Yeah it should work supposedly but its not working. For reference I'm attaching a sample file may be I am doing something very wrong. I make executable of attached code. Then run one instance on terminal & 2nd on another terminal. Executable on 2nd terminal is able to write in the file. Regards, ~Nishant <div class="gmail_quote">On Sat, Nov 22, 2008 at 12:56 AM, Mark Haney <<a href="mailto:mhaney@ercbroadband.org">mhaney@ercbroadband.org</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="Ih2E3d">test test wrote: > Hello, > > > > I need to put a mandatory lock on /dev/fb0 (presently any file) in Linux OS. > But in actual scenario it will be a device file. > > > > OS: Ubuntu Hardy Heron 8.04 > > > > Scenario: > > 1. Process A is super process (controller). > > 2. Process B is normal process. > > 3. *Process A and B are non-cooperating process, they simple don't know > about other process existence and they are not interested in knowing it > either.(So, advisory locking is out of scope). * > > 4. At particular instance Process B is accessing /dev/fb0. > > 5. Now, Process A wants access to it. > > 6. Process A locks /dev/fb0 > > 7. It can hold the lock as long it wants & in any case process B cannot > write anything to it. (It's better if B cannot read the contents also). > > > > I also changed permissions of directory and lock file. > > > > I used: > > chmod g-x test > > chmod g+s test > > </div><a href="http://www.hackinglinuxexposed.com/articles/20030623.html" target="_blank">http://www.hackinglinuxexposed.com/articles/20030623.html</a> That was a quick google on file locking in Linux. Are you coding these processes yourself? I mean there are documented ways of locking files programmatically in linux as well. Based on what you posted the file locking should work. Are you saying it doesn't? -- Frustra laborant quotquot se calculationibus fatigant pro inventione quadraturae circuli Mark Haney Sr. Systems Administrator ERC Broadband (828) 350-2415 Call (866) ERC-7110 for after hours support -- ubuntu-users mailing list <a href="mailto:ubuntu-users@lists.ubuntu.com">ubuntu-users@lists.ubuntu.com</a> Modify settings or unsubscribe at: <a href="https://lists.ubuntu.com/mailman/listinfo/ubuntu-users" target="_blank">https://lists.ubuntu.com/mailman/listinfo/ubuntu-users</a> </blockquote></div>