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Re: /bin/sh should set SHELL to /bin/sh

From: Dan Douglas
Subject: Re: /bin/sh should set SHELL to /bin/sh
Date: Fri, 14 Jul 2017 20:29:29 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.0

On 07/14/2017 03:13 PM, Greg Wooledge wrote:
> On Sat, Jul 15, 2017 at 02:59:41AM +0700, Robert Elz wrote:
>> IMO, if SHELL gets unset (it is usually initialised by login, or its
>> equivalent), it should simply stay unset, and not be set to anything,
>> until some user (or script) decides to set it again.
> wooledg:~$ unset SHELL
> wooledg:~$ bash -c 'echo "$SHELL"'
> /bin/bash
> wooledg:~$ ksh -c 'echo "$SHELL"'
> /bin/sh
> wooledg:~$ zsh -c 'echo "$SHELL"'
> wooledg:~$ tcsh -c 'echo "$SHELL"'
> SHELL: Undefined variable.
> Looks like there's not much agreement here.

Good thing is bash doesn't export SHELL if it wasn't already exported,
and most shells seem to preserve the value of SHELL exported by some
parent. I see mksh sets -x if SHELL was previously unset... I suppose
that might cause a problem in some scenario (but probably not).

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