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How is deny mode implemented in UNIX?


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Hello all!

In order to not jeopardize concurrent access to a file, I have made some tests with the "deny mode" wire to the "open file" vi. It seems to work (I am using lv 7.1.1 on Solaris). I do accesses from different hosts that map the same NFS partitions. Looking at the file properties during execution of the tests, no permissions are altered. Neither can I see that any kind of lock file is created. I have also noticed the the file is only locked for labview. I can access the file perfectly with emacs or cat.

My question is therefore: How is this "deny mode" functionality implemented in solaris? I dont want to break it unintentionally.

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QUOTE (Jon Sjöstedt @ Sep 3 2008, 03:39 AM)

Hello all!

In order to not jeopardize concurrent access to a file, I have made some tests with the "deny mode" wire to the "open file" vi. It seems to work (I am using lv 7.1.1 on Solaris). I do accesses from different hosts that map the same NFS partitions. Looking at the file properties during execution of the tests, no permissions are altered. Neither can I see that any kind of lock file is created. I have also noticed the the file is only locked for labview. I can access the file perfectly with emacs or cat.

My question is therefore: How is this "deny mode" functionality implemented in solaris? I dont want to break it unintentionally.

Not sure about Solaris really and Solaris in many ways is often a bit special. But on Linux it seems to be implemented by range locking the entire file.

fcntl(fd, F_SETLK, &lock)

Rolf Kalbermatter

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