open files

Jim Salter jim at
Fri Feb 20 23:06:17 GMT 2004

Hmmm.  It's odd to think that Cygwin always uses backup semantics, 
because it DEFINITELY fails to process quite a lot of files that the 
high-dollar win32-native backup utilities can process.

My experience has been that cygwin can open (for reading) any file that 
you can use the GUI to drag-and-drop-copy, but it cannot open any file 
that the GUI will not drag-and-drop copy.

Example: you're downloading a large MPEG using IE.  WMP will refuse to 
open the partial file because it's locked to some extent - but you can 
use the GUI to make a copy of the partial file, and WMP will then open 
the copy.

Some other files, however - for instance Outlook .PST files - are 
absolutely uncopyable using the GUI when they are locked by the 
processes that play with them.

My experience is that cygwin can open files that are locked read-only - 
like partial IE downloads - but CANNOT open files that are completely 
locked - like Outlook's .PSTs.

Please keep us posted how your research on this stuff turns out.


 > I've received a reply from the Cygwin people that suggests
 > Cygwin _always_ uses backup semantics, and a little information
 > about how.  It's some pretty hairy code and I'm still deciphering
 > it, but it could be that I was authoring that patch for nothing.
 > I'll post more when I figure it out.

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