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Concurrent writes to the same file

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  Concurrent writes to the same file Jason Friedman <jsf80238@gmail.com> - 2013-07-10 22:57 -0600
    Re: Concurrent writes to the same file Nobody <nobody@nowhere.com> - 2013-07-11 09:30 +0100

#50413 — Concurrent writes to the same file

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Other than using a database, what are my options for allowing two processes
to edit the same file at the same time?  When I say same time, I can accept
delays.  I considered lock files, but I cannot conceive of how I avoid race
conditions.

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#50428

On Wed, 10 Jul 2013 22:57:09 -0600, Jason Friedman wrote:

> Other than using a database, what are my options for allowing two processes
> to edit the same file at the same time?  When I say same time, I can accept
> delays.

What do you mean by "edit"? Overwriting bytes and appending bytes are
simple enough, but inserting or deleting bytes such that subsequent bytes
change their offsets is harder.

> I considered lock files,

Well, you shouldn't have, unless you're targeting a platform which doesn't
support file locks (are there any left?).

> but I cannot conceive of how I avoid race conditions.

By using locks. E.g. fcntl.lockf() or msvcrt.locking().

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