copy /uf and usb key

[David Marcus]

I don't understand what is happening with copy /uf. My c: drive is an ntfs hard disk. My f: drive is a FAT USB key. I copy a file from c: to f:, then copy /uf it back. I would expect that it wouldn't be copied back, but it is.

C:\Junk>echo %@filetime[Foo.bar,,s] %@fileage[foo.bar]
20:37:39 129745030598204083
 
C:\Junk>copy Foo.bar f:\
C:\Junk\Foo.bar => F:\Foo.bar
    1 file copied
 
C:\Junk>echo %@filetime[f:\Foo.bar,,s] %@fileage[f:\foo.bar]
20:37:40 129745030600000000
 
C:\Junk>copy /uf f:\Foo.bar .
F:\Foo.bar => C:\Junk\Foo.bar
    1 file copied
 
C:\Junk>echo %@filetime[Foo.bar,,s] %@fileage[foo.bar]
20:37:40 129745030600000000
 
C:\Junk>ver

TCC  13.03.45   Windows Vista [Version 6.0.6002]

 

[Charles Dye]

FAT only has a granularity of two seconds for file update times, whereas NTFS file times are much more accurate (sub-millisecond), therefore you will nearly always get the 'wrong' result in one direction or the other when doing a /u copy from FAT to NTFS or vice versa

Hence the /UF.

It looks to me like, when Windows copies from NTFS to FAT, the file time gets rounded to the nearest two-second interval, not truncated as I would expect.

 

[Steve Pitts]

Hence the /UF

I was too quick off the mark Charles, modified my post twice (adding references to the UF and age resolution) and then decided that it was all utter tosh and removed it :)

 

[David Marcus]

Rounding shouldn't matter, since the rounded value should still be less than two seconds from the original value. I can duplicate the problem on Vista and Windows 7 and two different USB keys.

 

[David Marcus]

Is this a bug?

 

[rconn]

Is this a bug?

Works here with 13.03.49.