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Subject: Re: Setting termios VMIN > 0 and VTIME > 0 on non blocking file
To: =?UTF-8?Q?=c3=85ke_Rehnman?= <ake DOT rehnman AT gmail DOT com>, cygwin AT cygwin DOT com
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From: Norton Allen <allen AT huarp DOT harvard DOT edu>
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Date: Wed, 11 Mar 2020 21:08:03 -0400
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On 3/11/2020 9:04 PM, Åke Rehnman via Cygwin wrote:
>
> On 2020-03-11 22:55, Brian Inglis wrote:
>> VMIN > 0 || VTIME > 0 implies blocking; O_NONBLOCK implies SIGIO 
>> delivery; see:
>>     https://www.tldp.org/HOWTO/pdf/Serial-Programming-HOWTO.pdf
>>     https://www.cmrr.umn.edu/~strupp/serial.html
>>     https://en.wikibooks.org/wiki/Serial_Programming/termios
>>
>> also read the man pages carefully and *assume* nothing; functions 
>> should work
>> *exactly* as documented: there be dragons!
>>
> According to https://www.cmrr.umn.edu/~strupp/serial.html "*Timeouts 
> are ignored in canonical input mode or when the/NDELAY/option is set 
> on the file via/open/or/fcntl/."*
>
> This leads me to believe the current cygwin implementation is not 
> correct. Changing the VMIN and VTIME should have no effect on the 
> read() behavior if the file was opened with O_NOBLOCK.
> ** 


Correct me if I am wrong, but O_NDELAY is not the same as O_NONBLOCK

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