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Date: Mon, 14 May 2007 13:15:06 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: rsync and tcsh don't play well on Cygwin
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On Apr 19 11:01, Mark Riley wrote:
> After having problems with rsync (2.6.6) hanging while pushing files
> to a Cygwin machine over ssh, I searched the lists here and found
> that many other users were experiencing the same problem.  While
> some solutions seemed to mitigate the problem, there are still some
> users experiencing this problem (myself included).
> 
> After wading through massive(!) strace output files, it appears that 
> an interaction between tcsh and rsync on the remote Cygwin machine
> is the culprit.  If the remote machine is configured to use bash as the
> login shell, then the problem disappears - rsync works fine.  This
> might explain why some users can't reproduce the problem (they don't
> use tcsh).
> 
> When rsync connects to the remote machine using ssh, sshd launches
> a login shell (tcsh in this case) before the remote rsync command is run.
> Perusing the source for tcsh, it can be seen that tsch calls setmode(fd,
> O_TEXT) on the pipe supplied to it by sshd.  When rsync is subsequently
> invoked, it inherits this pipe.  Rsync apparently assumes it is getting an
> O_BINARY pipe and fails miserably when \r\n combinations are
> translated to \n.
> 
> Recompiling rsync with
> 
>    setmode(STDIN_FILENO, O_BINARY);
>    setmode(STDOUT_FILENO, O_BINARY);
> 
> placed near the beginning of main() fixes the problem and I can now
> use tcsh as my login shell on the remote machine again.
> 
> This may not be the ideal solution, but other solutions I've tried like
> putting "binmode" in the CYGWIN environment variable on the remote
> machine or invoking rsync with the --rsh="ssh -T" option didn't
> help.
> 
> Anyway, I hope this solution works for some of the others out there
> experiencing this problem.

This is IMHO a problem in both applications, rsync and tcsh.  rsync
should always make sure that its IO on the pipe is binary (as you do
above, for instance), and tcsh shouldn't assume O_TEXT for all input.
The latter is something I plan to change for years, but I got always
distracted by other stuff.  Maybe this year?!?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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