[Haskell-beginners] Re: how to read file with locking

[Ertugrul Soeylemez]

Joey Hess <joey at kitenet.net> wrote:

> Ertugrul Soeylemez wrote:
> >   readFileLocked :: FilePath -> IO B.ByteString
> >   readFileLocked fn =
> >     withFile fn ReadMode $ \h -> do
> >       lockFile h  -- for a suitable function lockFile
> >       B.hGetContents h
> >
> > It is, BTW, always preferable to use withFile over openFile, if you
> > can.  This makes your code cleaner and also exception-safe.
>
> Unless there is a better locking primative than waitToSetLock
> available, I don't know how to build your lockFile function. It seems
> that it would have a side effect of closing the handle. It could
> return a new handle like this, but then withFile's automatic close of
> the file would be defeated.

I wasn't addressing the locking issue, but rather the laziness issue.
The lockFile function was just a placeholder.


Greets,
Ertugrul


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