Re: Feature Request / Discussion: `cut` to several files

[Pádraig Brady]

On 25/01/17 01:13, Erik Brinkman wrote:
> It'd be nice if cut allowed writing to several files. I'm not sure what the
> appropriate syntax for something like this would be, but I could see a
> command looking something like:
> 
> cut -f 1,2 filename1 -f 3-5 filename2
> 
> or maybe
> 
> cut -f 1,2:filename1:3-5:filename2
> 
> I don't think the first syntax is posix, and it's definitely not backwards
> compatible. The second might work, but is pretty ugly. I couldn't find
> anything related to this in the archive or in the rejected feature
> requests. Some alternatives with downsides:
> 
>    - Save the buffer and use cut repeatedly on that. The downside is it
>    requires the buffer to be saved.
>    - I managed to throw together an awk script that could be tailored to do
>    similar things. This writes column 1 to file 1, etc for all of the listed
>    files:
> 
>    awk 'BEGIN { NUM = ARGC; if ( ARGC > 2 ) ARGC = 2 } { for ( I = 2; I <
>    NUM; ++I) { print $(I - 1) > ARGV[I] } }' input_file column_1 column_2
> 
>    The nice part is that this works with subprocesses wiithout saving
>    entire intermediate buffers:
>    paste <(seq 1 10) <(seq 11 20) | awk 'BEGIN { NUM = ARGC; if ( ARGC > 2
>    ) ARGC = 2 } { for ( I = 2; I < NUM; ++I) { print $(I - 1) > ARGV[I] } }' -
>    >(paste -sd+ | bc) >(paste -sd+ | bc)
> 
>    However, this is ugly, pretty manual, and doesn't support ranges very
>    easily.
> 
> It seems plausible that cut source could be modified to store a field /
> character list for each file, open up all of them, and write characters /
> fields out on the fly as it normally does with stdout. I'm happy to
> implement this myself and patch, but I'm uncertain if the coreutils team
> views this as an appropriate addition, and if so, what a proper syntax
> would look like. It seems like since this is modifying the field spec of
> cut, it could potentially have ramifications for other field specifications
> in coreutils, although I can't think of any the relate to writing, so it
> may not matter.

Would tee suffice for this use case?

  source_command | tee >(cut -f1,2 >file1) > >(cut -d' ' -f3,5 >file2)

thanks,
Pádraig