Re: SV: Wish: checksumming *sum filter

[Pádraig Brady]

On 10/05/19 06:13, Ole Tange wrote:
> Pádraig wrote:
> 
> :
> 
>> The fact that *sum would need to consume/buffer all the input would mean 
>> that the parallelism
>> from the rest of the pipe is lost (well I suppose the process startup 
>> overhead is parallelized).
> 
> Just like sort/wc and *sum if used in a pipe today:
> 
>     cat file | sha256sum | ...

Right.

*sum, and wc are simple as they reduce the input to a bounded size.

sort is not simple internally and must deal with
writing out temp files.

>> I.E. it's functionally equivalent to:
>>
>>  Get_untrused_input > /tmp/blah
>>  sha256sum -c <(echo "$chksum  /tmp/blah") &&
>>  ...
>>  rm /tmp/blah
> 
> Yes, except you can do it on a read-only file system and in a shell that does 
> not support <().

In the general case write access would probably be required, like with sort 
above.
Note sort uses $TMPDIR if set to identify a writable file system.
Re support for <(), one could use another temp file for that.

cheers,
Pádraig