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Subject: |
Sort gives incorrect order when changing delimiters |
Date: |
Mon, 7 Dec 2015 15:36:12 +0000 |
The following problem came to light following a StackOverflow question
[1]. The lexical ordering of sort appears to depend on the delimiter
used, and I believe it shouldn't. As a minimal example:
### Correct ordering ###
$ printf "1,a,1\n2,aa,2" | LC_ALL=C sort -k2 -t,
1,a,1
2,aa,2
### Incorrect ordering by replacing the "," delimiter by "~" ###
$ printf "1~a~1\n2~aa~2" | LC_ALL=C sort -k2 -t~
2~aa~2
1~a~1
I think this is because, in ASCII, "," < "a" < "~".
Many thanks,
Ed
[1]
http://stackoverflow.com/questions/34134677/trying-to-understand-the-sort-utilty-in-linux
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--- Begin Message ---
Subject: |
Re: bug#22109: Sort gives incorrect order when changing delimiters |
Date: |
Mon, 7 Dec 2015 09:49:08 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
tag 22109 notabug
thanks
On 12/07/2015 08:36 AM, Ed Brambley wrote:
> The following problem came to light following a StackOverflow question [1].
> The lexical ordering of sort appears to depend on the delimiter used, and I
> believe it shouldn't. As a minimal example:
Thanks for the report. However, you have not found a bug in sort, only
in your misuse of the command line and in your incorrect assumptions.
Let's investigate further with the --debug option:
>
> ### Correct ordering ###
> $ printf "1,a,1\n2,aa,2" | LC_ALL=C sort -k2 -t,
> 1,a,1
> 2,aa,2
$ printf '1,a,1\n2,aa,2' | LC_ALL=C sort -k2 -t, --debug
sort: using simple byte comparison
1,a,1
___
_____
2,aa,2
____
______
You are comparing the string "a,1" with "aa,2"; so the relative relation
between ',' and 'a' matters.
>
> ### Incorrect ordering by replacing the "," delimiter by "~" ###
> $ printf "1~a~1\n2~aa~2" | LC_ALL=C sort -k2 -t~
> 2~aa~2
> 1~a~1
Same goes for here.
$ printf '1~a~1\n2~aa~2' | LC_ALL=C sort -k2 -t~ --debug
sort: using simple byte comparison
2~aa~2
____
______
1~a~1
___
_____
You compared the string "aa~2" with "a~1".
>
> I think this is because, in ASCII, "," < "a" < "~".
Yes, so you saw exactly what you asked for. But what you asked for
("sort starting from the second delimiter through to the end of the
line") is probably not what you wanted. It sounds like you wanted "sort
on ONLY the second delimiter", which is spelled differently:
$ printf '1~a~1\n2~aa~2' | LC_ALL=C sort -k2,2 -t~ --debug
sort: using simple byte comparison
1~a~1
_
_____
2~aa~2
__
______
Note that there is a very distinct difference between '-k2' and '-k2,2';
only the latter one limits the sort to JUST the second key ("a" vs.
"aa", regardless of delimiter), while the former slurps in the rest of
the line such that the spelling of the delimiter affects the result.
I'm marking this as not a bug in the database, but feel free to add
further comments.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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