bobby wrote:
Andrew Haines wrote:
Michalis Kamburelis wrote:
Andrew Haines wrote:
[...]
I am not extremely familiar with how streams work, but using
LoadFromStream(Output) may not "Read" the data so it can be
replaced with new data. Also as I said I think S.LoadFromStream is
blocking until the end of the stream is reached, which can't happen
until the program has ended possibly resulting in lost data.
Someone please correct me if I am wrong ;)
That's a good point, S.LoadFromStream *should* be blocking but
*currently it isn't*. I reproduced Bobby's problem with
TStringList.LoadFromStream (on Linux, so it's not specific to
Win32). Looking at implementation in rtl/objpas/classes/stringl.inc,
there's a test
Until BytesRead<>BufDelta
that should probably be changed to
Until BytesRead = 0
Then it should be possible to call S.LoadFromStream just once, and
read the whole output of a process. There should be no need to do
the partial reads, because TStringList.LoadFromStream should already
handle this. Generally, example "Reading large output" on
[http://wiki.lazarus.freepascal.org/index.php/Executing_External_Programs]
will not need to use memory stream anymore. One should just
construct process without poWaitOnExit (to prevent deadlock), and
then be able to read it's whole output using single call
AStringList.LoadFromStream(AProcess.Output);
So right now I think that what Bobby is observing is a result of a
bug in FPC's implementation of TStringList.LoadFromStream. I'll try
to fix it and submit to FPC devels.
Anyway, for now: the method of example "Reading large output" in the
wiki still works OK. In other words: Bobby, for now you should use
memory streams to read the pipe, like presented on the wiki (and
like Andrew suggests). Then, after grabbing everything to
TMemoryStream, you can safely convert it to e.g. TStringList by
AStringList.LoadFromStream(AMemoryStream);
This Should Work :)
I think that TProcess.Output cannot be larger than a certain size on
some platforms, so this is why it is read in increments rather than
waiting until it is done. Because the program will stop until some
output is read to make room for new output.
Andrew
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I already told you, the Lazarus Wiki example gives me the same results
like my code - 106kb and no byte more. I got the conclusion that the
Pipes are somehow limited to certain size of data.
As I can't go further with pipes (obviously), how can I execute
external app, and use the console's pipes to pipe the output?
Something like:
prog.exe [attr] > output.log
on linux in the unix unit there is fpsystem
fpsystem('blah > output.txt');
in windows there is shell or shellexec or similar. I don't have windows
here so I can't say for sure.
Andrew
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