bug#32250: ls -explain better the different times

[Assaf Gordon]

Hello Paul,

On 2018-12-31 1:05 a.m., Paul Eggert wrote:
> Assaf Gordon wrote:
> > Attached is an improvement suggestion, adding a summary table,
> > and details examples.
> >
> > Comments and feedback welcomed,

Thank you for reviewing and providing feedback - goes to show
that things aren't that easily clear (no from anecdotal testing
and not from reading my text).

Before I go on - do you (and others) think it's worthwhile expanding
the timestamp section? if not, I won't spend more time on it.

If yes, then:

> I'm afraid that table goes into so much detail that it will overwhelm 
> the user. Why, for example, have separate lines for chmod and chown?

chown/chmod can indeed by merged, or one of them omitted.

there's a tradeoff between being detailed (helping new users to easily 
find information without too much reading) and being too verbose. I'm
sure couple of further iterations will improve the text.

> Also, some of the entries look too system-specific. [...]

Very good point - that will likely stumble users as well.

We can perhaps explicitly say that some of these are system specific,
or remove the system-specific ones?

> Also, since when does "cp -p a b" not update a's access time? 
> Traditional 'cp' does update the source's access time, and POSIX seems 
> to require that.

Thanks for pointing this out.

I went back and double-checked: on my system (linux 4.9.65-3+deb9u1,
ext4 filesystem mounted  with relatime),
the first time a file is copied  with "cp -p a b", a's access time is
updated. if "a" is then copied few more times, its atime remains the
same, and the new files get its same atime (i.e., not the current time).

IIUC, this is the effect of "relatime" and the fact the "a" was not
modified between coping (However I could be wrong).

In any case, the table should be corrected, and perhaps this issue
should be clarified.


thanks again,
 - assaf