[Info-vax] DECnet Phase IV broken after VSI update

[Lawrence D’Oliveiro]

On Friday, November 5, 2021 at 3:14:06 AM UTC+13, osuv... at gmail.com wrote:
>
> On Thursday, November 4, 2021 at 9:23:38 AM UTC-4, Arne Vajhøj wrote: 
>>
>> Sounds like somebody did not like SYS$QIO(W).
>
> Considering how slow the VAX was and that terminal I/O was often many 
> many small transfers, that kind of micro-optimization was probably worth 
> while.

Remember the old saying, variously attributed to Hoare or Knuth: “premature optimization is the root of all evil”. By making pseudo-terminals a special case, they lost the ability to treat it uniformly as part of a common event loop I/O framework.

Meanwhile, Unix systems had the pty(7) device. Open one, and you get just another file descriptor, and you access it with normal read(2) and write(2) calls, same as any other file descriptor. And you can use it with select/poll/epoll.