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Date: Wed, 23 Aug 2006 19:07:46 +0200
From: Wolfgang Grandegger <wg@domain.hid>
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Subject: [Xenomai-help] Re: [Socketcan-users] Select on a RTCAN socket
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To: Daniel Schnell <danielsch@domain.hid>
Cc: Haukur Hafsteinsson <haukur@domain.hid>, xenomai-help <xenomai@xenomai.org>, socketcan-users@domain.hid

Hi Daniel,

Daniel Schnell wrote:
> Hi,
>=20
> =20
>=20
> I wanted to use select() on a socket to find out how many messages are=20
> available. I have opened this socket to access the RTCAN sockets under=20
> Xenomai. According to /usr/xenomai/lib/posix.wrappers select is not=20
> =93supported=94 by the realtime kernel. Accordingly it doesn=92t work. =
If i=20
> start the according task under SCHED_FIFO, the task simply hangs when=20
> initiating select(), in SCHED_OTHER it is simply returning: bad file=20
> descriptor.

select is not supported and cannot be used, indeed.

> Any ideas ? Is there any other way to find out, how many messages are=20
> waiting ?

Select returns the sockets which have data but it does not tell you how=20
many messages are waiting. You could use separate threads to read from=20
sockets.

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

Wolfgang.