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Date: Thu, 16 Jun 2011 11:20:28 -0400
From: Andrew Tannenbaum <trb@domain.hid>
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Subject: Re: [Xenomai-help] rtcanrecv output line-buffering
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To: xenomai@xenomai.org

I was trying to use the Xenomai RT-Socket-CAN rtcanrecv in a Tcl/Tk 
script GUI wrapper.

rtcanrecv uses printf to stdout, and it line-buffers when attached to a 
tty, but it uses larger buffers (so it is unusable) when run from a 
script with no tty.

Tcl does stdio with pipes rather than ptys (that is, Tcl thinks it has 
no tty for stdio).  I think both bash and perl use ptys (and so don't 
have this problem).  I haven't done a more thorough survey, but that's 
not the point.

I think it would be nice to modify rtcanrecv so it can write stdout in 
line-buffered mode.  If you think this is a good idea, please either set 
line buffering with

     setvbuf(stdout, NULL, _IOLBF, 0);

at the top of src/utils/can/rtcanrecv.c:rt_task() or

     fflush(stdout);

after the printf("\n") at the bottom of rt_task(), or you could add a 
command line getopt option for line-buffering that would do one of the 
above.

-Andy