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Path: utzoo!mnetor!uunet!seismo!mimsy!oddjob!gargoyle!ihnp4!cuae2!killer!jfh
From: jfh@killer.UUCP (The Beach Bum)
Newsgroups: comp.bugs.sys5
Subject: Re: CLOCAL, or catch-22
Message-ID: <1302@killer.UUCP>
Date: Fri, 7-Aug-87 17:03:31 EDT
Article-I.D.: killer.1302
Posted: Fri Aug  7 17:03:31 1987
Date-Received: Wed, 12-Aug-87 07:18:09 EDT
References: <325@nsta.UUCP>
Organization: Big "D" Home for Wayward Hackers
Lines: 29
Summary: try using O_NDELAY

In article <325@nsta.UUCP>, amos@nsta.UUCP writes:
> One of the optional flags of the c_cflag field of termio is CLOCAL. (see
> <termio.h>)  It is  supposed  to  cause the  tty  driver  to ignore  the
> 'carrier detect' bit  in the RS232 interface, and open  the line anyway.
> 
> However, the  only way to set  this flag is  by a ioctl call;  the ioctl
> call needs  a file-descriptor  argument; a  file-descriptor can  only be
> obtained by a successfull open call...

there is a flag (least ways in system V there is a flag ...)
in fcntl.h named O_NDELAY that causes the open to not wait,
and if i remember the documentation correctly, one of the
uses given is opening a port that doesn't have DSR or DCD
asserted yet.

i have used this approach on our p/60 and p/95, and it works
on them.  as they say, "your mileage may vary ..."

also, i seem to remember that some of the cu(1)'s i've seen
have a no-wait flag (i recall it is used for dialing out on
modems since DCD wouldn't have been asserted yet.  might
want to try that approach.

- john.
-- 
John F. Haugh II		HECI Exploration Co. Inc.
UUCP:	...!ihnp4!killer!jfh	11910 Greenville Ave, Suite 600
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