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From: neilsolent on 28 May 2008 16:07
I am using the CreateProcess() function to create a child process that
writes its stdout to a file.

I am opening the output file in the parent process, then passing it to
the child via the lpStartupInfo parameter of CreateProcess(), and by
specifying TRUE for the bInheritHandles parameter.

This works fine, except that the child process also inherits handles
that I don't want it to - for example sockets that the parent process
may have open!

Is there a way (of achieving a child process writing to stdout to a
file) without setting bInheritHandles to TRUE?

thanks,
Neil
From: Doug Harrison [MVP] on 28 May 2008 16:20
On Wed, 28 May 2008 13:07:35 -0700 (PDT), neilsolent
<neil(a)solenttechnology.co.uk> wrote:

>I am using the CreateProcess() function to create a child process that
>writes its stdout to a file.
>
>I am opening the output file in the parent process, then passing it to
>the child via the lpStartupInfo parameter of CreateProcess(), and by
>specifying TRUE for the bInheritHandles parameter.
>
>This works fine, except that the child process also inherits handles
>that I don't want it to - for example sockets that the parent process
>may have open!
>
>Is there a way (of achieving a child process writing to stdout to a
>file) without setting bInheritHandles to TRUE?

It's possible to specify that handles won't be inherited when you create
them. See for example CreateFile's lpSecurityAttributes parameter. Beyond
this, to disallow inheritance in CreateProcess, I believe the child process
would have to assist in the handle transfer in some scheme involving
DuplicateHandle.

--
Doug Harrison
Visual C++ MVP
From: neilsolent on 28 May 2008 16:38

> It's possible to specify that handles won't be inherited when you create
> them. See for example CreateFile's lpSecurityAttributes parameter. Beyond
> this, to disallow inheritance in CreateProcess, I believe the child process
> would have to assist in the handle transfer in some scheme involving
> DuplicateHandle.

Thanks Doug. I know I can specify handles to not be inherited, but
that would be messy coding to be honest (for example, there might be a
handle implicity created inside a function that isn't immediately
obvious).

From: Norman Bullen on 28 May 2008 21:18
neilsolent wrote:
> I am using the CreateProcess() function to create a child process that
> writes its stdout to a file.
>
> I am opening the output file in the parent process, then passing it to
> the child via the lpStartupInfo parameter of CreateProcess(), and by
> specifying TRUE for the bInheritHandles parameter.
>
> This works fine, except that the child process also inherits handles
> that I don't want it to - for example sockets that the parent process
> may have open!
>
> Is there a way (of achieving a child process writing to stdout to a
> file) without setting bInheritHandles to TRUE?
>
> thanks,
> Neil
Do you have access to the code for the child process? Is so, you can
simply pass the name of the output file as a command line parameter and
modify the process so that it opens the file and writes to it as a file
rather than as standard output. (There are also C and C++ library
functions which can link the handle of an open file to the standard
output name.)

If you can't modify the child process, create an intermediate child
process which simply opens a file the name of which is a command line
parameter with inherit ability enabled and then calls CreateProcess() to
start the original child process.

--
Norm

To reply, change domain to an adult feline.

From: neilsolent on 29 May 2008 04:09

> If you can't modify the child process, create an intermediate child
> process which simply opens a file the name of which is a command line
> parameter with inherit ability enabled and then calls CreateProcess() to
> start the original child process.

I can't modify the child process - user supplied scripts

An intemediary - that's a good idea - hadn't thought of it. Suspect
that is quite a common approach. I might give that a go.

I can't believe how difficult it is to do something that seemed so
simple!
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