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From: kline@CS.Arizona.EDU (Nick Kline)
Newsgroups: comp.sys.next.programmer,comp.unix.bsd
Subject: detecting carrier for ttyfa
Followup-To: comp.sys.next.programmer
Date: 18 Jul 1993 03:28:39 -0700
Organization: University of Arizona CS Department, Tucson AZ
Lines: 36
Message-ID: <22b8ko$a7j@cheltenham.cs.arizona.edu>
NNTP-Posting-Host: cheltenham.cs.arizona.edu
I can't reliably detect whether the carrier is on when I am using
/dev/ttyfa.
I use the call:
int carrier(int ttyNum)
{
int result;
if(ioctl(ttyNum,TIOCMGET,&result) < 0) {
printf("bad ioctl\n");
return 0;
}
else {
printf("result is %x\n",result);
return result & TIOCM_CD;
}
}
when the carrier is on, the bit for 64 should be set. it is usually, but
not always. when the carrier is not on, it usually, but not always says
that this bit is off.
any suggestions which this wouldn't work?
if I haven't used the modem lately, and i call someplace, then the carrier
is initially correctly shown to be off. then if i call some place, the
carrier is usually correctly shown on. if i log out, and then test the
carrier bit again, it says it's still on.
Is there something that needs to be done to 'flush' the state, other than
redoing the ioctl?
-nick