On Sun, Dec 15, 2024 at 10:44:26PM +0100, Alejandro Colomar wrote:
> On Sun, Dec 15, 2024 at 10:02:42PM +0100, наб wrote:
> > > Should we file a bug against glibc strverscmp(3)? We probably should.
> > >
> > > 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?
> > No, this API works as-documented, and the implementation is useful.
> What does useful mean?
There are applications where a lexicographical-except-numeric comparison
like this is what you want (it's most of them). Calling it a "version
sort is silly + goofy but, whatever.
> > It's just not what ls -v does.
> While version sort isn't something standard, I think GNU should be
> self-consistent.
It is, ls -v and sort -V are consistent.
Having just implemented the /actual/ algorithm they use for voreutils,
that is by far /not/ universally applicable, much hairier, and hard-tuned for
"versions that are kinda like debian describes and sorts them (but not actually)
AND ALSO we put them in filenames where we can assume the format a little bit
AND ALSO {4 special cases to make ls -v work}".
Replacing this well-defined lexicographical-except-numeric sorter with... that,
isn't really applicable.
Best,
-- >8 --
From: =?UTF-8?q?Ahelenia=20Ziemia=C5=84ska?=
<nabijaczleweli@xxxxxxxxxxxxxxxxxx>
Subject: [PATCH v3] strverscmp.3: this is NOT the ordering used by ls -v
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
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 modified Debian version comparison algorithm with additional
suffix processing and ls -v-specific exceptions.
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
man/man3/strverscmp.3 | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/man/man3/strverscmp.3 b/man/man3/strverscmp.3
index 41bc1ddbd..e028d6788 100644
--- a/man/man3/strverscmp.3
+++ b/man/man3/strverscmp.3
@@ -18,25 +18,14 @@ .SH SYNOPSIS
.BI "int strverscmp(const char *" s1 ", const char *" s2 );
.fi
.SH DESCRIPTION
-Often one has files
+For a dataset like
.IR jan1 ", " jan2 ", ..., " jan9 ", " jan10 ", ..."
-and it feels wrong when
-.BR ls (1)
-orders them
+sorting it lexicographically yields
.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
+is to compare two strings yielding the former order, while
.BR strcmp (3)
finds only the lexicographic order.
This function does not use
@@ -44,6 +33,10 @@ .SH DESCRIPTION
.BR LC_COLLATE ,
so is meant mostly for situations
where the strings are expected to be in ASCII.
+This is different from the ordering produced by
+.BR sort (1)
+.BR -V .
+.\" sort -V sorts a-1.0a < a-1.0.1a; strverscmp() does not
.P
What this function does is the following.
If both strings are equal, return 0.
--
2.39.5
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