On Mon, 16 May 2016 13:47:30 +0100, scott wrote:

> On my pi I'm running raspbian, and have a process running as root to
> read a pin on the GPIO (connected to a PIR). Only root can read the GPIO
> pins, but obviously I don't want large, complex programs running as root
> just because they need to read a pin on the GPIO.
> 
> What's the best way for this root process to "broadcast" to other
> (non-root) processes when that pin goes high? It will only happen at
> maximum frequency of about every 2 seconds, but any delay between the
> pin going high and the other processes seeing it should be minimal.
> 
> I did think about using a file, that was write permission only for root,
> but readable by everyone, that seems like a lot of overhead though (and
> what if root tries to write to it as someone else is reading it?). In
> Windows I might consider using a broadcast message with the PostMessage
> API function, is there something similar for Linux?

Sockets are fairly common, or you might look to see if the Raspbian 
kernel has "capabilities" functionality that would let you grant a non-
root user access to the GPIO pins.

Jim
-- 
"I learned long ago, never to wrestle with a pig. You get dirty, and 
besides, the pig likes it." - George Bernard Shaw

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