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Re: background processes (was HOW2 capture time of power-failure?)

Cross-posted to 2 groups.

Followups directed to: comp.os.linux.misc, comp.sys.raspberry-pi

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In article <m2tdmr$hi8$1@dont-email.me>, Joe Beanfish <joebeanfish@nospam.duh> wrote: 

> On Thu, 30 Oct 2014 08:32:11 +0000, not.socialnetwork wrote:
> > But I want to also test/confirm the general method, for apps which don't
> > have the special facilities of ogg123, that you were able to use.
> > 
> > I need to read-up on 'starting/stopping background/foreground'
> > processes,
> > after I've cleared some other chaos here.
> 
> Use "&" to start something in the background.
> Use "$!" to get the pid of the last background process started.
> Use "wait" to wait for a (or all) background process(es) to finish.
> Use "kill" to stop a background process.
> Here's something to start playing with:
> 
> #!/bin/sh
> echo "foreground pid $$ starting"
> (echo "background started";sleep 5;echo "background finished") &
> bgpid=$!
> sleep 1
> # wait around for background process to finish before quitting
> #echo "waiting for background pid $bgpid"
> #wait $bgpid
> # stop background process before quitting
> echo "killing background pid $bgpid"
> kill $bgpid
> echo "foreground pid $$ finished"

--- Nice tutorial. Thanks.

I've spent quite some time trying to analyse your code.
The very 1st line [of linux syntax] is problematic for me:
 apparently the EVALUATION of <pid $$> [what ever that is]
 is embedded in the reporting of <pid $$>.
 
IMO <linux syntax> has too many hidden-hooks to catch you;
like special rules for the 17th Tuesday of a non-leap-year.

After the multics OS failed, from excess complexity, Unix was
a spoof-name, trying to emphasise simplicity.  
Later, the blokes who designed unix abandoned it, for a simpler
design: plan9.

IMO prose is not a suitable substitute notation for a musical-score.

Here's a more graphic notation. Time moves-left-to-right.
  [..(...).]..

timer starts = [  
play starts = ( 
play ends = )
timer detects that play ended and records time and then stops = ]

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HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-26 17:38 +0000
  Re: HOW2 capture time of power-failure? Ian Malcolm <See.My.Sig.for.email@totally.invalid> - 2014-10-26 18:26 +0000
    Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-27 18:10 +0000
      Re: HOW2 capture time of power-failure? Gordon Henderson <gordon+usenet@drogon.net> - 2014-10-27 18:29 +0000
        Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-28 21:26 +0000
      Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-10-28 04:56 +0000
        Re: HOW2 capture time of power-failure? Dom <domafp@blueyonder.co.uk> - 2014-10-28 06:29 +0000
          Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-10-28 06:41 +0000
            Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-29 00:12 +0000
  Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-10-26 19:23 +0000
    Re: HOW2 capture time of power-failure? spam-no-spam@Freeola.net.invalid (Windmill) - 2014-11-04 13:19 +0000
      Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-11-05 21:56 +0000
        Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-11-06 14:12 +0000
        Re: HOW2 capture time of power-failure? nba@users.sourceforge.net (Niels Baggesen) - 2014-11-06 16:15 +0100
          Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-11-06 16:00 +0000
        Re: HOW2 capture time of power-failure? spam-no-spam@Freeola.net.invalid (Windmill) - 2014-11-06 20:37 +0000
      Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-11-06 14:13 +0000
  Re: HOW2 capture time of power-failure? andrew@cucumber.demon.co.uk (Andrew Gabriel) - 2014-10-26 20:28 +0000
  Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-10-27 13:17 +0000
  Re: HOW2 capture time of power-failure? Jean-David Beyer <jeandavid8@verizon.net> - 2014-10-28 13:43 -0400
    Re: HOW2 capture time of power-failure? Ant <ant@zimage.comANT> - 2014-10-29 08:18 -0700
  Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-10-29 13:28 +0000
    Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-30 08:32 +0000
      background processes (was HOW2 capture time of power-failure?) Joe Beanfish <joebeanfish@nospam.duh> - 2014-10-30 13:16 +0000
        Re: background processes (was HOW2 capture time of power-failure?) not.socialnetwork@gmail.com - 2014-11-03 03:25 +0000
          Re: background processes (was HOW2 capture time of power-failure?) "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2014-11-02 23:34 -0500
          Re: background processes (was HOW2 capture time of power-failure?) William Unruh <unruh@invalid.ca> - 2014-11-03 08:25 +0000
          Re: background processes (was HOW2 capture time of power-failure?) Martin Gregorie <martin@address-in-sig.invalid> - 2014-11-03 12:56 +0000
            Re: background processes (was HOW2 capture time of power-failure?) not.socialnetwork@gmail.com - 2014-11-06 19:19 +0000
              Re: background processes (was HOW2 capture time of power-failure?) Martin Gregorie <martin@address-in-sig.invalid> - 2014-11-07 02:36 +0000
              Re: background processes (was HOW2 capture time of power-failure?) Joe Beanfish <joebeanfish@nospam.duh> - 2014-11-07 14:28 +0000
                Re: background processes (was HOW2 capture time of power-failure?) not.socialnetwork@gmail.com - 2014-11-08 03:32 +0000

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