Re: RFC: improved support for grouping in uniq (original) (raw)

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From: Eric Blake
Subject: Re: RFC: improved support for grouping in uniq
Date: Wed, 02 Mar 2011 09:57:13 -0700
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Lightning/1.0b3pre Mnenhy/0.8.3 Thunderbird/3.1.7

On 03/02/2011 09:44 AM, Pádraig Brady wrote:

-d, -D and -u make sense when used in isolation:

$ printf "1 a\n2 a\n2 b\n2 c\n3 a\n" | uniq -w1 -D 2 a 2 b 2 c $ printf "1 a\n2 a\n2 b\n2 c\n3 a\n" | uniq -w1 -u 1 a 3 a pb-laptop:~$ printf "1 a\n2 a\n2 b\n2 c\n3 a\n" | uniq -w1 -d 2 a

However when you combine -u (suppress last output entry in a repeated group) with -d or -D it doesn't seem useful:

$ printf "1 a\n2 a\n2 b\n2 c\n3 a\n" | uniq -w1 -d -u

This behavior is required by POSIX (-d suppresses unique lines, -u suppresses duplicate lines, so all lines are suppressed).

$ printf "1 a\n2 a\n2 b\n2 c\n3 a\n" | uniq -w1 -D -u 2 a 2 b

-D is a GNU invention, so we are free to make it more useful.

Why I'm asking is to perhaps overload -u -D to support grouping like:

$ printf "1 a\n2 a\n2 b\n2 c\n3 a\n" | uniq -w1 --unique=separated --all-repeated=separated 1 a

2 a 2 b 2 c

3 a

Or maybe we should just add a new --group option to do the above?

A --group option sounds interesting, even in combination with the others:

$ printf "1 a\n2 a\n2 b\n3 a\n3 b\n4 a\n" | uniq -w1 -u --group 1 a

4 a $ printf "1 a\n2 a\n2 b\n3 a\n3 b\n4 a\n" | uniq -w1 -D --group 2 a 2 b

3 a 3 b $ printf "1 a\n2 a\n2 b\n3 a\n3 b\n4 a\n" | uniq -w1 --group 1 a

2 a 2 b

3 a 3 b

4 a

-- Eric Blake address@hidden +1-801-349-2682 Libvirt virtualization library http://libvirt.org

Attachment: signature.asc
Description: OpenPGP digital signature