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From: Bart Schaefer <schaefer@brasslantern.com>
Message-Id: <150727091512.ZM6365@torch.brasslantern.com>
Date: Mon, 27 Jul 2015 09:15:12 -0700
In-Reply-To: <87lhe23psr.fsf@secretsauce.net>
Comments: In reply to Dima Kogan <dima@secretsauce.net>
        "zargs parallelization support blows up with |&" (Jul 27,  2:36am)
References: <87lhe23psr.fsf@secretsauce.net>
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To: Dima Kogan <dima@secretsauce.net>, zsh-workers@zsh.org
Subject: Re: zargs parallelization support blows up with |&
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On Jul 27,  2:36am, Dima Kogan wrote:
}
} [... when piping] stdout and
} stderr for some output, then ALL the processes are invoked at the same
} time, not just 2 at a time like I asked:
} 
}  zargs -P2 -i -l1 `seq 10` -- perl -e 'sleep 20' {} |& grep x
} 
} I don't know if this is a bug or an expected consequence of some
} internal implementation details, but this is a really nasty failure
} mode.

The problem is that when you append a pipe to the end, zargs ends up
as a subshell, and you can't do job control in a subshell (which you
would have seen if you weren't grepping stderr):

(eval):wait:1: can't manipulate jobs in subshell

The workaround for now is as follows:

Copy the zargs script file to somewhere in your $path, e.g. ~/bin/.

Edit the copy to add a #!/bin/zsh (or your local path) at the top,
and "chmod +x" the file.

Then either always run zargs as a script instead of an autoload, or
when you need to pipeline it, use "command zargs".  This is a little
less convenient because it loses access to interactively-defined
functions, but if you're zargs-ing another external command such as
perl it should work fine.