Stephen Posey wrote:
> Rich Cooper wrote:
>> Thanks Stephen,
>>
>> I found a web page with a similar snippet, and so I was able to
>> get the following to work 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 95% of the time. But sometimes it causes the LoadFromFile
>> procedure to throw an exception related to trying to read a file that is
>> not yet ready to be read - still locked by the NT file system in XP, and
>> not
>> yet completely written to the HARBOR.TXT file and then released to
>> the rest of the computer.
>>
>> 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 for reading, having been
>> fully released.
>
> I don't know precisely how cmd.exe creates and opens a redirected file
> like that, but your attempting to open it in "exclusive share" mode
> ought to fail regardless if the file is still being written.
>
> You can use a TFileStream instance, like so:
>
> FS := TFileStream.Create(D + 'HARBOR.TXT',
> fmOpenRead or fmShareExclusive);
>
> Attempt that and catch any exception raised due to the sharing conflict
> (should be some form of EInOutError), if the file exists and no
> exception is raised on attempting to open it, then it should be finished.
>
> HTH
>
> Stephen Posey
> [EMAIL PROTECTED]
I tried "LoadFromFile()" with try ... except end around it and kept
looping till the exceptions went away - that worked just fine!
Thanks Stephen and Simon,
Rich
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