Re: Feature Request shaXXXsum pipeout

[Pádraig Brady]

On 16/12/2020 16:06, Stefan Althöfer wrote:
> Hi all,
>
> I'd like to request a new --pipeout feature for shaXXXsum to allow on-the-fly 
> checking of files. It should be possible to request shaXXXsum to pass stdin 
> data to stdout.
>
> I'd like to do s.th. like this to avoid reading files twice from network or 
> storing them locally:
>       $ set -o pipefail
>       $ cat network_path/big.img.gz | sha256sum --pipeout -c cs.sha256 | gzip 
> -d | dd of=/dev/sdx
>
> --pipeout should imply --quiet of course and just return nonzero on fails.
>
> It did a test implmentation for sha256 case. Seems this can be implemented 
> easily. Maybe my implementation is not bullet proof however.
>
> Questions to the maintainers:
> . Is such a feature desirable/acceptable?
> . If so, can --pipeout be used or should there be a better option name?
> . Should there be a single letter option?

A similar suggestion was discussed 
at:https://lists.gnu.org/archive/html/coreutils/2019-05/msg00025.html
That was slightly different as it proposed consuming
all the data before outputting anything.

If one was OK in consuming the data in parallel
you might use tee to do the check? Something like:

  ... | tee >(sha256sum -c cs.sha256 || touch cs.fail) | ...
  test -f cs.fail && { rm cs.fail; exit 1; }

cheers,
Pádraig