[ale] Fun bash thing

[Pete Hardie]

Does diff not have enough options to get you the "in A but not in B" info?

On Sat, Nov 9, 2024 at 10:35 AM Jim Kinney via Ale <ale at ale.org> wrote:

> I've done similar but usually output to a different file using the
> some-command as an extractor/processor often for line-by-line mangling. Did
> not know it dumps the entire input file into memory first. Hmm. That has
> possibilities as well as potential gotchas related to size. Usually the
> memory is not a problem but if the system is already in heavy use it could
> be impactful.
>
> Nice. Very nice.
>
> My latest fun toy is a grep to find what is in fileA that's not in fileB
> with one item per line for each.
>
> grep -Fvxf fileB fileA
>
> Really useful for finding kernel sysctl setting changes between large
> systems. Thousand line files are ms times.
>
> On Sat, Nov 9, 2024, 10:09 AM Charles Shapiro via Ale <ale at ale.org> wrote:
>
>> Learned this off mastodon today.
>>
>> **
>>
>> Here's an interesting Bash pattern I just used for the first time.
>>
>> some-command <<<"$(< some/file)" >some/file
>>
>> It reads all of some/file into memory before writing it to some-command's
>> stdin. This lets some-command's stdout be redirected to some/file without
>> the usual problems of reading/writing from the same file.
>>
>> **
>>
>>
>> H/T to @trs at metasocial.com <trs at metasocial.com>
>>
>>
>> -- CHS
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-- 
Pete Hardie
--------
Better Living Through Bitmaps
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