Re: How to do? Possible?

[Eric Blake]

On 07/25/2011 03:45 PM, Linda Walsh wrote:
> I mistyped that but it brings me to an interesting
> conundrum:
>
> GLOBAL="hi there"
> {foo=GLOBAL echo ${!foo}; }

This says:

evaluate ${!foo}, and pass that expansion to 'echo', with foo=GLOBAL in 
the environment of echo.  You are invoking behavior that POSIX leaves 
undefined (that is, bash is perfectly fine evaluating ${!foo} prior to 
assigning foo, but bash would also be okay if it assigned foo prior to 
evaluating ${!foo}.  Hence, you got no output.

> But:
> > { foo=GLOBAL;echo ${!foo}; }
> hi there

The extra ; forces the semantics.  Here, the assignment to foo is a 
different statement than the expansion of of ${!foo}.  And while ${!foo} 
is a bash extension, it still proves that this is a case where foo was 
assigned prior to its use.

> Weird...

Not if you think about it properly.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org