Atomic file-sustitution in .NET?

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Helge Jensen - 07 Sep 2005 09:30 GMT

On unix-based systems i use (the libc function) "rename" to do atomic
replacement of one file with another.

How would I achieve the same using .NET primitives?

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Oliver Sturm - 07 Sep 2005 10:09 GMT

>On unix-based systems i use (the libc function) "rename" to do atomic
>replacement of one file with another.
>
>How would I achieve the same using .NET primitives?

There are two Windows API functions that might be useful: ReplaceFile and
MoveFileEx. Both seem to be able to replace a file if used with the
correct parameters, but none of them guarantee atomicity. I don't think
any of them is available via .NET framework classes.

I googled for "windows posix rename" and I came up with a few mailing list
threads discussing the issue, with the general consent being that Windows
can't do it - many things in Windows file handling aren't very POSIX
compatible, after all.

Oliver Sturm

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Helge Jensen - 07 Sep 2005 11:13 GMT

> I googled for "windows posix rename" and I came up with a few mailing
> list threads discussing the issue, with the general consent being that
> Windows can't do it - many things in Windows file handling aren't very

Unfortunatly , this is what I suspected :(

> POSIX compatible, after all.

I'm not really too interested in whether the behaviour is POSIX, but in
mechanisms to guarantee consistency during updates. I guess ill have to
live with the race-condition and data-loss possibility of the pattern:

if ( File.Exists(path) )
File.Remove(path);
File.Move(path, newpath);

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Oliver Sturm - 07 Sep 2005 11:36 GMT

>I'm not really too interested in whether the behaviour is POSIX, but in
>mechanisms to guarantee consistency during updates. I guess ill have to
[quoted text clipped - 3 lines]
> File.Remove(path);
> File.Move(path, newpath);

There's no way around that pattern, I think. But it should read:

if ( File.Exists(newpath) )
File.Remove(newpath);
File.Move(path, newpath);

Oliver Sturm

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Helge Jensen - 07 Sep 2005 11:43 GMT

> There's no way around that pattern, I think. But it should read:
>
> if ( File.Exists(newpath) )
> File.Remove(newpath);
> File.Move(path, newpath);

Thanks, for pointing out my typo ;)

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Atomic file-sustitution in .NET?

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