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From: arisawa <arisawa@ar.aichi-u.ac.jp>
In-Reply-To: <81c18ae059da79eb550d650650fa88c4@india.com>
Date: Tue, 25 Nov 2014 17:30:17 +0900
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Message-Id: <DAFEF014-D6DE-4A57-BB09-DAF335018E5C@ar.aichi-u.ac.jp>
References: <81c18ae059da79eb550d650650fa88c4@india.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] rc: null list in concatenation
Topicbox-Message-UUID: 2e1366ee-ead9-11e9-9d60-3106f5b1d025


> 2014/11/25 15:56=E3=80=81trebol@india.com =E3=81=AE=E3=83=A1=E3=83=BC=E3=
=83=AB=EF=BC=9A
>=20
> a =3D `{ls file}^test; echo 'this part is not executed if file =
doesn''t exist'

probably your question is as follows:

maia% a =3D `{ls file}^test; echo 'this part is not executed if file =
doesn''t exist'
ls: file: 'file' directory entry not found
rc: null list in concatenation
maia%=20

on the other hand,

maia% ls file;  echo 'this part is not executed if file doesn''t exist'
ls: file: 'file' directory entry not found
this part is not executed if file doesn't exist
maia%=20

a similar  thing is:
maia% (aa bb)=3Daaaa; echo bbbb
rc: variable name not singleton!
maia%=20

perhaps this is a feature.
rc stops execution if there is an error in grammar.