Automating ssh-add private keys with a common password - bash

Question

I have searched but the solutions I found were only focused on using a single key file.
Suppose I have a set of private keys which require the same password (and that I am confortable with such a setup from a security perspective).
How could I go about making a bash script that reads a password from stdin and invokes ssh-add for each of the private keys using the same password?
I do not have -p available for ssh-add.
I am trying to avoid writing the password to a file (even if temporary).
I came with this so far but I am unsure how to go or if this is possible:
#!/bin/bash
if [ $(ps ax | grep [s]sh-agent | wc -l) -gt 0 ] ; then
printf "> 'ssh-agent' is running.\n"
else
printf "> 'ssh-agent' needs to be running. Exiting.\n"
exit 0
fi
unset password
prompt="> Please input your password: "
while IFS= read -p "$prompt" -r -s -n 1 char
do
if [[ $char == $'\0' ]]
then
break
fi
prompt='*'
password+="$char"
done
printf "\n> Adding key files...\n"
## declare an array variable
declare -a arr=("key-1.ppk" "key-2.ppk" "key-3.ppk")
## now loop through the above array
for i in "${arr[#]}"
do
#echo "$i"
ssh-add "$i" < <(echo "$password")
done
Also tried the following to pass into stdin:
echo $password | ssh-add "$i"
I also thought about using this in the loop:
{
/usr/bin/expect << EOF
spawn ssh-add $HOME/.ssh/$i
send "$password\r"
expect eof
EOF
}
But then it would ask me to input a password for each individual key, defeating the purpose of automation.
Unless there is a way for a single spawn ssh-add to receive one single password via expect (only one prompt) and add more than one key with it?

Answer 1

If you have same password for all the keys then you can pass multiple keys to ssh-add and it prompts for password only once and adds all those keys to the ssh-agent.
eg:
$> arr=("id_ecdsa" "new_test_key")
$> ssh-add ${arr[#]}
Enter passphrase for id_ecdsa:
Identity added: id_ecdsa (test_user#host_test)
Identity added: new_test_key (test_user#host_test)
$> ssh-add -l
256 SHA256:urYhdMK9UZyLl+p8cC7ehdImYfvsmtJFtQmESWoczmM test_user#host_test (ECDSA)
256 SHA256:53obuQkRzLGW5iUJdmFPNvSK1quUSlCi4gbQkKsJinY test_user#host_test (ECDSA)

Answer 2

Password can be passed via environment variable :
#!/usr/bin/env bash
read password
ssh_askpass=$HOME/.ssh_askpass
echo 'echo "$password"' > $ssh_askpass; chmod 700 $ssh_askpass
ppk=key-1.ppk
export password
SSH_ASKPASS="$ssh_askpass" ssh-add $ppk < /dev/null
rm -f "$ssh_askpass"