Uses for access time

[Paul Raveling]

In article <3672 at lynx.UUCP> m5 at lynx.UUCP (Mike McNally (Man from Mars)) writes:
>I am trying to convince some of my ``colleagues'' here that keeping track
>of last-access times of files is a useful pursuit for an operating system.
>...
>Are these reasons enough to justify the overhead (I think so)?  Are there
>other reasons that I am overlooking?


	1.  Automatic file archiving (archive to tape [or whatever]
	    if a file has not been accessed within the last n weeks) --
	    Helps lots, particularly on multi-user systems with
	    marginal amounts of disk space.
	
	2.  Manual identification of files that have been forgotton --
	    On Tenex I frequently got directory listings in reverse
	    chronological order by access time for precisely this purpose.
	
	3.  Checking for surprises -- for example, finding that half
	    of your Lisp modules are being loaded from source and
	    interpreted instead of being loaded from compiled files.

	4.  Security checks.  Something else I used to do occasionally
	    on Tenex was to use directory listings to check for surprises
	    in WHO had last read my files.  (Do any current systems
	    keep track of the identities of the file's creator, last
	    writer, and last reader?)


---------------------
Paul Raveling
Raveling at vaxa.isi.edu