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From: Bart Schaefer <schaefer@brasslantern.com>
Message-Id: <160420235800.ZM15082@torch.brasslantern.com>
Date: Wed, 20 Apr 2016 23:58:00 -0700
In-Reply-To: <87zisneh10.fsf@student.uu.se>
Comments: In reply to Emanuel Berg <embe8573@student.uu.se>
        "Re: virtual files?" (Apr 21,  4:12am)
References: <8760vdrt5y.fsf@student.uu.se> 
	<CAB2RFrTTibd-8FLs5GoGbMiTS2Gk8L8CVq1gC5im_8LmF3F6Zw@mail.gmail.com> 
	<87zisneh10.fsf@student.uu.se>
X-Mailer: OpenZMail Classic (0.9.2 24April2005)
To: zsh-users@zsh.org
Subject: Re: virtual files?
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On Apr 21,  4:12am, Emanuel Berg wrote:
} 
} What is the colon in =(:) - an "anonymous function
} qualifier"?

The syntax =(command) runs command and captures its output in a temp
file, then substitutes the name of the temp file; the file itself is
removed as soon as the current command finishes.  So

    echo =(echo foo)

will print something like /tmp/zshhKNk2F and

    cat =(echo foo)

will print foo.

Thus

    () { cat $1 } =(echo foo)

also prints foo.  The ":" command is just a quick built-in no-op that
produces no output, so that the temporary file created by =(:) will
be empty.