On Sun, Dec 12, 2021 at 08:47:21PM +0100, l.bash...@scarydevilmonastery.net
wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -g -O2 -fstack-protector-strong -Wformat
> -Werror=format-security -Wall
> uname output: Linux h2 5.15.0-2-amd64 #1 SMP Debian 5.15.5-1 (2021-11-26)
> x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Bash Version: 5.1
> Patch Level: 12
> Release Status: release
>
> Description:
> making left square bracket char ([) part of the key into a hash causes
> unset to silently fail when trying to unset that specific hash item.
> The position of left square bracket char in the string used as key
> doesn't
> matter. unset also fails when the key is a single [ character.
> Please refer to the following script which attempts to demonstrate this
> quirk.
>
> Repeat-By:
>
> # diagnostic shows remains of hash after attempts to unset single item.
> show() { echo "$1, ${#a[@]} items in a: a['${!a[@]}']=${a['[foo]']}"; }
>
>
> # prepare test scenario
>
> declare -A a # make "a" a hash
> a['[foo]']="bar" # assign "bar" to item keyed [foo]
> show "good" # correctly output item, show correct
> item count
>
>
> # intention is to get rid of the item again, by unsetting the single item,
> not the whole array.
> # several ways of quoting are attempted here
>
> unset "a['[foo]']" # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> unset 'a["[foo]"]' # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> unset 'a[[foo]]' # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> unset "a[[foo]]" # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> unset "a[\[foo]]" # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> unset "a["\[foo]"]" # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> unset "a['['foo]]" # try to remove item
> show "wrong" # can still output item, item still
> counts
>
> a["[foo]"]="" # Best I can currently do
> show "set empty, item still counted" # item still there though contents are
> empty string.
Just to say this unsets the element correctly:
k='[foo]'
unset -v 'a["$k"]'
--
Andreas (Kusalananda) Kähäri
SciLifeLab, NBIS, ICM
Uppsala University, Sweden
.
