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NNTP-Posting-Date: Sun, 17 Nov 2024 04:59:41 +0000
Subject: Re: The joy of pipes
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Date: Sat, 16 Nov 2024 23:59:41 -0500
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On 11/16/24 5:31 AM, Richard Kettlewell wrote:
> Louis Krupp <lkrupp@invalid.pssw.com.invalid> writes:
>> On 11/15/2024 12:49 AM, 186282@ud0s4.net wrote:
>>
>>   On 11/14/24 9:05 PM, Lawrence D'Oliveiro wrote:
>>
>>   On Thu, 14 Nov 2024 16:09:07 -0800, John Ames wrote:
>>
>>   (I think it was a topic shift to applications of *nix pipes...?)
>>
>>   Oh shelly boy, the pipes, the pipes are calling ...
>>
>>     Pipes are good.
>>
>>     But, really, they're just temp files the parent
>>     process can access.
>>
>> Pipes *could* be implemented with temporary disk files, at least to an
>> extent, but as far as I can tell, they're not.
> 
> “Temporary files the parent can access” is not a good model for a couple
> of reasons:
> 
> * The semantics are different. Bytes read from a regular file are still
>    there to be read again if you rewind the file; bytes read from a pipe
>    are gone. Empty/full files behave differently to empty/full pipes.
> 
> * Temporary regular files can already be accessed by other processes by
>    name, by file descriptor inheritance, or file descriptor passing.


   Didn't say temp disk files were necessarily SUPERIOR, just
   that they CAN do most of the stuff pipes are used for and
   in an easier user/code-friendly fashion. SIZE is almost
   unlimited too.

   Anyway, I'd made some TCP/UDP servers but the parent needed
   to know the status of the children in a little more detail
   than just a tiny return code - might want to terminate the
   child if it'd been idle for awhile, might want to know how
   much bandwidth was being used, might want to pick a good
   time to do some maint routines, might want to know WHO the
   connections were from. Pipes were the (relatively) easy
   'C'-approved method and did the job very well.

   So, for most, use pipes. Python and FPC also do pipes.
   They're INTENDED for inter-process communications after
   all so generally GO that way.

   The Bi-Di server was the most fun ... think a "chat" app
   but with the potential for more than just text - closer
   to 'remote terminal'/SSH. ALMOST slipped into re-creating
   an FTP app until I realized where it was going. Too much
   enthusiasm. Commented-out the remote root system call
   function  :-)

   Amazing how LITTLE code is required for such things.
   Even the pre-threaded version (max cap) wasn't huge
   at all (albeit the hardest to 'hold in yer head' as
   to how it worked). Base examples in several langs easily
   found on the net - just build-on as necessary and
   then party on.