Date: Sun, 22 Sep 2013 17:56:07 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Glen Barber <gjb@FreeBSD.org> Cc: FreeBSD Hackers <freebsd-hackers@FreeBSD.org>, freebsd-current <freebsd-current@FreeBSD.org> Subject: Re: The right way to invoke sh from a freebsd makefile? Message-ID: <1379894167.1197.126.camel@revolution.hippie.lan> In-Reply-To: <20130922234555.GE2336@glenbarber.us> References: <1379891905.1197.115.camel@revolution.hippie.lan> <20130922232710.GD2336@glenbarber.us> <1379893071.1197.119.camel@revolution.hippie.lan> <20130922234555.GE2336@glenbarber.us>
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On Sun, 2013-09-22 at 19:45 -0400, Glen Barber wrote:
> On Sun, Sep 22, 2013 at 05:37:51PM -0600, Ian Lepore wrote:
> > On Sun, 2013-09-22 at 19:27 -0400, Glen Barber wrote:
> > > On Sun, Sep 22, 2013 at 05:18:25PM -0600, Ian Lepore wrote:
> > > > What's the right way to launch the bourne shell from a makefile? I had
> > > > assumed the ${SHELL} variable would be set to "the right" copy
> > > > of /bin/sh (like maybe the one in tmp or legacy at various stages). It
> > > > appears that that's not the case, and ${SHELL} is whatever comes from
> > > > the environment, which can lead to using csh or bash or whatever.
> > > >
> > > > I see some of our makefiles use just a bare "sh" which seems reasonable
> > > > to me, but I don't want to glitch this in src/include/Makefile again.
> > > > The goal is to run a script in src/include/Makefile by launching sh with
> > > > the script name (as opposed to launching the script and letting the #!
> > > > do its thing, which doesn't work if the source dir is mounted noexec).
> > > >
> > >
> > > I think BUILDENV_SHELL is what you are looking for. For this specific
> > > case, I think instead of '#!/bin/sh', maybe '#!/usr/bin/env sh' may be
> > > preferable.
> > >
> > > Glen
> > >
> >
> > No, BUILDENV_SHELL is a special thing... it's used when you "make
> > buildenv" to chroot into a cross-build environment to work
> > interactively. I added that long ago because I can't live in a csh
> > shell (I mean, I can't do anything, I'm totally lost), and I wanted a
> > way to have "make buildenv" put me right into bash (of course, you have
> > to have bash in the chroot).
> >
>
> Ah, right. Thanks for the sanity check.
>
> > The flavor of hashbang to use shouldn't matter, since what I'm after
> > here is launching the shell to run the script without using the hashbang
> > mechanism.
> >
>
> You can hard-code /bin/sh directly, but what I was getting at with the
> '#!/usr/bin/env sh' is that the 'sh' interpreter of the build
> environment could be used (instead of /bin/sh directly). Then you don't
> need to worry about the path to sh(1).
>
> Glen
>
My point is that the #! isn't used at all in this case, it doesn't
matter what's there. Try this...
echo "echo foo" >/tmp/foo
sh /tmp/foo
Not only does it not need the hashbang, the script doesn't even have to
be executable when you launch sh and name a script on the command line,
which is just what's needed to run a script from a directory mounted
with the noexec flag.
-- Ian
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