gordon@prls.UUCP (Gordon Vickers) (04/28/89)
[ REPOST for wider distribution ( /ca/usa/ ) ]
How do I get exclusive use of a shared (/etc/ttys) tty line ?
I am writing a program to be exicuted from crontab that will switch
my modem to auto-answer at night, and back to originate only in the
mornings. I am not interested in using a shell script that will edit
/etc/ttys becouse my goal is to dissable the modem from going off hook
to answer calls that are intended for me personnally (voice).
The modem's tty port is a shared (/etc/ttys) line.
My program will currently do what it is required to do but each time
the modem sends something back ("OK"), the login-in prompt is getting
sent to the modem.
I've tried opening the port with:
int modem;
modem = open(dev,O_RDWR | O_BLKANDSET)
but open returns NULL and I don't understand what that is suppose to
mean. Seems like it should mean that "the open completed without error
but your not getting a file discriptor".
I did not expect the open to return until my process had set the
TIOCSINUSE bit (ioctl).
When I tried looping on the open while it returns NULL, the process
stays in the loop forever.
How do I tell the system that I want this port exclusively and I'm willing
to wait for it ?
I'm running Ultrix 3.0 on a VAX 11/750. The modem port is port 1 of a
DMF-32 .
Thank you,
Gordon Vickers 408/991-5370 (Sunnyvale,Ca); {mips|pyramid|philabs}!prls!gordon
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