Start ssh agent if it is not running

.bashrc

# If ssh-agent is not running, start it and add all keys

LINES=$(ps aux | grep ssh-agent | wc -l)
PPKDIR=~/.ssh/keys
PATTERN="\\.pub$"
if [ "2" -gt $LINES ] ; then
    ssh-agent -s > ~/.ssh-env-vars
    . ~/.ssh-env-vars

    for key in $(ls $PPKDIR) ; do
        # Add only private keys to ssh-agent
        if [[ ! $key =~ $PATTERN ]]; then
            ssh-add $PPKDIR/$key
        fi
    done
else
    . ~/.ssh-env-vars
fi