Re: unsetting associative array executes commands

[Chet Ramey]

On 3/11/21 10:06 AM, Jason A. Donenfeld wrote:
> This behavior is quite surprising:

The idea is that array subscripts undergo a uniform set of expansions when
they're used, no matter the context. Builtins already undergo word 
expansions as part of command execution. The result is double expansion
in certain cases (there are more; this is a staple of discussion here on
the list).

You can use the `assoc_expand_once' shell option to reduce the number of
expansions; it would have prevented the behavior you observed here, for
instance. But it's not perfect, as many people on the list will tell you.

> $ declare -A blah
> $ blah['$(DOESNOTEXIST)']=broken
> $ for i in "${!blah[@]}"; do echo "$i"; done
> $(DOESNOTEXIST)
> $ for i in "${!blah[@]}"; do unset blah["$i"]; done
> bash: DOESNOTEXIST: command not found
> bash: unset: [$(DOESNOTEXIST)]: bad array subscript


$ cat x1
declare -A blah
blah['$(DOESNOTEXIST)']=broken
shopt -s assoc_expand_once
for i in "${!blah[@]}"; do unset blah["$i"]; done
declare -p blah
$ ../bash-5.1-patched/bash ./x1
declare -A blah=()


--
``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/