Re: serial callout devices

Keith Owens (kaos@ocs.com.au)
Tue, 01 Jun 1999 10:10:37 +1000


On Mon, 31 May 1999 16:43:16 -0500 (EST),
"Alan Curry" <pacman-kernel@cqc.com> wrote:
> (
> stty 38400
>
> chat -f /usr/lib/ppp/chatscript
> case $? in
> 0) echo "Success" 1>&2
> /usr/sbin/pppd & ;;
> 4) echo "BUSY" 1>&2 ;;
> *) echo "call failed" 1>&2 ;;
> esac
> ) </dev/modem >/dev/modem

The problem with that script or any method that uses shell redirection
is that the shell tries to open /dev/modem without the O_NONBLOCK flag.
On /dev/cua* it usually works, on /dev/ttyS* it often hangs waiting for
the device to open. Remember that the shell tries to open redirectoed
files before it runs the script, without shell support for O_NONBLOCK
it is doomed to failure on /dev/ttyS*.

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