[TUHS] Word erase?

[Mary Ann Horton]

On 4/8/24 08:18, arnold at skeeve.com wrote:
> Dan Cross<crossd at gmail.com>  wrote:
>
>> I wonder if anyone can shed any light on the timing and rationale for
>> the introduction of “word erase” functionality to the kernel terminal
>> driver. My surface skim earlier leads me to believe it came to Unix
>> with 4BSD, but it was not reincorporated into 8th Edition or later,
>> nor did it make it to Plan 9 (which did incorporate ^U for the "line
>> kill" command).  TOPS-20 supports it via the familiar ^W, but I'm not
>> sure about other PDP-10 OSes (Lars?).  Multics does not support it.
>> VMS does not support it.
>>
>> What was the proximal inspiration?  The early terminal drivers seem to
>> use the Multics command editing suite (`#` for erase/backspace, `@`
>> for line kill), though at some point that changed, one presumes as
>> TTYs fell out of favor and display terminals came to the fore.
>>
>>          - Dan C.
> My memory jibes with this -- through V7 defaults were # and @, and BSD
> changed to ^H / DEL and ^U.  ^W was a BSD thing, probably inspired by
> TOPS-10.
>
Vi had ^W for word erase long before the tty driver. It's documented in 
2BSD.

I think it appeared in the tty driver as part of the new tty driver, 
around 4.1C. The 4.2 stty(1) documents that you can set werase but only 
with the new tty driver.

Personally I fondly recalled it from Tenex and wished for it in UNIX. I 
can't recall if I lobbied for it or if anyone heard me.

Chambers and Quarterman noted the new tty driver's presence in 4.1C. 
https://gunkies.org/wiki/UNIX*_System_V_and_4.1C_BSD

> 2.2.5  Ioctls   The  ioctl  system   call   is   essentially
>            identical  in  the two systems.  The interesting differences
>            are in the terminal driver ioctls.  Both drivers utilize the
>            ``line  discipline''  notion,  allowing dynamic choice among
>            several protocols by the user process.
>
>                 Berkeley offers several new features in  4.1C BSD  over
>            the V7 terminal driver.  Some of these are accessed as a new
>            line discipline (the ``new tty'' discipline),  while  a  few
>            others  are implemented as additional ioctl calls.

Thanks,

/Mary Ann Horton/ (she/her/ma'am)
       Award Winning Author
maryannhorton.com <https://maryannhorton.com>



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