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Re: login(1) vs "dialout ttys"



Dennis Ferguson <dennis.c.ferguson%gmail.com@localhost> writes:

> No, /dev/ttydX apparently just meant "attached to a modem" (we didn't do
> this).  Through 4.3 BSD at least the BSD terminal driver did not have a
> separate device for dial out.  If you wanted to use a modem for dial out
> you would open the same device file as was used for dial in, but with a
> O_NONBLOCK flag given to open() followed by some other magic (my memory is
> dim) that was supposed to lock out pending opens waiting for carrier.  This
> was very buggy and full of race conditions, so we avoided trying to share
> modems for both dial-in and dial-out use.  The /dev/dtyXX thing may have
> come from System V (or the System V-based SunOS) and was supposed to fix
> the races.

Thanks for the explanation  of /dev/ttydX.  I remember using the
dtyXX/ttyXX dual minor devices, for dialout/dialin, and it did work
reliably.   That might have been on 2.11BSD, or it may have been more
recent.

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