GNU bug report logs - #32250
doc: ls: explain atime/mtime/ctime better

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: kalle <kalle <at> projektwerkstatt.de>
To: bug-coreutils <at> gnu.org
Subject: ls -explain better the different times
Date: Mon, 23 Jul 2018 17:54:42 +0200

hello,
in the documentation of ls the concept of the different times is not
explained sufficiently well (mtime, atime, ctime).
greetings,
kalle

Message #12 received at 32250 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: kalle <kalle <at> projektwerkstatt.de>, 32250 <at> debbugs.gnu.org
Subject: Re: bug#32250: ls -explain better the different times
Date: Sun, 30 Dec 2018 21:13:30 -0700

[Message part 1 (text/plain, inline)]

Hello,

On 2018-07-23 9:54 a.m., kalle wrote:
> in the documentation of ls the concept of the different times is not
> explained sufficiently well (mtime, atime, ctime).

The dedicated file-timestamp section (
https://www.gnu.org/software/coreutils/manual/html_node/File-timestamps.html 
) is indeed perhaps a bit too dense (lots of text
with no quick examples).

Attached is an improvement suggestion, adding a summary table,
and details examples.

Comments and feedback welcomed,
 - assaf

[0001-doc-expand-file-timestamp-section-atime-ctime-mtime.patch (text/x-patch, attachment)]

Message #15 received at 32250 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Assaf Gordon <assafgordon <at> gmail.com>, kalle <kalle <at> projektwerkstatt.de>,
 32250 <at> debbugs.gnu.org
Subject: Re: bug#32250: ls -explain better the different times
Date: Mon, 31 Dec 2018 00:05:02 -0800

Assaf Gordon wrote:
> Attached is an improvement suggestion, adding a summary table,
> and details examples.
> 
> Comments and feedback welcomed,

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?

Also, some of the entries look too system-specific.  For example, POSIX doesn't 
require that 'ls DIR' must update the access time of DIR, many systems don't 
update access times even when POSIX says they should, and on some systems 
symbolic links' timestamps are irrelevant and/or unchangeable.

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.

Message #18 received at 32250 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>, kalle <kalle <at> projektwerkstatt.de>,
 32250 <at> debbugs.gnu.org
Subject: Re: bug#32250: ls -explain better the different times
Date: Mon, 31 Dec 2018 01:47:10 -0700

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

Message #21 received at 32250 <at> debbugs.gnu.org (full text, mbox):

From: kalle <kalle <at> projektwerkstatt.de>
To: Assaf Gordon <assafgordon <at> gmail.com>, 32250 <at> debbugs.gnu.org
Subject: Re: bug#32250: ls -explain better the different times
Date: Mon, 31 Dec 2018 22:10:19 +0100

hello,
i'm happy that so much later someone cares about my bug-report.

Am 31.12.2018 um 05:13 schrieb Assaf Gordon:
> Hello,
> 
> On 2018-07-23 9:54 a.m., kalle wrote:
>> in the documentation of ls the concept of the different times is not
>> explained sufficiently well (mtime, atime, ctime).

I'm sorry to discover that when I wrote these lines, I referred to
version 8.26-3, while it was not the most actual. The section "File
timestamps" didn't exist then.

However, I still believe that the times are not described precisely
enough by the terms "write","read","change" until it is totally clear,
what is meant by these (it is not totally clear to me).

Therefore I welcome your summary table, although not being able to read
it, since it's only a patch.

> 
> The dedicated file-timestamp section (
> https://www.gnu.org/software/coreutils/manual/html_node/File-timestamps.html
> ) is indeed perhaps a bit too dense (lots of text
> with no quick examples).
> 
> Attached is an improvement suggestion, adding a summary table,
> and details examples.
> 
> Comments and feedback welcomed,
>  - assaf
> 
> 

greetings,
kalle

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