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        Tue, 30 Aug 2016 09:46:04 -0700 (PDT)
Date: Tue, 30 Aug 2016 17:46:01 +0100
From: Stephane Chazelas <stephane.chazelas@gmail.com>
To: Peter Stephenson <p.stephenson@samsung.com>
Cc: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: [PATCHv2] [bug] $SHLVL decremented for the last command of a
 subshell
Message-ID: <20160830164601.GA50437@chaz.gmail.com>
Mail-Followup-To: Peter Stephenson <p.stephenson@samsung.com>,
	Zsh hackers list <zsh-workers@zsh.org>
References: <20160822061723.GA7308@chaz.gmail.com>
 <20160829155156.GB17700@chaz.gmail.com>
 <160829185505.ZM8699@torch.brasslantern.com>
 <20160830124426.GA15615@chaz.gmail.com>
 <20160830140457.74d9d32d@pwslap01u.europe.root.pri>
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User-Agent: Mutt/1.5.21 (2010-09-15)

2016-08-30 14:04:57 +0100, Peter Stephenson:
[...]
> This is probably fine.  I've been dithering over cases where for
> consistency we might want to decrement SHLVL even in a subshell because
> we're exec'ing for some other reason (so would need to do it at the last
> minute before exiting if the exec is faked), but I suspect this is too
> obscure to be worth special treatment.
[...]

Note that zsh is currently correctly decrementing in

zsh -c '(printenv SHLVL)'

Where zsh optimises out the fork(s).

ksh93 seems to never decrease $SHLVL even in:

$ env SHLVL=1 ksh93 -c 'exec printenv SHLVL'
2

bash only optimises out the fork in the

bash -c 'single command'

case and gets it wrong:

$ env SHLVL=1  bash -c 'printenv SHLVL'
2
$ env SHLVL=1  bash -c 'exec printenv SHLVL'
1

tcsh doesn't opimise out any fork AFAICT.

Other shells don't seem to support $SHLVL.

-- 
Stephane