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Re: [Bug-XBoard] Remote shell problems

From: Tim Mann
Subject: Re: [Bug-XBoard] Remote shell problems
Date: Sat, 3 Apr 2004 14:12:52 -0800

Well, this is pretty annoying.  If you run "ssh -tt example.com
gnuchessx" from the command line and type ^C, the remote gnuchessx gets
a SIGINT as it should.  If you send a local ssh process a real SIGINT,
though, it prints "Killed by signal 2" and exits.  This is true
regardless of whether the local ssh was started directly from a shell
command line or by xboard.  I'm not sure how ssh is making the
distinction between hitting the key and sending the signal -- I'd have
to read the source code -- but the simple hack of having xboard send a
literal ^C character ('\003') down the pipe to ssh doesn't work either.

The only ways I see around this are either:

(1) Use rsh instead of ssh.  I realize rsh is not secure, but it's safe
enough if you are using it between two machines that are behind a

(2) Compile xboard with --disable-sigint.  This will work with just
about all chess engines, since hardly anyone really needs the SIGINT.
The only thing I know for sure needs it is GNU Chess 4 when run on a
Unix or Unix-like system that doesn't support FIONREAD.  (Linux for one
does support FIONREAD.)  No engines running on Windows can need it,
because it has never been implemented there.

It is tempting to make feature sigint=0 the default in the protocol,
which would keep this feature in existence but turn it off for any chess
engine that doesn't specifically request it.  This technically breaks
protocol backward compatibility.  That is, any old engine that needs
this feature would simply stop working; it wouldn't know that it had to
explicitly turn the feature on now.  Since I don't know of engines that
really need it, though, possibly this would be tolerable.

On Sun, 29 Feb 2004 18:19:10 +0100, PeteVine <address@hidden> wrote:
> On Sun, 29 Feb 2004 08:30:45 -0800
> Tim Mann <address@hidden> wrote:
> > Here's one thing to try, although if it's needed for any engine, I
> > don't understand why it would not be needed for crafty.  Since you
> > mention ssh, I assume you mean that you're using the -remoteShell ssh
> > command line option to xboard (or that you have it compiled in to use
> > ssh instead of rsh).  Either way, try doing -remoteShell "ssh -tt"
> > instead and see if that helps.
> Thanks for the suggestion but it made no difference.
> -- 
> PeteVine
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Tim Mann  address@hidden  http://tim-mann.org/

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