Re: [ptxdist] Backspace not working in terminal (using ssh)

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Thu, Mar 21, 2019 at 12:46:40PM +0000, Ian Abbott wrote:
> On 20/03/2019 15:41, Michael Olbrich wrote:
> > On Wed, Mar 20, 2019 at 12:41:47PM +0000, Ian Abbott wrote:
> > > On 20/03/2019 09:15, Dold, Wolfram wrote:
> > > > On Tue, 2019-03-19 at 17:42 +0000, Ian Abbott wrote:
> > > > > On 19/03/2019 12:33, Dold, Wolfram wrote:
> > > > > > Hi Ian,
> > > > > > On Tue, 2019-03-19 at 12:06 +0000, Ian Abbott wrote:
> > > > > > > On 19/03/2019 09:17, Dold, Wolfram wrote:
> > > > > > > > Hi there,
> > > > > > > > when we connect via ssh to our embedded device, the backspace key does not work.
> > > > > > > > During the analysis we found out that the passage
> > > > > > > > 
> > > > > > > > # This fixes the backspace when telnetting in.
> > > > > > > > if [ "$TERM" != "linux" ]; then
> > > > > > > >             stty erase ^H
> > > > > > > > fi
> > > > > > > > 
> > > > > > > > from the file '/etc/profile' contained in ptxdist.
> > > > > > > > 
> > > > > > > > Now I want to ask, how best to fix this behavior?
> > > > > > > > Can the passage simply be omitted? (At least the comment lets me assume that, because there 'telnet' is
> > > > > > > > mentioned
> > > > > > > > and
> > > > > > > > that is no longer necessarily state of the art).
> > > > > > > > Or does omitting it lead to other unwanted side effects?
> > > > > > > > 
> > > > > > > > Any help would be appreciated.
> [snip because it's getting a bit long]
> 
> > > I've no idea why that bit of the /etc/profile file is there, but I guess it
> > > must have suited one of the PTXdist developers at the time.  A "git blame"
> > > only revealed that the whole file was added in 2006, so I don't know how
> > > relevant that part of it is today.
> > 
> > This code was moved around some more. It was actually introduced in the
> > initial import from CVS in 2003 :-). Telnet works just fine without this,
> > so I guess this is no longer needed.
> 
> Perhaps it was there for the Windows Telnet client which seems to send ASCII
> BS when the "Backspace" key is pressed and ASCII DEL when the (less
> conveniently placed) "Delete" key is pressed.  This mimics the codes sent by
> the VT-102 "Backspace" and "Delete" keys which were both conveniently
> placed.
> 
> The Windows telnet client has a -t option to set the terminal type to one of
> "vt100", "vt52", "ansi", or "vtnt", but it doesn't pass the selected
> terminal type to the server, and this doesn't seem to have any effect on the
> codes sent by the "Backspace" and "Delete" keys.  The TERM environment
> variable ends up getting set to "vt102" by default on my PTXdist systems if
> a terminal type hasn't been passed through by the Telnet client.  I don't
> know if that is configurable.
> 
> The Windows Telnet client isn't installed by default, but can still be
> installed as a "Windows Feature".  I guess most people who used it would
> have switched to something like PuTTY by now.

I'm pretty sure it was a Linux issue. I remember having problems like this
a long time ago.

> > I'll be happy to apply a patch that removes this.
> 
> I'm worried that doing so might annoy some people who expect the existing
> behavior.

I'd rather fix a real problem. If it causes issues, then we'll try to find
a solution.

Michael

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