Re: uniq: missing option -W / --check-fields=N

[Jim Meyering]

Matt Keenan <address@hidden> wrote:
> Jim Meyering wrote:
>> [snip snip]
>>   I agree, and think I wrote exactly the same thing: uniq needs the
>> same
>> -k key-selection options as sort -- probably in response to a request
>> to integrate the Debian patch.  I went to look for it a couple days ago,
>> but got side-tracked.
>
> I am happy to write a patch. Just a quick note, I would have thought
> that the Debian patch was released under a GPL license, and hence I
> wouldn't need to request permission (as the permission was already
> granted by the license). I will check the license anyway before I check
> the code and do a clean room implementation from scratch if necessary..

Hi Matt,

I'm glad you're willing to work on this.
It's an often-requested feature.
Unfortunately, the Debian -W patch was not acceptable.
It did not allow the same flexibility that sort does in
selecting keys.  To provide that, GNU uniq will eventually
accept at least the following options, just as sort does:

  -k, --key=POS1[,POS2]     start a key at POS1, end it at POS2 (origin 1)
  -t, --field-separator=SEP  use SEP instead of non-blank to blank transition
  -z, --zero-terminated     end lines with 0 byte, not newline

and even most, if not all, of these (for flexibility/interoperability
with sort, as well as to ease code sharing between uniq and sort):

  -b, --ignore-leading-blanks  ignore leading blanks
  -d, --dictionary-order      consider only blanks and alphanumeric characters
  -f, --ignore-case           fold lower case to upper case characters
  -g, --general-numeric-sort  compare according to general numerical value
  -i, --ignore-nonprinting    consider only printable characters
  -M, --month-sort            compare (unknown) < `JAN' < ... < `DEC'
  -n, --numeric-sort          compare according to string numerical value
  -r, --reverse               reverse the result of comparisons

This means that there will be an additional challenge: find a clean
way to share the code in sort.c that implements the above options.

As for paperwork, the GNU project requires a copyright assignment and/or
disclaimer of anyone who ends up contributing more than about 10 lines
of code.  If you're still interested, let me know and we can get the
paperwork started -- that process can easily take longer than writing
the code, so it's best to start asap.

Jim