Re: [PATCH] strverscmp.3: this is NOT the ordering used by ls -v

[Alejandro Colomar <alx@kernel.org>]

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Hi nab,

On Sun, Dec 15, 2024 at 09:17:59PM +0100, Ahelenia Ziemiańska wrote:
> Compare, given:
> 	#include <stdlib.h>
> 	#include <stdio.h>
> 	#include <string.h>
> 	int compar(const char **l, const char **r) {
> 		return strverscmp(*l, *r);
> 	}
> 	int main(int argc, char ** argv) {
> 		qsort(argv + 1, argc - 1, sizeof(*argv), compar);
> 		for(int i = 1; i <  argc; ++i)
> 			puts(argv[i]);
> 	}
> yields:
> 	$ /bin/ls -v1 a*  # coreutils ls
> 	a-1.0a
> 	a-1.0.1a
> 	$ ../vers a*      # as above
> 	a-1.0.1a
> 	a-1.0a
> 	$ ls -v1 a*       # voreutils ls @ 5781698 with strverscmp()-equivalent sorting
> 	a-1.0.1a
> 	a-1.0a

Should we file a bug against glibc strverscmp(3)?  We probably should.

> compare also the results for real data like
> 	netstat-nat-1.{0,1{,.1},2,3.1,4{,.{1,2,3,4,5,6,7,8,9,10}}}.tar.gz

> 
> Thus, coreutils ls -v does NOT use strverscmp(3),
> it uses a similar algorithm that actually properly sorts versions,
> not just single numbers.

First time I learn about ls(1) having a -v option.  :|
Was people too lazy to type `ls | sort -V`?

> 
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
> ---
>  man/man3/strverscmp.3 | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/man/man3/strverscmp.3 b/man/man3/strverscmp.3
> index 41bc1ddbd..7c3643860 100644
> --- a/man/man3/strverscmp.3
> +++ b/man/man3/strverscmp.3
> @@ -25,16 +25,7 @@ .SH DESCRIPTION
>  orders them
>  .IR jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 .
>  .\" classical solution: "rename jan jan0 jan?"
> -In order to rectify this, GNU introduced the
> -.I \-v
> -option to
> -.BR ls (1),
> -which is implemented using
> -.BR versionsort (3),
> -which again uses
> -.BR strverscmp ().
> -.P
> -Thus, the task of
> +The task of
>  .BR strverscmp ()
>  is to compare two strings and find the "right" order, while
>  .BR strcmp (3)
> @@ -44,6 +35,10 @@ .SH DESCRIPTION
>  .BR LC_COLLATE ,
>  so is meant mostly for situations
>  where the strings are expected to be in ASCII.
> +This is not actually the ordering produced by
> +.BR ls (1)
> +.BR -v .
> +.\" because it considers a-1.0.1a < a-1.0a; this is not what you want

I hate this reference to ls(1).  ls(1) should not even have a -v option.
Please refer to sort(1) instead.  I would wipe any references to file
names in this page, as I don't think they are relevant at all.

And the reference to sort(1), I'd put it in BUGS, saying that this API
is broken, and does not sort properly.  Sounds good?

Have a lovely night!
Alex

>  .P
>  What this function does is the following.
>  If both strings are equal, return 0.
> -- 
> 2.39.5



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