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Subject: Re: Sv: Named pipes and multiple writers
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From: Ken Brown via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Ken Brown <kbrown AT cornell DOT edu>
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On 3/26/2020 12:03 PM, Norton Allen wrote:
> On 3/26/2020 11:11 AM, Ken Brown via Cygwin wrote:
>>
>> BTW, I've been working on adding support for multiple readers.  I expect to 
>> have a first cut ready within a week or two.  Would you have any use for 
>> that?  If so, I could revive the topic/fifo branch and push my patches there 
>> for you to test.
>>
> 
> Ken, what are the semantics for multiple readers? Do all readers see the same 
> data,  or is it first come first served or something else?

It's first come, first served.  If two readers attempt to read simultaneously, 
it's possible that one will get some of the available input and the other will 
get some more.

The only use case for multiple readers that I've come across of is Midnight 
Commander running under tcsh.  I didn't dig into the code enough to know why 
they do it, or why only under tcsh.  See

   https://sourceware.org/pipermail/cygwin/2019-December/243317.html

and

   https://cygwin.com/pipermail/cygwin-apps/2019-December/039777.html

That's what got me interested in this.  It would be nice to know if there are 
other use cases.

Ken
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