NFS File Locking 2007-11-28 - By Karl Pearson
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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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> - Rick Stevens, Principal Engineer rstevens@(protected) -
> - CDN Systems, Internap, Inc. http://www.internap.com -
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> - Have you noticed that "human readable" configuration file -
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--
Karl L. Pearson
karlp@(protected)
http://consulting.ourldsfamily.com
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