openssh unix dev - Oct 2011 - Determining the port assigned by -R 0

It's difficult to programmatically determine the port dynamically assigned
by -R 0.  The port is output in plain (and presumably localized) text, but
I've found that by far the most common use of this is for scripts.

Is there currently any sane way to get this information?  For the short term
I'll probably just parse the plaintext "Allocated port..."
message, but
that's obviously not a reliable solution.  It would be helpful if a list of
forwarded ports was stored in a parsable environment variable, as with
SSH_CLIENT.

-- 
Glenn Maynard

On Fri, 14 Oct 2011, Glenn Maynard wrote:
> It's difficult to programmatically determine the port dynamically
assigned
> by -R 0.  The port is output in plain (and presumably localized) text, but
> I've found that by far the most common use of this is for scripts.
> 
> Is there currently any sane way to get this information?  For the short
term
> I'll probably just parse the plaintext "Allocated port..."
message, but
> that's obviously not a reliable solution.  It would be helpful if a
list of
> forwarded ports was stored in a parsable environment variable, as with
> SSH_CLIENT.
It's easier if you use the multiplexing socket. 

ssh -O forward -R0:xxx:yyy host

will print the allocated port to stdout on success.