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Date: Fri, 6 Aug 2004 18:00:58 +0200 (CEST)
Subject: Re: Redirect stdout from SSH
From: "David E. Meier" <dev@eth0.ch>
To: "Cygwin List" <cygwin@cygwin.com>
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OK, short overview: I am working on a program in C# that needs to run some
commands on a remote machine and therefore I use SSH. The output will then
be written into a textbox. In C# you can run a command like this:

Process MyProcess = new Process();
ProcessStartInfo psi = new ProcessStartInfo();
psi.FileName = @"c:\cygwin\bin\ls";
psi.Arguments = "-al";
psi.UseShellExecute = false;
psi.RedirectStandardError = true;
psi.RedirectStandardOutput = true;
psi.CreateNoWindow = true;
MyProcess.StartInfo = psi;
MyProcess.Start();
+ textbox handling stuff.

This command will run 'ls' without creating the Command Window and outputs
the the listing of the direcotry as expected in the textbox. Now, when I
want to invoke SSH in the same manner, setting these values:

psi.FileName = @"c:\cygwin\bin\ssh";
psi.Arguments = "-i /path/to/key user@host ls -al";

then I have to explicitly set

psi.RedirectStandardInput = true;

or else it won't work. Although I see the command executing by observing
some network action there is nothing returned to the textbox and CPU stays
at 100%. There is nothing that needs to be written to stdin such as a
passphrase or so. However, programs using SSH, such as rsync, don't need
to set RedirectStandardInput = true to write their output to the textbox.
I just wonder what's the difference.

Dave.

> At 09:43 AM 8/6/2004, you wrote:
>>I got it working when standard input is also set to be redirected. Does
>>anyone have an explanation of this?
>
>
> No, sorry.  At least not without some details of what you did.  Like I
> said,
> the simple example I put together worked fine for me so it seems clear
> that
> there's a detail which is missing that accounts for the behavior you're
> seeing.  Did you try that example?  If you need me to, I can send the
> code,
> though it just invokes 'ssh' as you describe via 'system()'.
>
> If you can point to how your example is different than mine or provide a
> simple example that shows the problem, that might help.
>
>
>>> At 01:03 PM 8/3/2004, you wrote:
>>>>Hello list,
>>>>
>>>>I am writing a program in C# that calls some cygwin programs and
>>>> redirects
>>>>the standard output and error to a textbox. This works excellent with
>>>>calls like "ls -al" or rsync.
>>>>
>>>>However, I cannot read the output generated by SSH. When I issue a
>>>> command
>>>>like "ssh user@host ls -al" I can observe some network action but the
>>>>application stalls, uses 100% CPU and never spits out something. The
>>>> same
>>>>command in the cygwin shell executes with the result expected. Since I
>>>> use
>>>>public key authentication SSH is not waiting for any login information.
>>>>
>>>>Is this a configuration issue of SSH? Thanks for any help. Dave.
>>>
>>>
>>> Not AFAICS.  A small C program that invokes Cygwin's 'ssh' via
>>> 'system()'
>>> with 'ls -al' works fine for me.  Does that work for you?
>
> --
> Larry Hall                              http://www.rfk.com
> RFK Partners, Inc.                      (508) 893-9779 - RFK Office
> 838 Washington Street                   (508) 893-9889 - FAX
> Holliston, MA 01746
>
>
>


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