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From: Pancho <Pancho.Jones@proton.me>
Newsgroups: comp.os.linux.misc
Subject: Re: Are We Back to the "Wars" Now ?
Date: Sat, 14 Dec 2024 10:10:57 +0000
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On 12/14/24 08:06, Richard L. Hamilton wrote:
> In article <lNycnZghasCXPtP6nZ2dnZfqnPSdnZ2d@earthlink.com>,
> 	"186282@ud0s4.net" <186283@ud0s4.net> writes:
>> On 11/19/24 7:22 PM, Lawrence D'Oliveiro wrote:
>>> On Mon, 18 Nov 2024 01:20:53 -0500, 186282@ud0s4.net wrote:
>>>
>>>> Hey, if I feel the need to use files instead of 'pipes' then I WANT TO
>>>> USE FILES INSTEAD OF PIPES.
>>>
>>> Except ... you were trying to argue that there was no fundamental
>>> difference between pipes and files anyway. That you could somehow do
>>> everything you could do with pipes by using temporary files.
>>
>>     Yep.
>>
>>     But I *just may not WANT to*  :-)
>>
>>     Files DO have a hidden advantage - many largely
>>     dis-related programs can ACCESS them. This can
>>     give you stats, insight, 'intelligence'. Pipes
>>     are basically restricted to the original parent
>>     and children. Good reasons for that, sometimes,
>>     but not *always*.
> 
> Named pipes can allow communication between unrelated processes.
> 
> Using files means there has to be locking or some coordination, so
> that the receiver only reads the file when the contents are in a
> consistent state.

I don't really know, but I would be surprised if that were always true.

> Renaming a file (on the same filesystem, where it's
> not a copy and delete) is atomic, so if the file is created in one
> directory and moved to a parallel directory when complete, the
> receiving program can just grab it from there, perhaps after being
> signalled to wake up and scan the directory. That works somewhat
> efficiently even without modern locking or filesystem change
> notification mechanisms.
> 

I suspect you are mixing up sensible programming techniques for handling 
file concurrency, with the way things need to be. i.e. I think it is 
perfectly possible to have concurrent programs read and write to the 
same file, it is just that there might be a few gotchas. Whereas 
renaming is a very safe and simple technique, avoiding many potential 
problems.

> A file has the advantage that one can seek on it, which may simplify
> some things; for example if a header has a checksum over the following
> data, it's easier to seek back and fill that field in with its final
> value. Otherwise one may have to use a temporary file internally anyway.