Re: Change in indirect expansion behavior from 4.4 to 5.0

[Chet Ramey]

On 9/30/20 12:28 AM, Jason Miller wrote:
> Gentoo linux, GNU bash, version 5.0.18(1)-release (x86_64-pc-linux-gnu)
> 
> On the above vesion of bash, the following script will not run the echo 
> command
> and print an error.  On bash 4.4 it appears to  treat the ${!foo} the same as
> expanding an unset variable and thus outputs "bar":
> 
>   unset foo
>   echo ${!foo} bar

This is the result of

https://lists.gnu.org/archive/html/bug-bash/2016-11/msg00123.html

I explained the reasoning in

https://lists.gnu.org/archive/html/bug-bash/2016-11/msg00165.html

The basic idea is that indirect expansion is just a string substitution,
so indirecting an unset variable is the logically same thing as ${},
which is an expansion error.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/