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Re: SV: Wish: checksumming *sum filter

From: Pádraig Brady
Subject: Re: SV: Wish: checksumming *sum filter
Date: Fri, 10 May 2019 07:44:21 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0

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 | ...


*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 
Note sort uses $TMPDIR if set to identify a writable file system.
Re support for <(), one could use another temp file for that.


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