Turning FNDELAY *off*

[Barton E. Schaefer]

In article <4180 at ogccse.ogc.edu> I wrote:
} Surely there must be an obvious way to do this, and I'm just missing it.
} 
}     if (fcntl(sd, F_SETFL, FNDELAY) < 0) {
} 	perror("fcntl");
} 	exit(1);
}     }
} 
} Is there any way to restore blocking read/write on a descriptor?

As expected, I was indeed missing the obvious.  The following people all
pointed it out in basically the same way, with various degrees of "Hint!
Hint!" :-) commentary leading up to the actual solution:

	Chris Torek <chris at mimsy.umd.edu>
	loverso at Xylogics.COM (John Robert LoVerso)
	guy at auspex.com (Guy Harris)

The answer is that, as I should have realized, fcntl() works just like
ioctl(), and with F_SETFL it sets/clears whatever bits are on/off in the
third parameter.  So for my particular problem, it suffices to do

    if (fcntl(ad, F_SETFL, 0) < 0) {
	perror("fcntl");
    }

and, in the more general case,

    if ((flags = fcntl(ad, F_GETFL, 0)) < 0) {
	perror("fcntl: can't get flags:");
    }
    else if (fcntl(ad, F_SETFL, flags & ~FNDELAY) < 0) {
	perror("fcntl: can't set flags:");
    }

I got a different answer from Phil Hochstetler at Sequent, for you other
DYNIX users.  I haven't tried this one, because the fcntl() solution
works fine.

} From: sequent!phil (Phil Hochstetler)
} 
} I believe the proper way to do this is:
} 
} 	int	on = 1,
} 		off = 0;
} 
} 	/* turn on non blocking I/O on a socket */
} 	if (ioctl(fd, FIONBIO, &on) < 0) {
} 		perror("ioctl");
} 		exit(1);
} 	}
} 
} 	/* turn off non blocking I/O on a socket */
} 	if (ioctl(fd, FIONBIO, &off) < 0) {
} 		perror("ioctl");
} 		exit(1);
} 	}
} 
} I think the problem is a basic BSD one .. 4.X BSD never did this
} the way the doc states (or used to do it both ways).  Give the above
} a try.
} -- 
} Phil Hochstetler		UUCP:  uunet!sequent!phil

Thanks to everyone who responded.
-- 
Bart Schaefer           "And if you believe that, you'll believe anything."
                                                            -- DangerMouse
CSNET / Internet                schaefer at cse.ogc.edu
UUCP                            ...{sequent,tektronix,verdix}!ogccse!schaefer