NFS File Locking

[Karl Pearson]

On Wed, November 28, 2007 7:26 pm, Rick Stevens wrote:
> On Wed, 2007-11-28 at 18:19 -0700, Karl Pearson wrote:
>> On Wed, November 28, 2007 12:08 pm, Rick Stevens wrote:
>> > On Wed, 2007-11-28 at 09:27 -0800, Waldher, Travis R wrote:
>> >> Is there a command I can use to manually lock a file?
>> >>
>> >>
>> >>
>> >> My goal is to test NFS file locking with groups greater than 16.
>> >
>> > I don't know of one, but it wouldn't be hard to write.  You'd need to
>> > open the file, lock it via fcntl() (flock() does not work over NFS) and
>> > hold the lock until not needed.
>> >
>> > Remember that if the program exits, the lock would be released.
>>
>> Can't you just emacs or vi the file and accomplish the same thing? Just a
>> thought to save something or other.
>
> I'm not 100% sure of that.  Typically an editor doesn't take a write
> lock on a file.  Rather, the editor makes a work copy of the file which
> you edit (which is why editing a large file in vi takes so long to
> start...it's making a copy of the file).  Some editors actually just
> keep a record of what you did.  If you "quit and discard changes", the
> work file or the log of what you did are simply discarded and the
> original file is left alone.
>
> When you "exit and save", the old file gets overwritten by the work file
> or the edits get played back to modify the file.  So, the only time a
> write lock is made on the file is when you commit the edits.

I believe you. So, what of something like XV or GIMP then? They make an
exclusive lock against the file, don't they?

Karl

>
> ----------------------------------------------------------------------
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-- 
Karl L. Pearson
karlp at ourldsfamily.com
http://consulting.ourldsfamily.com
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