Re: Documentation feedback: surprising behavior of null substitutes

From: Laurent Bercot <>
Date: Fri, 20 May 2016 17:50:22 +0200

On 20/05/2016 17:42, Max Ivanov wrote:
> Docs on 'importas' specify that missing env var without a default
> value would produce a "null arg", however nowhere else term "null arg"
> is used or described (including very important "el_substitute"
> document), which lead to a surprising result at least for me:
> ```
> emptyenv -p import -u VAR s6-echo ABC:${VAR}:XYZ 123
> ```
> prints just "123", instead of expected "ABC::XYZ 123"

  Documentation for the -D option to importas: "If envvar is undefined,
and this option is not given, substitute zero word for variable instead
of the empty word".

  But you're right, despite it being a natural consequence of the
substitution rules, it's not intuitive that a word that contains ${VAR}
is completely removed when VAR is undefined. I will add a note to the
importas documentation that clarifies this.

Received on Fri May 20 2016 - 15:50:22 UTC

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