Path: utzoo!mnetor!tmsoft!torsqnt!hybrid!scifi!bywater!uunet!rbj
From: rbj@uunet.UU.NET (Root Boy Jim)
Newsgroups: comp.unix.wizards
Subject: Re: Unblocking filedescriptor(s)
Keywords: fcntl,ioctl
Message-ID: <120184@uunet.UU.NET>
Date: 27 Jan 91 06:25:43 GMT
References: <1991Jan25.235221.21868@odin.diku.dk>
Organization: UUNET Communications Services, Falls Church, VA
Lines: 22

In article <1991Jan25.235221.21868@odin.diku.dk> cthulhu@freja.diku.dk (Stefan Krabbe) writes:
>I am programming in a 4.3BSD environment...
> In a program I am currently writing I make a filedescriptor unblocking
>this way:
>             fcntl(filedescriptor, F_SETFL, FNDELAY);

What you really want to do to make it unblocking is something like:

	flags = fcntl(fd, F_GETFL, 0);		/* get old flags */
	flags |= FNDELAY;			/* add no delay */
	fcntl(fd, F_SETFL, flags);		/* set new flags */

Your code sets the flags to FNDELAY, and clears any existing flags.
My code adds FNDELAY to the existing flag set.
	
> But what do I do if I want it make it blocking again? 

I think you can take it from here.
-- 

	Root Boy Jim Cottrell <rbj@uunet.uu.net>
	Close the gap of the dark year in between