Path: utzoo!censor!geac!torsqnt!jarvis.csri.toronto.edu!cs.utexas.edu!rice!sun-spots-request
From: auspex!guy@uunet.uu.net (Guy Harris)
Newsgroups: comp.sys.sun
Subject: Re: Lock Daemon, lockf fails
Keywords: SunOS
Message-ID: <5291@brazos.Rice.edu>
Date: 22 Feb 90 19:41:06 GMT
Sender: root@rice.edu
Organization: Sun-Spots
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Approved: Sun-Spots@rice.edu
X-Refs:  Original: v9n16, Replies: v9n36
X-Sun-Spots-Digest: Volume 9, Issue 53, message 8

>4. It's worth pointing out a SunOS fcntl locking "feature" that may not be
>obvious: if you open() 2 file descriptors on a single file, fd1 and fd2,
>establish a lock on fd1 and then close(fd2), the lock established through
>fd1 is lost.

That's not a "SunOS fcntl locking feature", it's a System V "fcntl"
locking feature.  To quote SVID Issue 2, volume 3, FCNTL(BA_OS):

	...All locks associated with a file for a given process are
	removed when a file descriptor for that file is closed by that
	process or the process holding that file descriptor terminates.

Note that it says "a file descriptor", not "the file descriptor with which
that lock was established" or something like that.

In addition, note that POSIX says the same thing; in other words, it's not
specific to SunOS, and you'd better be prepared for it to work that way on
*all* UNIX systems (and even non-UNIX POSIX systems).