Date: Tue, 13 Jul 1999 20:15:17 +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: <199907131815.UAA12928@dorifer.heim3.tu-clausthal.de>
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Sheldon Hearn wrote in list.freebsd-hackers:
> On Tue, 13 Jul 1999 18:13:42 +0200, Oliver Fromme wrote:
>
> > Command substitution certainly has to spawn a subshell, even
> > for built-in commands, because otherwise you could modify
> > parent shell variables within command substitutions.
>
> But isn't that exactly what's happening here, where PWD is being tainted
> by the commands evaluated within the substitution?
Yes, I'd call that a bug which should be fixed.
The manpage clearly says:
"The shell expands the command substitution by executing
command in a subshell environment and replacing the command
substitution with the standard output of the command [...]"
Alternatively, the manpage could be "fixed". ;-)
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.
Therefore I think the right thing to do is to fix FreeBSD's
sh to always execute command substitutions in a subshell.
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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