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From: Bart Schaefer <schaefer@brasslantern.com>
Message-Id: <151126175625.ZM22214@torch.brasslantern.com>
Date: Thu, 26 Nov 2015 17:56:25 -0800
In-Reply-To: <5657939E.7070106@eastlink.ca>
Comments: In reply to Ray Andrews <rayandrews@eastlink.ca>
        "Re: curiosity with here document." (Nov 26,  3:19pm)
References: <56575158.1070303@eastlink.ca>  <1330101448564591@web8j.yandex.ru> 
	<5657939E.7070106@eastlink.ca>
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To: zsh-users@zsh.org
Subject: Re: curiosity with here document.
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On Nov 26,  3:19pm, Ray Andrews wrote:
}
} lesson learned.

Except it's the wrong lesson!  What you *ought* to learn is, first, that
for purposes of determining the "truth value" (zero or nonzero return
status),

    if command1; command2; command3; then ...

is the same as

    function three_commands {
	command1; command2; command3
    }
    if three_commands; then ...

And second, that [[ ... ]] is just a command like any other command,
it's not magically connected to "if".  Further, ":" is also a command
like any other command.

And third, that a here-document is just the standard input of the
command it follows, so

    : <<END
    some stuff
    END

is (again for purposes of determining truth value) the same as

    :

and the colon command is "true" for purposes of if/while/until/etc.,
it has a return status of zero.  So what you've written is

    if [[ ... ]]; : ; then ...

and colon is true and is the last command before the "then", so the
true branch is taken.

The here-document itself has no true or false interpretation, and the
presence of the here-document is not what is causing "if" to behave
the way it does.