Bash: convert comma seperated ips into array of ip

I am getting comma seperated IPs as a string in my application from terraform. I need to replace variable in a conf file with array of ips. Number ips can be anything. I have taken 2 as an example.

Script.sh:

#!/bin/bash
var_ips="10.10.10.177,10.10.10.181"

IFS=','
read -ra ip_array <<< "$var_ips"
form_hosts=()
for item in "${ip_array[@]}";do
     form_hosts+=("\"$item\"")
done 

sed -i "s/^hosts: \"from_terraform_hosts\"$/hosts: [${form_hosts[*]}]/g" host.conf

host.conf

hosts: "from_terraform_hosts"
//file truncated

Here i want entry in host.conf as

hosts: ["10.10.10.177","10.10.10.181"]

but i am getting

hosts: ["10.10.10.177" "10.10.10.181"]

Comma is missing when i substitute the values. Can anyone help to fix above issue.
The difference is due to below

echo [${form_hosts[*]}]
echo "[${form_hosts[*]}]"

Output

["10.10.10.177" "10.10.10.181"]
["10.10.10.177", "10.10.10.181"]

Here under double quotes only comma is coming but i cant use this way inside sed command.

>Solution :

You can do it with Bash’s parameter expansion, no arrays needed:

#!/bin/bash

var_ips="10.10.10.177,10.10.10.181"

sed -i "s/^hosts: \"from_terraform_hosts\"$/hosts: [\"${var_ips//,/\",\"}\"]/g" host.conf

${var_ips//,/\",\"} expands $var_ips but replaces commas with "," and the sed replacement wraps it in [" and "].

Note that this’ll only work as long as $var_ips doesn’t contain any ‘funny stuff’, e.g. spaces (they would end up inside the quotes) or regex-special characters (they would break the sed command).