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From: Martin Schulte <gnu@schrader-schulte.de>
Newsgroups: gnu.bash.bug
Subject: Re: Two states of empty arrays
Date: Thu, 12 Dec 2019 22:34:52 +0100
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Approved: bug-bash@gnu.org
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To: =?ISO-8859-1?Q?L=E9a?= Gris <lea.gris@noiraude.net>
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Hello L=E9a!

L=E9a Gris <lea.gris@noiraude.net> wrote:
> I was trying to play the the -v test to detect when an array or
> associative array has been declared, not necessarily assigned entries
> key, values, to not error when Bash runs with -o nounset

Just for the curious: What is your attention here?

I think that most useful questions (Is there an element in the array? Is
there a value for a given key?) can be answered in a simpler way:

#!/bin/bash

set -o nounset

# From what I learned today it seems to be good practice to always
# assign and empty array to when declaring an associative array:
declare -A assoc=3D()

echo ${#assoc[@]} # Are there elements in it?

assoc[key1]=3Dval1
assoc[key2]=3D

for key in key1 key2 key3; do
  if [[ -n ${assoc[$key]+isset} ]]; then
    echo "Element for $key is set"
  else
    echo "No Element for $key"
  fi
done

Best regards,

Martin