[Rd] File lock mechanisms in R
Prof Brian Ripley
ripley at stats.ox.ac.uk
Tue Jul 3 10:29:03 CEST 2007
On Mon, 2 Jul 2007, Henrik Bengtsson wrote:
> 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.
> R-devel at r-project.org mailing list
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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