dial-out/terminal program for Ultrix 4.x

[Guy Helmer]

In <1991May18.171343.24595 at decuac.dec.com> mjr at hussar.dco.dec.com (Marcus J. Ranum) writes:

>ltf at ncmicro.lonestar.org (Lance Franklin) writes:

>>Alternately, has anybody had any better luck porting pcomm, xcomm or ECU
>>to Ultrix?  In particular, how does one keep getty or uucp from grabbing
>>the tty port while you're using it?

>	Locks on modems are traditionally done by placing a lock file
>with the device name in /usr/spool/uucp, named LCK..dev, so a lock for
>a modem hooked up to /dev/ttyd1 would be LCK..ttyd1

>From my examination of the Ultrix open(2) call and
recent work with bringing up ckermit on Ultrix, it seems that the kernel
offers support for locking above and beyond the simple lock file scheme.
This kernel support has to be used in a communications program that
plans to share a line with the stock Ultrix getty, uucico, and tip
programs.  See the O_BLKANDSET and O_BLKINUSE flags for open(2) (which
can be used with O_NONBLOCK, so the open(2) call won't block if the
desired file is in use).
-- 
Guy Helmer, Dakota State University Computing Services
helmer at sdnet.bitnet, dsuvax!ghelmer at wunoc.wustl.edu, ghelmer at dsuvax.dsu.edu
"Everybody need a soft filter / Everybody need reverse polarity" - Rush