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Re: Bug with svn+ssh (plus workaround)

From: Greg Hudson <ghudson_at_MIT.EDU>
Date: 2006-03-21 17:50:16 CET

On Tue, 2006-03-21 at 17:24 +0200, Alan Barrett wrote:
> I found a horrible interaction between subversion and ssh.

I blame Unix. O_NONBLOCK should be a file descriptor flag, like
FD_CLOEXEC is, not an open file description flag. I've run into this
kind of interaction in other contexts as well.

Given that Unix probably won't change (introducing FD_NONBLOCK and
defining its interactions with O_NONBLOCK would be pretty confusing, to
solve what is generally a small problem, and of course "Unix" is a dozen
different operating systems whose programmers don't talk to each other
much), I also blame ssh. You shouldn't set an fd non-blocking if it
might be shared with code you don't control, and there are alternatives
to non-blocking I/O.

Joseph Galbraith wrote:
> The reason not to do this is that ssh uses stderr to prompt
> for authentication credentials.

That would surprise me. I would expect it to use /dev/tty, since it has
to use that to read input from the user anyway (stdin is controlled by

Even if so, we would presumably just be funneling ssh's stderr pipe to
Subversion's own stderr.

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Received on Tue Mar 21 17:55:11 2006

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