ssh_attach is to be sourced from a .profile and connects your shell to previously running ssh-agents . think of it as a slightly functional keymanager for your ssh sessions . --timball

ssh_attach.sh

#!/bin/bash
#
# ssh_attach.sh
#
#   source this file in a .bashrc . 
#
#   something like : 
#
#   # interactive shell ??
#   if [ "$PS1" ]; then
#        # attaching to a already running ssh-agent
#        if [ -f "$HOME/lib/ssh_attach.sh" ]; then
#                source "$HOME/lib/ssh_attach.sh"
#        fi
#   fi
#
#   and this script will find running ssh-agent processes and attach to it
#
#   it also gives you a set of aliases that are useful 
#
# Fri Dec 28 11:02:08 EST 2012
#            --timball@sunlightfoundation.com
#
# $Id$
#

# some useful aliases
alias ssh\-off="eval \`ssh-agent -k\`"
alias ssh\-on="eval \`ssh-agent -s\` && ssh-add"

AGENT="ssh-agent"


hug_ssh () {
    # getting here means we know that ssh-agent is running
    # if multiple $AGENTS are running it'll only grab the oldest process (as dictated by tail)
    # that assumes that the 2nd (or higher) $AGENT processes have been created by the user for a purpose for a reason beyond this script

    # be sure we're only called once
    unset hug_ssh 

    # i guess bad things would happen if $AGENT is not unique in the process namespace
    SSH_AGENT_PID=$(ps -axcu $USER | grep -v grep | grep $AGENT | tail -n 1 | awk '{print $2}')

    # oh man this is ghetto and fragile ... must find best way to find the SSH_AUTH_SOCK
    case $(uname -s) in
        Darwin)
            SSH_AUTH_SOCK=$(lsof -p $SSH_AGENT_PID | grep --color=no -E $((SSH_AGENT_PID - 1))$ | awk '{print $NF}')
            ;;
        Linux)
            # when did lsof stop working in fucking linux ?
            SSH_AUTH_SOCK=SSH_AUTH_SOCK=$(ls -la /tmp/ssh-*/agent.$((SSH_AGENT_PID - 1)) | awk '{print $NF}')
            ;;
        *)
            SSH_AUTH_SOCK=$(lsof -p $SSH_AGENT_PID | grep --color=no -E $((SSH_AGENT_PID - 1))$ | awk '{print $NF}')
            ;;
    esac

    # maybe the subshell failed
    if [[ $? = 1 ]]
    then
        interactive_print_err "no socket to attach too !"
        # probably should kill the ssh-agent process too if we can't find the socket
        kill $SSH_AGENT_PID
        unset AGENT
        interactive_print "turn $AGENT on w/ 'ssh-on'"
        return 1
    fi

    export SSH_AGENT_PID SSH_AUTH_SOCK &> /dev/null
    interactive_print "$AGENT attached at $SSH_AGENT_PID $SSH_AUTH_SOCK"
    return 0
}


is_running () {
    # this tests that $1 is a process that $USER is running
    # doesn't test to see if $1 is running more than once just that at least one copy is running
    # use like this :
    # if [[ "$(is_running $AGENT)" = "0" ]]
    # then
    #   # good
    # else 
    #   # bad
    # fi

    if [ -z "$1" ]
    then
        interactive_print_err "bad juju . no program to test against"
    else 
        ps -xu $USER | grep -v grep | grep $1 &> /dev/null
        if [ $? = "0" ] 
        then
            # good
            echo 0
        else
            # bad
            echo 1
        fi

    fi
}


_interactive_print () {
    if [ ! -z "$PS1" ]
    then
        echo $@
    fi
}
interactive_print_err () {
    if [ ! -z "$PS1" ]
    then
        echo $@ >2
    fi
}
interactive_print () {
    # only print to screen if in interactive prompt 
    # but call it from the protected function

    if [ ! -z "$1" ]
    then
        _interactive_print $@
    fi
}


ssh_agent_attach () {
    # main function 
    # tests that ssh-agent is running 
    # if it is attach to previously running process ... 

    # be sure we're only called once
    unset ssh_agent_attach

    if [[ "$(is_running $AGENT)" = "0" ]]
    then
        # good
        hug_ssh
    else 
        # bad
        interactive_print "turn $AGENT on w/ 'ssh-on'"
    fi

    return 0
}


ssh_agent_attach 
unset interactive_print
unset _interactive_print
unset AGENT