Re: coreutils feature requests?

[Kaz Kylheku (Coreutils)]

On 18.07.2017 15:44, Lance E Sloan wrote:
> Hi, all.
>
> Aside from a bug report, is there a way to submit a feature request for
> coreutils?  I have a couple of requests in mind, which I don't think
> qualify as bugs:
>
> 1. Add a feature to "cut" that allows selected fields to be output in a
> different order.  That is "cut -f4,1,8-6" would cause it to output 
> fields
> in the order of 4, 1, 8, 7, and 6.

I'm amazed that it doesn't work this way; the utility of implicitly
sorting the fields appears low compared to the damage that it does
to the flexibility of cut. (What little it has!)

If POSIX specifies it, I have to say that its requirements are
suboptimal (as is often the case in diverse areas).

Indeed, the requirement is sadly given as:

   The elements in list can be repeated, can overlap, and can be 
specified
   in any order, but the bytes, characters, or fields selected shall be
   written in the order of the input data. If an element appears in the
   selection list more than once, it shall be written exactly once.

Do people often write cut specifications in ad hoc orders, with
repetitions and then rely on the sorting behavior?

The GNU implementation of cut could lead standardization in this
area to improve things.

All the possible solutions to make cut not sort the fields or
de-duplicate them are ugly. Either you  need a global option to
opt out of that behavior, like "-o" (preserve (o)rder) and
keep remembering to use it, or else provide order-preserving
versions of the various options, like perhaps through capitalization:
-F, -C, -B.

An attractive alternative is to have a whole new command which
mirrors cut, like say "clip", which is exactly like cut, but
order and repetition preserving.

Note that the --complement option is semantically incompatible with
order-preserving mode; the complement concept follows from the
selected elements being regarded as a set rather than ordered
sequence. If -F, -C or -B is used with --complement, it has to be
diagnosed.  Or if there is a "clip" command, then that simply
doesn't support --complement.