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From: mikel@teda.UUCP (Mikel Lechner)
Newsgroups: comp.unix.wizards
Subject: Re: NFS question
Message-ID: <304@teda.UUCP>
Date: 6 Feb 90 22:54:39 GMT
References: <22351@adm.BRL.MIL>
Organization: Teradyne EDA Inc., Santa Clara, Calif.
Lines: 32

richard@pemrac.space.swri.edu (Richard Murphy) writes:

>I have two machines, A & B that share a file system via NFS. The file
>system is exported from A and mounted by B. On machine B I start a
>process to display the last line written to a file that is on this
>file system. On machine A I start a program to write to this same file.
>What happens is this: if the file has non-zero length when the display
>program opens it, all goes well. However, it is initially empty, the
>display program never sees anything that the writing program puts into
>it. Why does this happen? Since NFS is stateless, should not prior
>knowledge of the length of the file be discarded at some point?

From what you've described, it sounds like a bug in your NFS implementation.
It would help if you would give more details about what type of system
you are running and the  revision level of the software.

I had a similar problem with SunOS4.0 about a year ago.  In some circumstances
when data was written to a file that was being accessed via NFS, the
new data was not seen by other systems unless the file was closed and reopened.
We didn't do this kind of thing often, so we worked around the problem.
I noticed that when we installed SunOS4.0.3 that the problem went away.
I figured it was some bug in the NFS cacheing scheme.  There were a lot
of changes that went into the SunOS4.0 release, so it was quite buggy
until it was replaced by 4.0.1.

If you are running Suns, I would recommend upgrading to SunOS4.0.3.

-- 
				If you explain so clearly that nobody
				can misunderstand, somebody will.
Mikel Lechner
Teradyne EDA, Inc.		UUCP:  mikel@teraida.UUCP