Attach ssh-agent to multiple terminals

ssh.bash

#!/usr/bin/bash
windows() { [[ -n "$WINDIR" ]]; }

if ! windows; then
    lock="/tmp/.lock-sshbash"
    exec 3>$lock
    flock --timeout 300 3 || exit 1
fi

get-agents() {
    if windows; then
        tasklist //V | grep ssh-agent | grep $(whoami)
    else
        ps x | grep ssh-agent | grep -v grep
    fi
}
get-pid() {
    if windows; then
        awk '{print $2}'
    else
        awk '{print $1}'
    fi
}
kill-ssh-agent(){
    for pid in $(get-agents | get-pid)
    do
        if windows; then
            taskkill //F //PID $pid
        else
            kill $pid
        fi
    done
}
print-ssh-connection-info(){
    echo $SSH_AUTH_SOCK
    if windows;then
        echo Agent winpid $(ps | grep $SSH_AGENT_PID | grep -v grep | awk '{print $4}')
    fi
    echo Agent pid $SSH_AGENT_PID
    echo Active keys
    echo -----------
    ssh-add -l
}
connect-ssh-agent(){
    if [ -f ~/.ssh/agent.sh ]
    then
        debug_ "running agent.sh"
        . ~/.ssh/agent.sh 2>&1 >/dev/null
        #print-ssh-connection-info
    else
        debug_ "agent.sh doesn't exist"
        touch ~/.ssh/agent.sh
        #echo "Critical Error: ~/.ssh/agent.sh does not exist"
    fi
}
start-ssh-agent(){
    debug_ "start_ssh_agent arguments: '$@'"
    if [[ "$@" != '--keep' ]]
    then
        debug_ "killing existing agents"
        if [[ "$@" == '--silent' ]]
        then
            kill-ssh-agent &> /dev/null
        else
            kill-ssh-agent
        fi
    else
        debug_ "keeping existing agents"
    fi
    ssh-agent > ~/.ssh/agent.sh
    connect-ssh-agent #run it
    reformat-agentsh
}
reformat-agentsh(){
    Line1="SSH_AUTH_SOCK=$SSH_AUTH_SOCK; export SSH_AUTH_SOCK;"
    Line2="SSH_AGENT_PID=$SSH_AGENT_PID; export SSH_AGENT_PID;"
    if windows
    then
        export SSH_AGENT_WINPID=$(ps | grep $SSH_AGENT_PID | grep -v grep | awk '{print $4}')
        Line3="SSH_AGENT_WINPID=$SSH_AGENT_WINPID; export SSH_AGENT_WINPID;"
    fi
    Line4="echo Agent winpid $SSH_AGENT_WINPID;"
    Line5="echo Agent pid $SSH_AGENT_PID;"
    debug_ "$Line1\n$Line2\n$Line3\n$Line4\n$Line5\n"
    printf "$Line1\n$Line2\n$Line3\n$Line4\n$Line5\n" > ~/.ssh/agent.sh
}

debug_ "debug mode on"
if [ -z "$CYGWIN_SHELL" ] && [ -z "$MSYS_SHELL" ]
then
    sshcount=0
    # To ensure we connect across ttys and even if we didn't run it at the tty level
    # we need to check a number of things. (and that it works on windows)
    # Check:
    #   that there is at least one agent running
    #   that the running agent is referenced inside agent.sh
    # If it is not the agent referenced inside agent.sh the user may have multiple running
    for pid in $(get-agents | get-pid)
    do
        ((sshcount++))
    done
    debug_ "ssh-agent count: $sshcount"

    if ((sshcount == 0))
    then
        # Start agent
        debug_ "user has no ssh-agents open"
        start-ssh-agent --keep
                                     #--keep micro-optimization
    else
        # Connect to existing agent
        debug_ "attempting to connect to the ssh-agent referenced inside agent.sh"
        connect-ssh-agent 1> /dev/null
                                     #  we want to display the connection info at the end, so we save it
        if ssh-add -l 2>&1 | grep "Error" &> /dev/null
        then
            # Start agent after failed connection attempt
            debug_ "ssh agent not connected or started"
            start-ssh-agent 1> /dev/null
        elif windows
        then
            # Windows? this probably doesn't work
            debug_ "Okay, we are connected to an agent but let's check that it is the PID inside agent.sh"
            PID=0
            for pid in $(get-agents | get-pid)
            do
                if [[ $pid == $SSH_AGENT_WINPID ]]
                then
                    debug_ "PID from agent.sh is running"
                    PID=$pid
                    break
                fi
            done
            if ((PID == 0))
            then
                debug_ "Could not find PID from agent.sh"
                start-ssh-agent --keep 1> /dev/null
            fi
        fi
        print-ssh-connection-info
    fi
fi
if ! windows; then
    rm -rf $lock
    flock -u 3
fi
#unset -f get-agents
#unset -f get-pid

Works on Windows(git for windows bash) and Linux.

Uses functions from functions.bash
functions used:

• newlock
• releaselock
• blockon
• debug_ sort of.. usually it is disabled so..

Intended to be loaded in .bashrc to connect your terminal(s) to an existing ssh-agent's which must have been started by this script.

Adds functions for easy command line intervention.

• kill-ssh-agent (kills all you own)
• start-ssh-agent (starts an ssh-agent, also prepares and saves ~/.ssh/agent.sh for other terminals to use.)
• connect-ssh-agent (connects terminals to the most recent started ssh-agent [via start-ssh-agent])
• rewrite-agentsh intended for in script use. This is needed on windows to ensure future terminals can find the ssh-agent running

On windows the PID reported in the ssh-agent output will not match what the windows task manager sees, or process explorer. It will match what ps sees however, which also reports the WINPID.. so the script finds the WINPID via the PID and saves it to the ~/.ssh/agent.sh script, along with the other ssh-agent output.

I almost wrote an issue in the git for windows issue tracker, until I realized the PID was matching the ps outputted PID. It was quite concerning when ssh-agent wasn't detecting the correct PID. Then I realized bash was providing a PID and WINPID. I initially switched to just using the PID for bash, but had a bug pop up where it couldn't find the PID after having closed Cmder/ConEmu.