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RE: IFS file Created, Accessed and Changed info



fixed

You are spot on John, I did misread; thanks you!

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of John Yeung
Sent: Thursday, May 29, 2014 12:26 PM
To: Midrange Systems Technical Discussion
Subject: Re: IFS file Created, Accessed and Changed info

On Thu, May 29, 2014 at 1:53 PM, Gary Thompson <gthompson@xxxxxxxxxxx> wrote:
All of this by my assumption, from reading, that other systems may
update Changed date on access alone.

If you got that from me, then you probably misread the following:

From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
John Yeung
There's a system call named "stat" on both Unix and Windows, that
retrieves three times. "Access" time and "content modification"
time have the same meaning on both systems,

The above is saying that
(1) The meaning of "access" time on Unix is the same as the meaning of "access" time on Windows.
(2) The meaning of "content modification" time on Unix is the same as the meaning of "content modification" time on Windows.

That was to contrast with the third time, which has a different meaning on Unix than it does on Windows.

I keep saying "the third time". What I really mean is the "ctime".
The access time and modification time are named "atime" and "mtime", respectively. I really wanted to avoid bringing up actual names used in implementation, just as I try to avoid using actual DDS field names when talking to users about what's in the database. But in this case, maybe knowing the raw names sheds some light on things. For the morbidly curious (or bored), here is a nice article on the "stat"
system call (focusing on Unix, which is where it originated):

http://en.wikipedia.org/wiki/Stat_%28system_call%29

There is even a section in there specifically about ctime.

But the main takeaway that I was going for was that timestamps are fundamentally unreliable, on any computer system whatsoever. Your best bet is, if possible, to use techniques which don't depend on timestamps at all. Some ideas for doing that were mentioned by others in this thread.

John Y.
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