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bug#23556: sort(1): misleading description of option -n
From: |
Eric Blake |
Subject: |
bug#23556: sort(1): misleading description of option -n |
Date: |
Mon, 16 May 2016 13:35:48 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 05/14/2016 08:17 AM, Carsten Hey wrote:
> Hi,
>
> the man page sort(1) contains a misleading description of the option -n:
> compare according to string numerical value
That sounds accurate to me, although as Assaf pointed out, suggested
wording improvements are welcome.
> $ printf '%s\n' 'x 9' 'x 10' | sort -n
> x 10
> x 9
The numerical value of "x 10" (that is, the equivalent to the value of
atoi("x 10")), is "0". To check:
$ printf '%s\n' 'x 9' 'x 10' '1' '-1' | sort -n
-1
x 10
x 9
1
If you want to sort by the second column only, then use:
$ printf '%s\n' 'x 9' 'x 10' | sort -n -k 2,2
x 9
x 10
That is, by adding the -k option, you can limit the text being sorted to
the portion of the line containing the numerical value, rather than the
entire line, so as to avoid a numerical value of 0 when hitting a
non-numeric portion of the line.
> …, but instead, -n stops doing its magic after finding the first
> non-numeric, non-whitespace character.
Because that is how it has always behaved, and how POSIX requires it to
behave.
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sort.html
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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