Re: [Rd] File lock mechanisms in R

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Tue, 03 Jul 2007 09:29:03 +0100 (BST)

On Mon, 2 Jul 2007, Henrik Bengtsson wrote:

> Hi,
>
> is there a (cross-platform) file-locking mechanism available in R (or
> via some package)?

I don't believe there really is a cross-platform file-locking mechanism available to any language. File-locking is an OS feature, and the semantics differ. For those unfamiliar with this, the Wikipedia article is a good start (but ignores the POSIX lockf interface).

> I am looking for a way to have one R session lock a file for
> read/write access, while being updated/modified by another R session.
> This will provide me with a-poor-mans parallelization method. It is
> ok to have so called advisory looking (as in Unix), which are
> non-mandatory to follow. If not available, I'll use lock files, but
> there are some potential problems in creating such in an atomic way.

Depends what you mean by 'atomic'. In R, the only way to have non-interruptible operations is via .Call or similar: the evaluator is interruptible at all times so it seems that this issue applies equally to all file locking from R.

> Ideally I wish to have this working on all platforms.
>
> Cheers
>
> Henrik
>
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>
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-- 
Brian D. Ripley,                  ripley_at_stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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