Function to start an ssh agent or load a running one into the current environment

ssh-agent-start.sh

function ssh-agent-start()
{
    local agentfile=~/.ssh/agent
    if [[ -f $agentfile ]]
    then
        source $agentfile > /dev/null
        if ps -p "$SSH_AGENT_PID" > /dev/null
        then
            echo "Agent running with PID $SSH_AGENT_PID"
            return
        fi
    fi
    echo "Could not find running agent. Starting new..."
    ssh-agent > $agentfile
    source $agentfile > /dev/null
    echo "Agent running with PID $SSH_AGENT_PID"
    ssh-add
}