Reuse existing ssh-agent or start a new one

reuse_agent.sh

# Reuse an existing ssh-agent on login, or create a new one. Append this to your .bashrc
# This version also handles the case where the agent exists but has no keys.


function agent() {
    GOT_AGENT=0
    DEFTEMP="/tmp"

    for FILE in $(find "${TMPDIR:-$DEFTEMP}/ssh-"* -type s -user ${LOGNAME} -name "agent.[0-9]*" 2>/dev/null)
    do
        SOCK_PID=${FILE##*.}

        typeset -i PID
        PID=${SOCK_PID}+1
        ps "${PID}" 2>/dev/null | grep -q "ssh-agent"
        if [ "$?" = "0" ]
        then
            SOCK_FILE=${FILE}
            export SSH_AUTH_SOCK=${SOCK_FILE}
            export SSH_AGENT_PID=${PID}
            ssh-add -l > /dev/null
            if [ $? != 2 ]
            then
                GOT_AGENT=1
                echo "Reused agent pid ${PID}"
                break
            else
                unset SSH_AGENT_PID SSH_AUTH_SOCK
            fi
        else
            echo "Skipping pid ${PID}"
        fi
    done

    if [ $GOT_AGENT = 0 ]
    then
        eval `ssh-agent`
    fi
}

agent