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Date:	Fri, 13 Feb 2015 00:51:02 +0300
From:	Andrey Repin <anrdaemon AT yandex DOT ru>
Reply-To:	cygwin AT cygwin DOT com
Message-ID:	<925263616.20150213005102@yandex.ru>
To:	Corinna Vinschen <cygwin AT cygwin DOT com>, cygwin AT cygwin DOT com
Subject:	Re: Writing to /dev/clipboard from multiple processes in Bash gives inconsistent behaviour
In-Reply-To:	<20150212170342.GB7818@calimero.vinschen.de>
References:	<20150212134550 DOT GC20741 AT dinwoodie DOT org> <20150212170342 DOT GB7818 AT calimero DOT vinschen DOT de>
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Greetings, Corinna Vinschen!

> On Feb 12 13:45, Adam Dinwoodie wrote:
>> I've spotted some slightly odd behaviour when writing things from
>> multiple processes to /dev/clipboard.
>> 
>> Easiest to show this with an example:
>> 
>>     for n in {1..10}; do echo $n; done >/dev/clipboard; cat /dev/clipboard
>> 
>> I expect this to print out the numbers 1–10 to the terminal.  Sometimes
>> it does, but sometimes it misses out some of the numbers at the end;
>> printing the digits 1–8, say, but no more.  Generally it gets to around
>> 7–9, but I've seen it managing to only get up to 3 on one occasion.

> I can't reproduce this.  First I tried this manually a couple of times,
> but then I created a loop:

>   for i in {1..1000}
>   do
>     echo > /dev/clipboard
>     for n in {1..10}; do echo $n; done > /dev/clipboard
>     grep -q 10 /dev/clipboard || cat /dev/clipboard
>   done

> and it didn't fail once.  I'm not sure what to do if I don't have a
> reproducible testcase...

Failed ~20 times for me. And the more, the more I run the test.
What is more curious, is if I modify your test to only print "1",

while true; do
  echo > /dev/clipboard
  for n in {1..10}; do echo $n; done > /dev/clipboard
  grep -q 10 /dev/clipboard || grep 1 /dev/clipboard
done

it sporadically print 10 !
And my mail client actively flashing "paste" buttons, when the script is
working in background. May be that's it.

This is more visible:
$ while true; do { i=$(( $i+1 )); echo > /dev/clipboard; for n in {1..10}; do echo $n; done > /dev/clipboard; grep -q 10 /dev/clipboard || { grep 10 /dev/clipboard && echo $i;};}; done;
10
3512
10
6543
10
9468
10
9936
10
12298


--
WBR,
Andrey Repin (anrdaemon AT yandex DOT ru) 12.02.2015, <23:56>

Sorry for my terrible english...

- Raw text -