[Xenomai-help] Re: [Socketcan-users] Select on a RTCAN socket

[Wolfgang Grandegger <wg@domain.hid>]

Hi Daniel,

Daniel Schnell wrote:
> Hi,
> 
>  
> 
> I wanted to use select() on a socket to find out how many messages are 
> available. I have opened this socket to access the RTCAN sockets under 
> Xenomai. According to /usr/xenomai/lib/posix.wrappers select is not 
> “supported” by the realtime kernel. Accordingly it doesn’t work. If i 
> start the according task under SCHED_FIFO, the task simply hangs when 
> initiating select(), in SCHED_OTHER it is simply returning: bad file 
> descriptor.

select is not supported and cannot be used, indeed.

> Any ideas ? Is there any other way to find out, how many messages are 
> waiting ?

Select returns the sockets which have data but it does not tell you how 
many messages are waiting. You could use separate threads to read from 
sockets.

BTW: this mail is off-topic on the socketcan MLs.

Wolfgang.