Date: Wed, 14 Jul 1999 18:57:35 +0200 (CEST) From: Oliver Fromme <olli@dorifer.heim3.tu-clausthal.de> To: freebsd-hackers@FreeBSD.ORG Subject: Re: bin/12578: `` subshell taints PWD Message-ID: <199907141657.SAA20332@dorifer.heim3.tu-clausthal.de>
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Niall Smart wrote in list.freebsd-hackers:
>
> > I'm not sure if XPG4v2 requires command substitution to behave
> > like that. At least, both Solaris' and DEC UNIX... oops...
> > True64 UNIX do execute all command substitutions in a subshell
> > (`pwd` does not affect the surrounding shell), and both claim
> > XPG4 compliance.
>
> They only execute a subshell when they need to:
No, it _always_ spawns a subshell.
> $ echo $$ `echo $$`
> 14405 14405
> $ uname -a
> SunOS molotov.boi.ie 5.6 Generic_105181-05 sun4u sparc SUNW,Ultra-5_10
That doesn't prove anything, because $$ always contains the
PID of the "top-level" shell, as I explained in an earlier
mail. Try this one:
$ echo $$ `( /bin/echo $$ )`
14762 14762
I think you agree that a subshell is spawned in that case,
don't you? ;-)
Regards
Oliver
--
Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany
(Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de)
"In jedem Stück Kohle wartet ein Diamant auf seine Geburt"
(Terry Pratchett)
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