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

[Ian Abbott <abbotti@mev.co.uk>]

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'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.

-- 
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