Date: Mon, 20 Jul 2009 11:02:43 +1000 From: Mark Andrews <marka@isc.org> To: Glen Barber <glen.j.barber@gmail.com> Cc: stable@freebsd.org Subject: Re: Shell execution ( [was] Re: Value of $? lost in the beginning of a function.) Message-ID: <200907200102.n6K12h1Y048534@drugs.dv.isc.org> In-Reply-To: Your message of "Sun, 19 Jul 2009 20:17:22 -0400." <4ad871310907191717g1ed90be7y92250f2addc38d43@mail.gmail.com> References: <4ad871310907191717g1ed90be7y92250f2addc38d43@mail.gmail.com>
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In message <4ad871310907191717g1ed90be7y92250f2addc38d43@mail.gmail.com>, Glen Barber writes: > Possibly off-topic... > > > 2009/7/19 Glen Barber <glen.j.barber@gmail.com>: > > 2009/7/19 Romain Tarti=E8re <romain@blogreen.org>: > >> Hi Glen, > >> > >> On Sun, Jul 19, 2009 at 04:32:28PM -0400, Glen Barber wrote: > >>> > % sh foo.sh > >>> > % zsh foo.sh > >>> > % bash foo.sh > >>> What happens if you replace '#!/bin/sh' with '#!/usr/local/bin/zsh' ? > >> > >> This is not related to my problem since I am not running the script > >> using ./foo.sh but directly using the proper shell. =A0sh just behaves > >> differently, that looks odd so I would like to know if it is a bug in sh > >> or if there is no specification for this and the behaviour depends of > >> the implementation of each shell, in which case I have to tweak the > >> script I am porting to avoid this construct (passing $? as an argument > >> for example). > >> > >> Romain > >> > > > > My understanding was this: > > > > If you specify 'sh foo.sh' at the shell, the script will be run in a > > /bin/sh shell, _unless_ you override the shell _in_ the script. > > > > Ie, 'sh foo.sh' containing '#!/bin/sh' being redundant, but 'zsh > > foo.sh' containing '#!/bin/sh' would execute using zsh. > > > > > > I meant to say in the last line: "'#!/bin/sh' would override the 'zsh' shel= > l." > > Can someone enlighten me if I am wrong about this? > > --=20 > Glen Barber > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" "#!" is used to define the interpretor when the file is exec'd. perl, AFAIK, is the only interpretor that will look at what is after the "#!" and modify it's behaviour. All other a interpretors (shells) treat "#!" as a comment. Some shells used to examine the executable about to be called and looked for "#!" and invoke the correct interpretor. This was how "#!" was supported before kernels has support for "#!". It was all done in userland. Mark -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@isc.org
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