Re: who: sorted output + minor usage change

[Pádraig Brady]

On 09/02/15 19:52, Assaf Gordon wrote:
> Hello Pádraig,
> 
> On 02/09/2015 05:49 AM, Pádraig Brady wrote:
>> On third thought, perhaps we should tweak the output from who to be more 
>> easily processed?
>> It seems like small tweaks could improve things a lot, and would be a more 
>> general solution.
> 
> Agreed.
> though I don't know if the output of 'who' is commonly used with automated 
> parsing, and thus expected not to change?

Given the awkwardness of parsing,
I doubt changes to add placeholders would impact anything significant.

>> The time field can already be sorted with `sort -b -k3,4` (we should remove 
>> the locale variant)
> 
> This could be a bit problematic depending on the options used.
> For example, with "-a", I get the following on my system:
> ====
> $ ./src/who -a
>            system boot  2015-02-02 17:24
>             run-level 2  2015-02-02 17:24
> LOGIN      tty4         2015-02-02 17:24              1901 id=4
> LOGIN      tty5         2015-02-02 17:24              1905 id=5
> LOGIN      tty2         2015-02-02 17:24              1914 id=2
> gordon   - tty3         2015-02-06 16:46  old        12643
> LOGIN      tty6         2015-02-02 17:24              1919 id=6
> gordon   - tty1         2015-02-04 19:53  old         6103
> gordon   ? :0           2015-02-02 17:24   ?          4694 (:0)
> gordon   + pts/0        2015-02-02 17:28   .          5894 (:0)
> gordon   + pts/12       2015-02-02 17:28  old         5894 (:0)
> gordon   + pts/16       2015-02-05 10:49 00:04        5894 (:0)
>             pts/17       2015-02-04 20:53             24776 id=s/17  term=0 
> exit=0
>             pts/26       2015-02-06 22:08                 0 id=/26   term=0 
> exit=0
>             pts/27       2015-02-04 17:03                 0 id=/27   term=0 
> exit=0
> ====
> So the third and fourth fields (determined by whitespace) are not always the 
> login time.

Right. So we'd have placeholders for empty fields.
 '.' for NAME (to match solaris)
 '.' for the -T column as previously discussed
 '-' for the IDLE column (so not clashing with "." there

> Also noticed that in POSIX locale, the time string must be "%b %e %H:%M" (in 
> the example above, the locale was en_US.UTF-8, and the time string was 
> "%Y-%m-%d %H:%M") - so there's another white space in POSIX locale.

Oh right, POSIX states to use "%b %e ...".
That's still quite processable, though a little more awkward to sort on that 
field.

> But since my original intention was to simply find "logged in users sorted by 
> idleness",
> I guess using this can be assumed to always work:
>     $ LC_ALL=C who -u | sort -b -k6,6

Yes that should work reliably.

I'll look about adding placeholders so that who -a is processable.

thanks!
Pádraig.