Re: uniq with sort-like "--key" support

[Pádraig Brady]

On 02/12/2013 01:31 AM, Assaf Gordon wrote:
> Hello,
>
> I'd like to offer a proof-of-concept patch for adding sort-like "--key" support 
> for the 'uniq' program, as discussed here:
>    http://lists.gnu.org/archive/html/bug-coreutils/2006-06/msg00211.html
> and in several other threads.
>
> The patch involves few core changes:
> 1. All key-related functions were copied as-is from "sort.c", and put in a separate file 
> (uniq_sort_common.h). In theory, those could extracted later on to file that will be used by both sort 
> and uniq. At the moment, it's a hodge-podge of copy&paste, including code that's not relevant to 
> uniq (like "reverse").
>
> 2. The function "check_files" was modified to convert "struct linebuffer" (used by uniq) 
> to "struct line" (used by sort's functions)
>
> and then
>
> 3. The "different" function was modified to call sort's "keycompare" function.
>
> 4. In main(), the key argument passing was copied from 'sort', and some code was added to 
> adapt previous options (e.g. skip-fields/skip-chars/check-chars) to internal "struct 
> keyfield" .
>
> The result is that uniq can now do:
> ===
> $ printf "A 1\nA 2\nB 2\n" | ./src/uniq -k1,1
> A 1
> B 2
> $ printf "A 1\nA 2\nB 2\n" | ./src/uniq -k2,2
> A 1
> A 2
> ===
>
> Most (but not all) of the existing tests pass.
> New tests to demonstrate the new possibilities have been added to 
> 'tests/misc/uniq-key.pl', try with:
>   make check TESTS=tests/misc/uniq-key SUBDIRS=.
>
> I think that most of the keycomparison functions (like 
> numeric/general-numeric/month/version/skip-blanks) would "just work", though I 
> haven't tested it thoroughly yet.
>
>
> Comments are welcomed,
> -gordon

I'm not going to look at it this week, but thank you!
Consolidating the field processing in a central place
is really good, and it can then be enhanced in future
to support multibyte chars etc.

cheers,
Pádraig.