file timestamp and Windows 7

momo33 has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: file timestamp and Windows 7 by mjscott2702 (Pilgrim) on Jan 05, 2011 at 08:59 UTC
On a Windows 7 machine with NTFS, modification time was successfully updated using: Cygwin `$ ls -goc dummy.txt; perl -e 'utime undef, undef, "dummy.txt"'; ls -go +c dummy.txt -rw-r--r--+ 1 0 2011-01-05 08:44 dummy.txt -rw-r--r--+ 1 0 2011-01-05 08:49 dummy.txt` [download] and ActiveState perl: `>dir dummy.txt 05/01/2011 08:49 0 dummy.txt >perl -e "utime undef, undef, 'dummy.txt'" >dir dummy.txt 05/01/2011 08:53 0 dummy.txt` [download] I think the file system format (NTFS here) may be significant - also make sure you have write permission on the files you are updating.	[reply] [d/l] [select]
Re: file timestamp and Windows 7 by Anonymous Monk on Jan 05, 2011 at 07:34 UTC
This works fine on Windows XP but not on Windows 7 (I use Win32::UTCFileTime too). How does it fail, whats the error message? Is something special needed for Windows 7 or is this not supported? perlport says utime Only the modification time is updated. (BeOS, VMS, RISC OS) May not behave as expected. Behavior depends on the C runtime library's implementation of utime(), and the filesystem being used. The FAT filesystem typically does not support an "access time" field, and it may limit timestamps to a granularity of two seconds. (Win32) An examination of the source reveals, just like perlport says, behaviour depends on the c runtimes utime, so I expect it to work much like microsoft says it should :)	[reply]
Re^2: file timestamp and Windows 7 by momo33 (Beadle) on Jan 05, 2011 at 08:03 UTC
Sorry, my mistake: On Windows 7 the file timestamp is not updated as it is updated on Windows XP.	[reply]
Re^3: file timestamp and Windows 7 by Anonymous Monk on Jan 05, 2011 at 08:51 UTC
Sorry, my mistake: On Windows 7 the file timestamp is not updated as it is updated on Windows XP. When it fails to update the timestamp, it should set errno, so what is errno set to? `utime(time, time, $file) or die sprintf "ERRRR(%d)(%s)(%d)(%s)", $!,$!,$^E,$^E;` [download]	[reply] [d/l]
Re^4: file timestamp and Windows 7 by momo33 (Beadle) on Jan 05, 2011 at 10:01 UTC
Re^5: file timestamp and Windows 7 by Anonymous Monk on Jan 05, 2011 at 10:07 UTC
Re: file timestamp and Windows 7 by locked_user sundialsvc4 (Abbot) on Jan 05, 2011 at 13:40 UTC
I know that, say, on Unix/Linux, some filesystems do not routinely support the updating of file timestamps. The calls appear to work but do not actually do anything. The stated reason is efficiency: updating file labels involves a lot of disk I/O and creates “hot spots” in those areas, forcing networked systems to do a lot of cache-invalidation for essentially no good purpose. Usually, this behavior is configurable through some kind of knob. My educated guess is that such a thing might be happening here.
Re^2: file timestamp and Windows 7 by ELISHEVA (Prior) on Jan 05, 2011 at 14:00 UTC
I know that is true for last access time, but last mod time? How would you do backups by date? That's a pretty standard sysadmin activity. Scary if it is true. Do you know of specific examples where last mod time is not tracked by the file system?	[reply]