Can I stop redirecting outputs?

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Hi,

In case of crash or what-not I want to be able to release the outputs from a process I and monitoring strOut and stdErr on. I get the feeling that uncoupling the listeners and then setting
_process.StartInfo.RedirectStandardError = false; isn't going to work.

Is it possible to stop redirecting the process outputs or do I have to redirect them elsewhere?

Thanks in advance ^_^

Posted 11-Jun-13 6:17am

Andy Lanng

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Sergey Alexandrovich Kryukov 11-Jun-13 12:33pm

"Crash" should mean process termination, right? In this case, everything locked by the process is anyway released. Or do you mean something else? Then please explain...
—SA

Andy Lanng 12-Jun-13 4:04am

I think that the issue is that the sub-process doesn't have anywhere to direct it's outputs once I have told it to redirect. It appears that 'releasing' the output streams doesn't actually mean that they are directed elsewhere and so they fill up and the process freezes. I'll test it out and post my results :D

Sergey Alexandrovich Kryukov 12-Jun-13 12:52pm

There is no such thing as sub-project, there is a child project, and it is no different form a completely independent process, with one trivial exclusion: your parent process "knows" exactly which process handle is the child's, as it is obtained from the first hand. This way, you can always, wait for child termination, kill it, get some information, etc. Also, you can set up re-direction of StandardOutput and StandardError the way you want, before starting the child. Do you know how to do it? and of course you need to make ProcessStartInfo.RedirectStandardError = false; (NOT _process.StartInfo)...
—SA

Andy Lanng 13-Jun-13 4:46am

Thanks for the comments. Yes I am reading the outputs async with BeginReadOutput(), having already set the event listener. I found CancelReadOutput() which was exactly what I was looking for (doh!).
I still don't understand why my child process froze when the parent did not. I think there is something fundamental with IIS processes (w3wp which is the parent) that meant that the child process (robocopy) became orphaned but still had its std's pointing at a process that was no longer reading them.
So far, I have included a dtor in the object that calls the child that will try to call CancelReadxxx(), but I may also ask it to kill the process.

Sergey Alexandrovich Kryukov 13-Jun-13 12:04pm

IIS process? Why? I makes me suspect that you might abuse something. Why using robocopy at all. Generally, starting a child process is a questionable practice, if not bad.
Now, processes are fully independent. If the child process goes wrong (it could hang without crashing and being terminated), it cannot directly affect another process, whatsoever (unless, say, the parent process uses some data from the chile process to screw up itself. What's to valuable in that process which you could not do in yours? Aren't you just wasting your time for uncertainties?
—SA

Andy Lanng 14-Jun-13 6:05am

This is all inherited code. Robocopy is faster for the purpose. The app is an in house Webapp for building, testing and delivering software products so there's a lot of moving files around. It hasn't reoccurred since the first instance so these mountains might actually be molehills.

Sergey Alexandrovich Kryukov 14-Jun-13 12:30pm

Inherited or not, you have to do something about it. I don't see why robocopy should be much faster, but you are loosing more on trying to cope with the separate process, which is often uneasy or unreliable, and time consuming, in terms of development and debugging, that's the point. Copying files is way too easy to trust it to external process and to have involved troubles with that.
—SA

2 solutions

Solution 1

This depends entirely on how you launched the process. Did you launch the .EXE directly or did you supply the .EXE as a command line argument and you launched it by launched CMD.EXE instead??

But, once the process crashes, the process is dead and so are the standard streams. There's nothing left to redirect, so the question is pointless.

Posted 11-Jun-13 14:45pm

Dave Kreskowiak

Updated 11-Jun-13 14:46pm

v2

Comments

Ron Beyer 11-Jun-13 20:58pm

I think what he means if he uses Process.Start, redirects the outputs of the external process to his process, then HIS process crashes.

Dave Kreskowiak 12-Jun-13 1:00am

Ah. I see, now that I've re-read the post.

Interesting. I can see why it would and wouldn't work at the same time. The only way to know for sure is to test it and see what happens.

Andy Lanng 12-Jun-13 4:02am

Ron was correct in his interpretation. I will test and post if I find a solution
Thanks ^_^

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Andy Lanng · Accepted Answer · 2013-06-11T23:52:00

DOH >_<<br mode="hold" />
Async start listening to channels:

C#

_windowsProcess.BeginOutputReadLine();
_windowsProcess.BeginErrorReadLine();

and to stop:

C#

_windowsProcess.CancelOutputRead();
_windowsProcess.CancelErrorRead();

I was looking for stop or end. This took me a while to find (guess I'm still no good at googling)

There are actually deeper issues but I already have a separate thread for that ( stdout and stderr Listener issues (causing frozen processes?)[^] )

Hopefully someone else will find this useful

Thanks all ^_^