On Fri, 19 Feb 1999, Rahul Dhesi wrote:
> Many years ago I posted a shell script to Usenet in which I prepended a
> line with 'exec', in an attempt to avoid having a shell process hanging
> around doing a wait(). David Korn himself (of Korn shell fame)
> responded saying this was not necessary, as the shell would do exec()
> anyway.
>
> I check with trace() on a Sun and he seemed to be right. This was for
> the classic Bourne shell many years ago.
>
> But I just checked /bin/sh on 3.1-RELEASE with ktrace and the above does
> not seem to be true. I get drastically different traces for
>
> #! /bin/sh
> exec /bin/pwd
>
> and
>
> #! /bin/sh
> /bin/pwd
>
> Rahul
I know that the FreeBSD Bourne shell doesn't do this, nor does the PDKSH.
I checked and the copy of the AT&T Korn shell I have (for BSDi) does do what
David Korn says.
>
> > Date: Fri, 19 Feb 99 11:43:59 EST
> > From: Mikhail Teterin <m...@misha.cisco.com>
> > To: curr...@freebsd.org
> > Message-Id: <199902191644.laa08...@misha.cisco.com>
> > Subject: sh(1) -- exec vs. fork
> > Reply-To: m...@aldan.algebra.com
>
> > I just finished going through a couple of crontabs prepending the
> > command-lines with ``exec'', when it hit me.
> >
> > Can shell itself recognize, there will be no more commands and just
> > proceed to exec without forking? What would this break?
> ...
>
>
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