I can't believe I'd never thought of reordering output columns like this. FWIW, I agree that another option should be used to prevent issues with backward compatibility.
$ echo 1,2,3,4,5,6 | cut -d, -f3,5,2 2,3,5 $ echo 1,2,3,4,5,6 | cut -d, -f3,5,2 -o 3,5,2 Should this be extended to character output as well? echo output | cut -c6,4,2 -o tpu On Wed, Jul 19, 2017 at 8:54 AM, Nellis, Kenneth < kenneth.nel...@conduent.com> wrote: > From: coreutils > Hi, Kaz. > > > > Thanks for the response. I'm happy that you've come to the same > > conclusion > > that I'd reached. I only have a moment for a quick reply now, but my > > inclination was to add a -o / --ordered option to make -f (and other > > options) work the way I'd expected. > > > > I'd be happy to implement the feature myself and contribute it back to > the > > community. I'd just like to know what are the procedures. Should I wait > > for > > the feature request to be approved by someone? I didn't want to spend > > time > > implementing it only to see out rejected soon afterwards. > > > > I've seen the hacking readme and I understand what to do technically. > > However, I couldn't find any documentation about what happens > > procedurally. If you or others can share some insight, I'd appreciate > it. > > > > Thanks in advance. > > > > On Tue, Jul 18, 2017 at 21:06 Kaz Kylheku (Coreutils) < > > 962-396-1...@kylheku.com> wrote: > > > > > 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. > > Indeed, I've wanted this feature for a while. We use QNX4 in our > legacy embedded product, and its cut indeed outputs fields in the > order specified. I was quite surprised when the script I wrote for > QNX4 didn't work with Gnu. > > qnx4> echo 1,2,3,4,5,6 | cut -d, -f3,5,2 > 3,5,2 > qnx4> use cut > cut - cut out selected fields of each line of a file (POSIX) > > cut -c list [file ...] > cut -f list [-d delim] [-s] [file ...] > Options: > -c Cut out the <list> of fields based on character position. > -f Cut out the <list> of fields based on field position. > -d Specify the field delimiter character. > -s Suppress the output of lines which contain no field delimiter. > Where: > list Is a list of character or field positions separated by a <space> > or a <comma>. A range of positions may be specified using the > <hyphen>. > Examples: > cut -c 20-29,40-49 myfile Output character columns 20 to 29 and 40 to > 49 > of the file 'myfile' > cut -f 3,5,7-11 -d| myfile Output fields numbered 3, 5, and 7 to 11 of > the > file 'myfile'. The fields in each input line > are separated by the '|' character. > qnx4> > > I support the change. > > --Ken Nellis > -- :wq
