[erlang-questions] clarify: run_erl and ssh

Bengt Kleberg bengt.kleberg@REDACTED
Fri Dec 21 13:08:54 CET 2012

FWIW, I did not get "-t" to work. The problem persisted. Probably a
mistake on my part.

Adding TERM=vt100 in front of my real start command ("afile" is just an
example) was worse. Erlang did not start at all. Again, probably a
mistake on my part.

I will add a comment in the code about both possibilities so that it can
be looked into when time permits.


On Fri, 2012-12-21 at 11:59 +0100, Patrik Nyblom wrote:
> Hi Per!
> On 12/20/2012 03:56 PM, Per Hedeland wrote:
> > Patrik Nyblom <pan@REDACTED> wrote:
> >> On 12/19/2012 08:37 AM, Bengt Kleberg wrote:
> > [snip]
> >>> sekic1152 [8:26am] [/home/eleberg] -> ssh sekic1152 ./afile
> > [snip]
> >> I guess the PTY does not get initialized correctly when you run via ssh.
> > Or rather, in the above command, there is no pty allocated *at all* on
> > 'sekic1152'. Try 'ssh -t sekic1152 ./afile' instead. 'man ssh'.
> Well, I was unclear or downright misleading.  I did not mean the ssh 
> pty, but the pty allocated by run_erl, which can be allocated and setup 
> regardless of the stdin/stdout/stderr situation when starting run_erl. 
> Or, regardless of everything *except* for the fact that it needs to get 
> a valid curses definition, which in turn relies on the terminal setting 
> (or TERM environment variable) of the shell that runs run_erl (which is 
> expected to match the terminal doing to_erl)...
> So ssh does not really need to have allocated a pty, we just need to 
> tell run_erl that it should act as if we are going to connect via a 
> VT100 (or xterm or something else that has a curses definition). The 
> actual pty of run_erl get's initialized correctly regardless, we just 
> does not get newshell if we do not have a valid TERM variable so we can 
> find a valid curses definition.
> That's why
> TERM=vt100 run_erl -daemon /tmp/eleberg/ /tmp/eleberg/ "exec erl"
> works, but the aforementioned script doesn't (or, really it works, you 
> just get the "oldshell").
> ssh -t also works, as you then get the TERM variable set properly - it 
> is inherited from the remote host in the terminal setup negotiation.
> So, saying that the pty did not get properly initialized was wrong, I 
> take that back.
> Cheers,
> /Patrik
> >
> > --Per Hedeland
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