uniq with sort-like "--key" support

[Assaf Gordon]

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

0001-uniq-support-sort-like-key-specification.patch.xz
Description: application/xz