Start ssh-agent at startup on ubuntu

start_ssh_agent.sh

# typically you'd add this at the end of eg .bashrc

# setup ssh-agent
SSH_ENV=$HOME/.ssh/environment
   
# start the ssh-agent
function start_agent {
    echo "Initializing new SSH agent..."
    # spawn ssh-agent
    /usr/bin/ssh-agent | sed 's/^echo/#echo/' > "${SSH_ENV}"
    echo succeeded
    chmod 600 "${SSH_ENV}"
    . "${SSH_ENV}" > /dev/null
    /usr/bin/ssh-add
}
   
if [ -f "${SSH_ENV}" ]; then
     . "${SSH_ENV}" > /dev/null
     ps -ef | grep ${SSH_AGENT_PID} | grep ssh-agent$ > /dev/null || {
        start_agent;
    }
else
    start_agent;
fi

That will start a new agent for every single shell.
It will also never clean it up.

setup ssh-agent

SSH_ENV=$HOME/.ssh/environment

Do I need to have a ~/.ssh/environment file for this to work? I am on a cloud-based IDE called "Cloud 9" using ubuntu 20.04 (ide.cs50.io) and it doesn't have this file, but it does have /etc/environment if that helps.