Re: bin/51726: sort -n ignored if given after -k

[Abhinav Upadhyay <er.abhinav.upadhyay%gmail.com@localhost>]

On Sun, Dec 18, 2016 at 9:54 PM, Abhinav Upadhyay
<er.abhinav.upadhyay%gmail.com@localhost> wrote:
> On Sun, Dec 18, 2016 at 1:55 PM, Robert Elz <kre%munnari.oz.au@localhost> wrote:
>> The following reply was made to PR bin/51726; it has been noted by GNATS.
>>
>> From: Robert Elz <kre%munnari.OZ.AU@localhost>
>> To: gnats-bugs%NetBSD.org@localhost
>> Cc:
>> Subject: Re: bin/51726: sort -n ignored if given after -k
>> Date: Sun, 18 Dec 2016 15:23:38 +0700
>>
>>      Date:        Sun, 18 Dec 2016 02:05:01 +0000 (UTC)
>>      From:        David Holland <dholland-bugs%netbsd.org@localhost>
>>      Message-ID:  <20161218020501.468347A302%mollari.NetBSD.org@localhost>
>>
>>    |  If you're using -k you're supposed to put the key flags in the -k
>>    |  argument, that is, sort -k 3nr.
>>
>>  Not quite, using global options is still fine, they're just not
>>  supposed to apply to a key specified if that key has any sort selections
>>  of its own.
>>
>>  Our sort doesn't do that, it merges global options and key specific
>>  options, in a kind of weird way --- but the behaviour described (while
>>  perhaps not strictly correct) is I think what is intended.
>>
>>  That is, when sorting a key field, you get whatever sort options are
>>  specified for that key, merged with whatever global options had already
>>  been given - later global options are supposed to affect the next key
>>  (or the backup default sort if the keys are equal).   That is, that's how
>>  the NetBSD sort is written.
>>
>>    |  Technically I think if you write -k 3 -n -r and it doesn't honor the
>>    |  -n it's doing what you asked.
>>
>>  According to our sort's design, yes, though I don't think that is posix.
>>
>>    | And I think if you write -k 3 -n -r and
>>    | it *does* sort in reverse order, then *that*'s a bug. sigh.
>>
>>  Yes, probably.
>>
>>    |  sort's argument handling is a trainwreck.
>>
>>  That mild?
>>
>>    |  And thus the code in sort that deals with it is horrifying.
>>
>>  Yes.   We could probably simplify it a lot if we made it posix
>>  conformat (where any key specific ordering options disable all
>>  the globals for that key) but it has been as it is for a long time
>>  now (mayve even, modulo the k stuff) has been like it since 6th or
>>  7th edition unix.   So changing it might break a lot - who knows?
>
> I have been going over the sort(1) man page from posix, and at one
> place (in the APPLICATION USAGE section) it says the following about
> the use of ordering options after -k:
>
> "The wording in the OPTIONS section clarifies that the -b, -d, -f, -i,
> -n, and -r options have to come before the first sort key specified if
> they are intended to apply to all specified keys. The way it is
> described in this volume of POSIX.1-2008 matches historical practice,
> not historical documentation. The results are unspecified if these
> options are specified after a -k option."
>
> So, I guess using `sort -k3 -n -r` is undefined behavior?. That said,
> the example mentioned in the PR (sort -k 2 -n -r) does work with GNU
> sort(1). I had a patch ready yesterday, so just posting it here :)
>
> This patch lets sort(1) associate -b, -d, -f, -i, -n, -r options to
> specific fields if specified after -k.  All ATF tests for sort(1) are
> passing except for a couple of cases in kflag_alpha, but they look
> ambiguous to me and one of the similar tests is commented out as
> broken. If we want to accept this behavior in our sort(1) and the
> patch looks in the right direction, I will try to dig in and get those
> test cases passing  :)
>
> http://www.netbsd.org/~abhinav/sort.c.diff

Just tested on OpenBSD and FreeBSD, their sort(1) also supports -n after -k.

-
Abhinav