RE: [Boost-Users] Re: Why isn't the "last access time" part of the filesystem library?

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2003-05-07 13:27:40

richard_fanta <richard.fanta_at_[hidden]> wrote:
> Beman Dawes <bdawes_at_a...> wrote:
> > At 01:02 AM 5/6/2003, richard_fanta wrote:
> > 
> >  >Looking at the filesystem library and the attributes work in
boost-
> >  >sandbox, I don't immediately see "last access time" being
available
> >  >for a file or directory.
> >  >
> >  >"Last access time" was included in Dietmar Kuehl's original
dir_it.
> >  >
> >  >Can someone kindly tell me why this was removed?  It's highly
useful,
> >  >and part of every filesystem that I've seen.
> > 
> > ISO/IEC 9660:1999 filesystems don't supply a "last access" time
stamp, 
> > perhaps because the original uses were on write-once media.
> 
> Which filesystems adhere to this spec other than CD-ROMs?

Many DVDs use this too, but for most purposes they're basically just
higher-capacity CDs.

> > Perhaps we should do more to support attribute query within the main

> > library, but I don't really think we should include any that aren't 
> > reliably supported by at least POSIX, Windows, and ISO-9660 systems.
> 
> Your point is well made.  However, it does seem odd that a feature 
> that is useful for >95% of all typical usage shouldn't be in the 
> library.

What does that figure refer to, if anything?

> Other options:
>   -For ISO 9660 filesystems, use the time created as the "last 
> access" time stamp.
>   -Throw a "FeatureNotSupportedException" or somesuch.

Then the feature won't be at all portable, and might as well not be
supported at all.  Access times are far from a universal OS feature,
and updates to them may be disabled because the volume is read-only
(whether or not the underlying medium is read-only) or purely to
avoid the cost of updating them.  Note that Windows NT maintains
access times at quite a low resolution, to reduce this cost.