VAR=VALUE some-command https://unix.stackexchange.com/a/264642 https://unix.stackexchange.com/a/458901

1.bash

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
shopt -s inherit_errexit

declare -a k
echo "IFS=$IFS"

IFS=',' k=( $(printf '1,2,3') )

echo ${#k[@]}
echo "IFS=$IFS"

2.bash

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
shopt -s inherit_errexit

declare -a k
echo "IFS=$IFS"

foo() {
  k=( $(printf '1,2,3') )
}

IFS=',' foo

echo ${#k[@]}
echo "IFS=$IFS"

3.bash

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
shopt -s inherit_errexit

echo "IFS=$IFS"

IFS=',' echo '1,2,3'

echo "IFS=$IFS"