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Re: Battery Powered Project

From Pancho <Pancho.Dontmaileme@outlook.com>
Newsgroups comp.sys.raspberry-pi
Subject Re: Battery Powered Project
Date 2021-01-18 13:20 +0000
Organization A noiseless patient Spider
Message-ID <ru41vs$tdp$1@dont-email.me> (permalink)
References (7 earlier) <rtvpka$3kh$3@dont-email.me> <rtvsuq$dbf$1@dont-email.me> <rtvu73$pb$1@dont-email.me> <ru1454$f7c$1@dont-email.me> <ru1hpk$qub$1@dont-email.me>

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On 17/01/2021 14:32, Martin Gregorie wrote:
> On Sun, 17 Jan 2021 10:39:32 +0000, Pancho wrote:
> 
>> However, I'm not yet convinced this is a sensible way of observing
>> events. I'm still undecided.
>>
> That depends: if the occurrence of events to be observed cause messages
> to be logged rather than being dealt with by the program that observes
> them, then watching a log for the occurrence might well be the best way
> to do it since this separates the observation from the consequent action,
> offering the possibility of more than one observing process being able to
> trigger the action. Where that action is irreversable, as it is in this
> case, that sounds like a good idea.
> 
> Of course, if the observer doesn't log anything, there's no reason to use
> a general purpose logfile - just write the observations to a file or
> pipeline that's accessable to the process that will execute the action:
> as this is Linux, you can use shared memory or a semaphore (if the
> programming language supports it) to signal that an actionable event has
> occurred. Shared memory, event queues and asynchronous i/o are all
> available in the C and Java standard function/class libraries but may not
> be in other languages.
> 
> OTOH if the required action is specific to the observer, i.e. doesn't
> affect anything outside the process(es) handling the data stream being
> observed, then simply deal with the observation inside the observing
> process.
> 
> 

Yeah, I'm not sure what you mean, the journal/logfile is the "subject", 
the "observer" logging isn't relevant.

FWIW I got this basic pattern to work.

--
  journalctl -f | awk -W interactive -- '/Specific Event/ { system( 
"/home/pi/SpecificEventHandler.sh") }'
--

Response appears to be ballpark of 30ms on a rPi3. Tested with:

date +%S-%N;logger "Specific Event"


And /home/pi/SpecificEventHandler.sh
--
#!/bin/bash

touch "awktest$(date +%H-%M-%S-%N)"

-

I'm not sure what awk interactive/buffering means. Without the "-W 
interactive" flag awk doesn't just buffer output, the system() call is 
delayed too. It's more like it is buffering input.

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Thread

Battery Powered Project Simple Simon <please.dontspa@me.com> - 2021-01-12 12:14 +0000
  Re: Battery Powered Project Chris Green <cl@isbd.net> - 2021-01-12 12:40 +0000
    Re: Battery Powered Project Simple Simon <please.dontspa@me.com> - 2021-01-12 12:50 +0000
      Re: Battery Powered Project "A. Dumas" <alexandre@dumas.fr.invalid> - 2021-01-12 15:15 +0100
      Re: Battery Powered Project Theo <theom+news@chiark.greenend.org.uk> - 2021-01-12 21:43 +0000
        Re: Battery Powered Project Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2021-01-13 09:40 +0000
        Re: Battery Powered Project Jim H <invalid@invalid.invalid> - 2021-01-13 18:02 +0000
        Re: Battery Powered Project Joe <joe@jretrading.com> - 2021-01-13 22:04 +0000
          Re: Battery Powered Project Theo <theom+news@chiark.greenend.org.uk> - 2021-01-13 23:37 +0000
            Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-14 00:43 +0000
            Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 03:59 +0000
            Re: Battery Powered Project Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-14 10:18 +0000
              Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 11:04 +0000
                Re: Battery Powered Project Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-14 11:46 +0000
                Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 12:21 +0000
                Re: Battery Powered Project Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-14 12:38 +0000
                Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-14 14:17 +0000
                Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 14:28 +0000
                Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-16 20:09 +0000
                Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-17 07:19 +0000
                Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-17 15:57 +0000
                Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-18 07:05 +0000
                Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-18 14:14 +0000
                Re: Battery Powered Project John Aldridge <jpsa@cantab.net> - 2021-01-17 17:52 +0000
              Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-14 12:56 +0000
              Re: Battery Powered Project Theo <theom+news@chiark.greenend.org.uk> - 2021-01-14 13:46 +0000
                Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 14:26 +0000
          Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 03:46 +0000
            Re: Battery Powered Project Folderol <general@musically.me.uk> - 2021-01-14 09:23 +0000
              Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 11:04 +0000
                Re: Battery Powered Project Folderol <general@musically.me.uk> - 2021-01-14 17:48 +0000
            Re: Battery Powered Project Jim H <invalid@invalid.invalid> - 2021-01-18 17:07 +0000
              Re: Battery Powered Project Joe <joe@jretrading.com> - 2021-01-18 20:33 +0000
                Re: Battery Powered Project Jim H <invalid@invalid.invalid> - 2021-01-21 20:36 +0000
  Battery Powered Project nospam.Vincent.Coen@f1.n250.z2.binkp.net (Vincent Coen) - 2021-01-12 14:35 +1300
  Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-12 16:40 +0000
    Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-13 13:56 +0000
      Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-13 15:12 +0000
        Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-16 12:24 +0000
          Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-16 17:53 +0000
            Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-16 20:39 +0000
              Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-16 22:33 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-16 23:30 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-16 23:52 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-17 10:39 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-17 14:32 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-18 13:20 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-18 13:41 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-18 14:02 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-18 15:15 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-19 13:46 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-19 15:24 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-19 15:34 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-19 16:21 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-19 17:18 +0000
                Re: Battery Powered Project Richard Kettlewell <invalid@invalid.invalid> - 2021-01-19 19:31 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-20 10:12 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-19 22:15 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-20 10:03 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 10:49 +0000
                Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-20 11:29 +0000
                Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 12:18 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 13:02 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-20 15:49 +0000
                Re: Battery Powered Project Richard Kettlewell <invalid@invalid.invalid> - 2021-01-20 16:54 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 17:19 +0000
                Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-21 10:24 +0000
                Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 12:18 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 13:18 +0000
                Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-20 14:14 +0000
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 14:51 +0000
                Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 14:45 +0000
                Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 14:44 +0000
                Re: Battery Powered Project Richard Kettlewell <invalid@invalid.invalid> - 2021-01-20 15:07 +0000
                Re: Battery Powered Project "A. Dumas" <alexandre@dumas.fr.invalid> - 2021-01-20 16:38 +0100
                Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-20 15:45 +0000
                Re: Battery Powered Project druck <news@druck.org.uk> - 2021-01-21 10:07 +0000
                Re: Battery Powered Project "A. Dumas" <alexandre@dumas.fr.invalid> - 2021-01-21 12:30 +0100
                Re: Battery Powered Project druck <news@druck.org.uk> - 2021-01-21 13:09 +0000
                Re: Battery Powered Project Anssi Saari <as@sci.fi> - 2021-01-22 10:08 +0200
                Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-22 10:29 +0000
                Re: Battery Powered Project Chris Green <cl@isbd.net> - 2021-01-22 10:25 +0000
                Re: Battery Powered Project Kees Nuyt <k.nuyt@nospam.demon.nl> - 2021-01-19 17:03 +0100
                Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-17 01:09 +0000
            Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-17 11:48 +0000
              Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-17 12:11 +0000
              Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-17 14:43 +0000
            Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-17 11:52 +0000
              Re: Battery Powered Project Andy Burns <usenet@andyburns.uk> - 2021-01-17 13:53 +0000

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