[R] Does file.info man page describe ctime corrrectly?
Prof Brian Ripley
ripley at stats.ox.ac.uk
Fri Dec 19 10:47:30 CET 2008
This really is a topic for R-devel ... see the posting guide.
On Fri, 19 Dec 2008, Graham Williams wrote:
> (R 2.8.0 on Debian GNU/Linux sid)
> ?file.info contains:
> mtime, ctime, atime: integer of class '"POSIXct"': file modification,
> creation and last access times.
> This implies that ctime is "file [...] creation [...] time"
> Has R implemented ctime differently to Unix?
> I understand, on Linux at least, that ctime is the last change time
> (not the creation time). See "man ls" which says:
> -c [...] ctime (time of last modification of file status
> information) [...]
'man stat' would be more definitive, and
even more so (but only for POSIX-compliant OSes). As you will see, there
is considerable room for interpretation even under POSIX.
> However, testing seems to indicate file.info is returning the change
> time, not creation time (I'm not sure we can actually determine
> creation time of a file on Linux).
> Perhaps just a file.info documentation slip?
Well, to call it 'last change' would indeed be a documentation slip.
What it does depends on the OS and file system, but on Linux it is the
last *status* change, which is often the creation time (modifying the file
does not necessarily change the status). On Windows it *is* the creation
time, and that means it is too on a SMB-mounted Windows file system on
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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