Re: [Mingw-users] Removing the same file from two consoles

[Benjamin R. <Ben...@ep...>]

Hi Alex,


"Alex Vinokur" <al...@co...> writes:
> Here is some program which was invocated on two consoles.
>
> The program behavior is different on
>  * Cygwin, DJGPP on the one hand
>    and
>  * Mingw on the other hand
>  environments.

If I understand you correctly, you see that with MS's runtime (Mingw)
a file that is open can not be removed, while with the Cygwin runtime
it can.

> Which is right/correct/preferable?

Both are "right" or "correct".  The standard C runtime specification
doesn't prescribe any file locking issues, which is what you see here.
So this depends on the actual implementation of fopen().


MS is coming from DOS, a single-process system.  When they introduced
Windows, they have decided to opt for system integrity and disallow
access to files while they are open in another process.  That way a
program that worked in the single-process DOS system, will continue to
work in the multi-process Windows system without needing additional
protection.  For compatibility this implementation has never changed.

If you want to use more low-level functions than fopen(), there are
APIs for sharing and locking in Windows, to control the sharing of
files even while they are open.

Note that Mac OS does/did the same thing, up until the introduction of
a Unix basis for their OS in Mac OS X.


Cygwin OTOH is coming from Unix, which always was a multi-process
system and which traditionally doesn't have *any* file locking in
place by default.  Unix programs are supposed to know that and if they
want to share files, they have to implement or use some extra locking
scheme.  If you want to protect the files of a server process, you can
run the process under its own user account and assign its files to
that user account.


benny