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Postings from August 2010
Quoth avar@cpan.org: > On Mon, Aug 9, 2010 at 23:05, Jan Dubois <jand@activestate.com> wrote: > > > > The problem is that the monkeypatch is documented (in README.cygwin), so > > just removing it doesn't feel quite right either. Ideally someone would > > go in and update the patch to remove the backup file when it is being > > closed. Then this patch could be enabled for other DOSISH platforms too > > (maybe with a somewhat more obscure extension than .bak to avoid > > conflicts with existing filenames). > > If we're set on adding perl -pi emulation on Windows it would probably > be best just to create a backup file with the equivalent of > File::Temp, and unlink it when we're done with it. IMHO -i on all platforms should open ARGVOUT to a tmpfile, and rename(2) it over the original when it's done. This is a reversal of the usual behaviour of -i, but it's enormously safer. (It's really annoying there isn't a flink(2) syscall, which would let you unlink the tempfile right away and then link it in place atomically at the end.) > The only problem with that is that perl might run out of diskspace > when doing -pi on large files, This is no different from the situation on Unix. -i with no backup unlinks the original file, but the disk space (obviously) isn't freed until the filehandle is closed. -i in all cases requires enough space for both old and new files to exist simultaneously. > or slowly accumulate garbage if it's > e.g. being killed before it gets around to the unlink(). IIRC the equivalent of Unix' close-behind on Win32 is a flag that will cause the OS to delete the file when it gets closed. That sounds exactly right for this situation (better, in fact, than close-behind, since the file needs a name to get renamed). The flag would have to be cleared just before renaming, of course, which still leaves a small race condition. (Taking a quick look at MSDN, it seems to me that -i should in any case be using ReplaceFile, which handles making a backup while also preserving the attributes of the replaced file.) BenThread Previous | Thread Next