/c '+'ipconfig/all > ' + D + 'harbor.txt'
?
HTH
At 09:07 AM 7/6/2006, Rich Cooper wrote:
>Thanks Rob,
>
>But actually, I did get one to work. It finally gelled for the following
>code in my OnFormCreate handler:
>
> D := GetStartDir;
> ShellExecute( 0, 'open', PChar('command.com'),
> PChar('/c '+'ipconfig/all > harbor.txt'),
> nil, SW_HIDE );
> Waiting := 100;
> while ( (Waiting>0) and (not FileExists(D+'HARBOR.TXT')))
> do begin
> Sleep(250);
> Waiting := Waiting-1;
> end;
>
> if (not FileExists(D+'HARBOR.TXT'))
> then raise Exception.Create('Login Error 1.');
>
>But there is still a problem. The 'Waiting' loop discovers that the
>file exists, but not whether it has been completely written and let
>loose to be read. In my OnFormActivate handler, I use:
>
> if FirstActivation
> then begin
> D := GetStartDir;
> Application.ProcessMessages;
> Sleep(500);
>
> if FileExists(D+'HARBOR.TXT')
> then begin
> meHarbor.Lines.LoadFromFile(D+'HARBOR.TXT');
>
>which works MOST of the time. But occasionally, (5%) it causes
>an exception related to trying to read a file that is still being written.
>
>Does anyone have a way to determine whether the file HARBOR.TXT
>has been released for reading after being completely written? I would
>be able to fix this problem by replacing the Sleep(500) with a loop
>that tests till the HARBOR.TXT file is ready.
>
>Thanks,
>Rich
>
>
>Rob Kennedy wrote
>
> > Rich Cooper wrote:
> >> I'm trying to pipe a DOS command to a file using a ShellExecute,
> >> but it doesn't create the output file. Here's the code:
> >>
> >> var D : string;
> >> ...
> >> D := GetStartDir;
> >> ShellExecute(0,pChar('ipconfig/all >
> >> '),pchar('harbor.txt'),nil,pChar(D),SW_SHOWNORMAL);
> >> ...
> >>
> >> but no file named 'harbor.txt' gets created. Does anyone know how to
> >> fix this?
> >
> > First, "ipconfig/all >" is not a shell verb. Did you read the
> > documentation for ShellExecute before composing the code above?
> >
> > Second, you're telling ShellExecute to look in the registry for the
> > "ipconfig/all >" key for files named *.txt, and then execute the command
> > it finds there on the harbor.txt file, which I'm guessing doesn't even
> > exist.
> >
> > Third, note that command-line redirection is performed by the
> > command-line interpreter. ShellExecute is not a command-line
> > interpreter. Read this:
> >
> > http://blogs.msdn.com/oldnewthing/archive/2006/05/16/598893.aspx
> >
> > You should be able to find lots of example code to solve your problem
> > with the following search:
> >
> > http://groups.google.com/groups?q=pipe+dos+command&as_ugroup=*delphi*
> >
> > Fourth, ipconfig is not a DOS command. It's a console program, but it's
> > a fully fledged Windows program. Try to run it in DOS (if you even have
> > a computer with DOS installed anymore), and you'll simply be told that
> > it needs to run in Win32 mode.
> >
> > Finally, type-casting a string literal to PChar is not necessary and can
> > sometimes lead to problems. A string literal can be used as any
> > string-related type, including AnsiString, WideString, PAnsiChar, and
> > PWideChar. The compiler will choose based on what it needs. You don't
> > need to tell it.
> > --
> > Rob
Regards,
Sid Gudes
PIA Systems Corporation
[EMAIL PROTECTED]
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