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Date: Tue, 13 Dec 2011 12:32:37 -0500
From: Anthony R Fletcher <arif@mail.nih.gov>
To: <zsh-users@zsh.org>
Subject: Re: wait for the next process to finish
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On 13 Dec 2011 at 11:04:44, Rory Mulvaney wrote:
> pids=( )
> R=( $RANDOM $RANDOM )
> echo $R
> coproc () { sleep $(( $R[1]/32767.0*20 )) ; echo $$ }
> pids+=$!
> # copy the coproc fd
> exec 3<&p
> coproc () { sleep $(( $R[2]/32767.0*20 )) ; echo $$ }
> pids+=$!  
> exec 4<&p
> zmodload zsh/zselect
> zselect -r 3 4
> echo $reply
> 
> Then one could parse $reply.
> 
> I don't know, maybe there's a much easier way to create file descriptors 
> for those processes?
> 
> -Rory

I was using this loop

  for f in *.txt
  do
	  what-ever-has-to-happen $f &
	  pwait 20
  done

where pwait is a function

  function pwait() {
          while [ $(jobs -rp | wc -l) -ge $1 ]
          do
		  # sleep 10
                  wait
          done
  }

(see http://superuser.com/questions/158165/parallel-shell-loops for one
example amongst many).

I was hoping that using "wait" would be better than using a "sleep 10".
But wait waits for them all and not just he last to finish. The nice
thing is that this is a small, easy loop and all the brains is in the
barrier function pwait. Sadly a sleep for 10 seconds is completely
arbitrary.

			Anthony.

-- 
Anthony R Fletcher        
  Room 2033, Building 12A,        http://dcb.cit.nih.gov/~arif
  National Institutes of Health,  arif@mail.nih.gov
  12A South Drive, Bethesda,      Phone: (+1) 301 402 1741.
  MD 20892-5624, USA.