Re: reading all data from FIFO with 'dd' without blocking

[Assaf Gordon]

Hello,

On 11/19/2014 02:24 PM, Pádraig Brady wrote:
> On 19/11/14 00:40, Assaf Gordon wrote:
<...>

> > With the above script, 'dd' prints the following:
> >      dd: error reading ‘standard input’: Resource temporarily unavailable
>
> That error is fine in itself and is just dd indicating that there is no data 
> available.
> I.E. the shell may have read all the data from the fifo and is splitting it up 
> with
> the read builtin. So it would probably be better to avoid the read built in and 
> use
> a loop like:

<...>

> However dd's setting of O_NONBLOCK on the _shared_ descriptor is problematic
> as it persists across the invocation of dd:
>
> http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/dont-set-shared-file-descriptors-to-non-blocking-mode.html
>
> That's a very non obvious gotcha.
> I wonder should we have an [io]flag=block to allow resetting this in dd?


Thank you, that's a terrific FGA post.

I guess for simplicity I'll stay with the 1s delay.

- Assaf.