Looking for general advice on complex program

Cameron Simpson cs at zip.com.au
Fri Jul 15 18:37:41 EDT 2011

On 15Jul2011 16:03, Billy Mays <81282ed9a88799d21e77957df2d84bd6514d9af6 at myhashismyemail.com> wrote:
| I remember reading that file locking doesn't work on network mounted
| drives (specifically nfs mounts), but you might be able to simply
| create a 'lock' (mydoc.xml.lock or the like) file for the XML doc in
| question.  If that file exists you could either hang or silently
| give up.  Not sure if that helps.

There are two approaches to this. Plain old make-a-file won't work - it
is racy (and as mentioned, you can't rely on the various lock

You can create a file while your umask is 0777; it will be non-writable
immediately (no chmod required), preventing another attempt to make it.

My personal habit is to make a directory for the lock; mkdir
also can't happen twice to the same name, you don't need to fiddle you
umask (racy and annoying, and problematic if you're using multiple
threads), _and_ you can put meta info inside it, like pid files etc.

Cameron Simpson <cs at zip.com.au> DoD#743

I had a wierd dream with Ken Thompson in it once.
        - George Politis <george at research.canon.com.au>

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