Re: [gentoo-dev] multiprocessing.eclass: doing parallel work in bash

[Zac Medico]

On 06/02/2012 04:47 PM, Brian Harring wrote:
> On Sat, Jun 02, 2012 at 03:50:06PM -0700, Zac Medico wrote:
>> On 06/02/2012 02:31 PM, Micha?? G??rny wrote:
>>> On Sat, 2 Jun 2012 15:54:03 -0400
>>> Mike Frysinger <vapier@g.o> wrote:
>>>
>>>> # @FUNCTION: redirect_alloc_fd
>>>> # @USAGE: <var> <file> [redirection]
>>>> # @DESCRIPTION:
>>>
>>> (...and a lot of code)
>>>
>>> I may be wrong but wouldn't it be simpler to just stick with a named
>>> pipe here? Well, at first glance you wouldn't be able to read exactly
>>> one result at a time but is it actually useful?
>>
>> I'm pretty sure that the pipe has remain constantly open in read mode
>> (which can only be done by assigning it a file descriptor). Otherwise,
>> there's a race condition that can occur, where a write is lost because
>> it's written just before the reader closes the pipe.
>
> There isn't a race; write side, it'll block once it exceeds pipe buf
> size; read side, bash's read functionality is explicitly byte by byte
> reads to avoid consuming data it doesn't need.

I've created a little test case and it seems you're right that nothing
is lost.
-- 
Thanks,
Zac