Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!mcvax!ukc!stc!root44!njh From: njh@root.co.uk (Nigel Horne) Newsgroups: comp.bugs.sys5 Subject: Re: CLOCAL, or catch-22 Message-ID: <394@root44.co.uk> Date: Mon, 10-Aug-87 05:56:53 EDT Article-I.D.: root44.394 Posted: Mon Aug 10 05:56:53 1987 Date-Received: Wed, 12-Aug-87 05:01:34 EDT References: <325@nsta.UUCP> Reply-To: njh@root44.UUCP (Nigel Horne) Distribution: world Organization: Root Computers Ltd, London, England Lines: 26 In article <325@nsta.UUCP> amos%nsta@nsc.com (Amos Shapir) writes: > One of the optional flags of the c_cflag field of termio is CLOCAL. (see > ) It is supposed to cause the tty driver to ignore the > 'carrier detect' bit in the RS232 interface, and open the line anyway. > This is needed for ports that do not have the DC wired; trying to open > such a port without setting the CLOCAL bit first, will cause the open to > hang forever waiting for a carrier signal. > > 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... > > The only solution if you don't have sources is to re-wire all your > terminal plugs by shorting CD to DTR or something like that. In fact what you do is to open the tty line with O_NDELAY set. e.g. open ("/dev/ttya", O_RDWR | O_NDELAY); -Nigel -- -- Nigel Horne, Divisional Director, Root Technical Systems. G1ITH Fax: (01) 726 8158 Phone: +44 1 606 7799 Telex: 885995 ROOT G BT Gold: CQQ173