Path: csiph.com!goblin1!goblin.stu.neva.ru!usenet.stanford.edu!not-for-mail
From: felix <felix@f-hauri.ch>
Newsgroups: gnu.bash.bug
Subject: Re: Command substitution
Date: Wed, 3 Jun 2020 08:38:50 +0200
Lines: 88
Approved: bug-bash@gnu.org
Message-ID: <mailman.1033.1591166340.2541.bug-bash@gnu.org>
References: <87mu5kgbxu.fsf@hobgoblin.ariadne.com> <20200603063850.GH8205@medium.hauri>
NNTP-Posting-Host: lists.gnu.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
X-Trace: usenet.stanford.edu 1591166340 13899 209.51.188.17 (3 Jun 2020 06:39:00 GMT)
X-Complaints-To: action@cs.stanford.edu
To: bug-bash@gnu.org
Envelope-to: bug-bash@gnu.org
Content-Disposition: inline
In-Reply-To: <87mu5kgbxu.fsf@hobgoblin.ariadne.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Received-SPF: none client-ip=212.74.161.16; envelope-from=felix@f-hauri.ch; helo=smtp.f-hauri.ch
X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/03 02:38:52
X-ACL-Warn: Detected OS   = Linux 2.2.x-3.x [generic] [fuzzy]
X-Spam_score_int: -18
X-Spam_score: -1.9
X-Spam_bar: -
X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, KHOP_DYNAMIC=0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN
X-Spam_action: no action
X-BeenThere: bug-bash@gnu.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: Bug reports for the GNU Bourne Again SHell <bug-bash.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/bug-bash>, <mailto:bug-bash-request@gnu.org?subject=unsubscribe>
List-Archive: <https://lists.gnu.org/archive/html/bug-bash>
List-Post: <mailto:bug-bash@gnu.org>
List-Help: <mailto:bug-bash-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/bug-bash>, <mailto:bug-bash-request@gnu.org?subject=subscribe>
X-Mailman-Original-Message-ID: <20200603063850.GH8205@medium.hauri>
X-Mailman-Original-References: <87mu5kgbxu.fsf@hobgoblin.ariadne.com>
Xref: csiph.com gnu.bash.bug:16357

Quoting is useless when assigning variable from ouptut of command or
another variable:

    $ foo=1 2 3 4 
    bash: 2: command not found

Ok. But

    $ foo=$(seq 1 3)
    $ declare -p foo
    declare -- foo="1
    2
    3"

    $ foo="$(seq 1 3)"
    $ declare -p foo
    declare -- foo="1
    2
    3"

No difference with or without double-quote.

    $ bar=$foo
    $ declare -p bar
    declare -- bar="1
    2
    3"

    $ bar="$foo"
    $ declare -p bar
    declare -- bar="1
    2
    3"

Again, double-quoting is useless.

But for commands:

    $ printf "<%s>\n" $foo
    <1>
    <2>
    <3>
    $ printf "<%s>\n" "$foo"
    <1
    2
    3>

Same than

    $ printf "<%s>\n" $(seq 1 3) 
    <1>
    <2>
    <3>
    $ printf "<%s>\n" "$(seq 1 3)"
    <1
    2
    3>

Unfortunely, I don't retrieve this behaviour in man page.

On Tue, Jun 02, 2020 at 09:44:45PM -0400, Dale R. Worley wrote:
> Naively, I expect that
> 
>     FOO="$( command2 )"
>     command1 $FOO
> 
> has the same effect as
> 
>     command1 $( command2 )
> 
> and
> 
>     FOO="$( command2 )"
>     command1 "$FOO"
> 
> has the same effect as
> 
>     command1 "$( command2 )"
> 
> Has anyone pushed the boundaries of this and can tell me whether there
> are gotchas?
> 
> Dale
> 

-- 
 Félix Hauri  -  <felix@f-hauri.ch>  -  http://www.f-hauri.ch