On Tue, Jun 14, 2022 at 04:32:21PM +0100, Sam Edge wrote: > On 14/06/2022 12:25, Adam Dinwoodie wrote: > > Microsoft OneDrive has a "Files On-Demand" function, where it will > > synchronise file metadata to a local system, but won't actually download > > the file content until an application attempts to read the content. > > When moving a file within Cygwin using `mv`, the file always gets > > downloaded, which seems like it shouldn't be necessary. Is there any > > way to have `mv` (and presumably the underlying rename call) work > > without downloading the file content in this circumstance? It'd > > definitely make some of my life easier, but I'm not sure if it's a > > trivial issue, one that would require years of work, or somwhere in > > between... > > > > As best I can tell, `mv` doesn't need to know the content of the file, > > at least as long as it's not moving the file outside of OneDrive; it > > feels very similar to me to moving a file within a partition on *nix: > > generally it's just a case of updating the directory records, with no > > need to look at the file content. > > > > This does work as desired from within PowerShell: PowerShell's > > `Move-Item` won't download a file that's not currently stored on the > > local system. So it's presumably possible to achieve this, although I > > don't know if it'd rely on non-public Microsoft APIs, and/or lots more > > complexity in the Cygwin code. > > > > Simple demonstration below, showing the different behaviours of > > PowerShell versus Cygwin. I've not included a cygcheck.out, as I'm > > pretty sure this is much closer to a feature request than a problem > > report, but let me know if I've got that wrong. > > Greetings Adam. > > I wasn't even aware you could do that with OneDrive - there's still no > Explorer > way of doing it in Windows 10 21H2 as far as I can see. Thanks for the > info. :-)
FWIW, this also works exactly the same using click-and-drag or Ctrl+C / Ctrl+V in File Explorer for me, on all my Windows systems (currently running a mix of Win11 Enterprise and Win11 Pro, both the 22H2 releases), and I *think* I remember it working on Win10 too, but I'm less confident there. > I imagine Cygwin doesn't know about the extended attributes being used > within > the local copy of your OneDrive directory so it is doing the move using the > underlying POSIX 'rename within mount' API which hopefully uses the Win32 > 'rename' but not in a way that carries the new 'O' attribute. That seems very plausible; I know Cygwin's mv/rename seems to keep at least some of the Windows file attributes, but I definitely don't profess any expertise here. > Presumably PowerShell's Move-Item does use the right flags to the Win32 API > call. > > One of the problems the Cygwin maintainers have is that Microsoft introduces > 'enhancements' to NTFS & the Win32 API arbitrarily in Windows updates > without > announcing them so it's a game of whack'a'mole. Yeah, I am painfully familiar with that sort of problem from Microsoft, not just with Windows! -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
