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bug#9334: sort bug

From: Aaron Davies
Subject: bug#9334: sort bug
Date: Mon, 22 Aug 2011 00:11:12 -0400

On Sunday, August 21, 2011, Bob Proulx <address@hidden> wrote:
> tags 9334 + notabug
> thanks
>> First: some version information:
>> sort (GNU coreutils) 8.4
> Thanks!
>> I run a series of pipes, and after piping into 'sort -n', I see this:
>>     1   12
>>     1    4
>>     5   16
>>     9   20
>> The first column sorted correctly, numerically, but the second did not.
>> I do not have sufficient data to determine whether the second column
>> is sorted lexicographically, or simply ignored.
> Thanks for the report but you are not seeing a bug in sort but in the
> use of it.  You have insufficiently qualified the sort criteria.  Try
> this:
>  sort -n -k1,1 -k2,2
> Or my preference:
>  sort -k1,1n -k2,2n
> The reasoning is as found in the sort documentation:
>     A pair of lines is compared as follows: `sort' compares each pair of
>  fields, in the order specified on the command line, according to the
>  associated ordering options, until a difference is found or no fields
>  are left.  If no key fields are specified, `sort' uses a default key of
>  the entire line.  Finally, as a last resort when all keys compare
>  equal, `sort' compares entire lines as if no ordering options other
>  than `--reverse' (`-r') were specified.  The `--stable' (`-s') option
>  disables this "last-resort comparison" so that lines in which all
>  fields compare equal are left in their original relative order.  The
>  `--unique' (`-u') option also disables the last-resort comparison.
>  ...
>  `-n'
>  `--numeric-sort'
>  `--sort=numeric'
>       Sort numerically.  The number begins each line and consists of
>       optional blanks, an optional `-' sign, and zero or more digits
>       possibly separated by thousands separators, optionally followed by
>       a decimal-point character and zero or more digits.  An empty
>       number is treated as `0'.  ...
> Since no fields are specified sort is using a default key of the
> entire line.  Since you care about sorting on fields you should
> include sort field options.

Out of curiosity, what's the output mean in this case? "two lines, starting
with the number one, in their original order", "two lines, starting with the
number one, also containing the strings '12' and '4' and sorted
lexicographically thereby", or something else entirely?

Aaron Davies

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