Subject: Re: Setting termios VMIN > 0 and VTIME > 0 on non blocking file
To: =?UTF-8?Q?=c3=85ke_Rehnman?= <ake.rehnman@gmail.com>, cygwin@cygwin.com
References: <9e4c6428-59de-df07-9e33-44ba95d5497f@gmail.com>
 <5be321d9-10c2-0853-b716-2abd10a4db3a@SystematicSw.ab.ca>
 <5541b350-9992-a0cf-ca77-43a0df83c0a8@gmail.com>
From: Norton Allen <allen@huarp.harvard.edu>
Message-ID: <f9d8744b-9271-9cbe-d79e-6a61b837d94d@huarp.harvard.edu>
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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