Share an ssh-agent session among multiple shells on the same computer.

ssh-reclaim

#!/bin/sh
# $Id$
#
# Limitations: if $ssh_auth_sock exists and an ssh-agent is running
# which doesn't use it, ssh-reclaim will be tricked into thinking
# that they correspond. This will happen if the computer shuts down
# uncleanly.
#
# Possible workarounds:
# * Check the command line of ssh-agent to see if we started it
# * Check for ssh sockets in /tmp owned by $USER

# Colors
ESC=$(printf "\033")
YELLOW="$ESC[1;33;01m"
BLUE="$ESC[1;34;01m"
DEFAULT="$ESC[0m"

start_agent() {
    eval "$(ssh-agent -s -a "$ssh_auth_sock" &)" >/dev/null
    if [ -t 0 ]; then
        echo " ${BLUE}*${DEFAULT} New agent started (pid ${SSH_AGENT_PID})"
        echo
    fi
}

# Start ssh-agent
if [ -t 0 ]; then
    echo
    echo " ${BLUE}*${DEFAULT} Starting ssh-agent..."
fi
ssh_agent_pid=$(pgrep -u "$USER" ssh-agent | cut -d' ' -f1)
ssh_auth_sock=$HOME/.ssh/agent-auth-sock-$(uname -n)
if [ -z "$ssh_agent_pid" ]; then
    rm -f "$ssh_auth_sock"
    start_agent
else
    if [ -e "$ssh_auth_sock" ]; then
        if [ -t 0 ]; then
            echo " ${BLUE}*${DEFAULT} Agent found (pid $ssh_agent_pid)"
            echo
        fi
        export SSH_AUTH_SOCK=$ssh_auth_sock SSH_AGENT_PID=$ssh_agent_pid
    else
        if [ -t 0 ]; then
            echo " ${YELLOW}*${DEFAULT} Killing stale agent (pid $ssh_agent_pid)"
        fi
        pkill -u "$USER" ssh-agent
        start_agent
    fi
fi