source: vendor/bash/3.1-p17/examples/functions/array-to-string

#! /bin/bash

# Format: array_to_string vname_of_array vname_of_string separator
array_to_string()
{
        (( ($# < 2) || ($# > 3) )) && {
                 "$FUNCNAME: usage: $FUNCNAME arrayname stringname [separator]"
                return 2
        }

        local array=$1 string=$2
        ((3==$#)) && [[ $3 = ? ]] && local IFS="${3}${IFS}"
        eval $string="\"\${$array[*]}\""
        return 0
}