#!/bin/sh
# ssh-agent-persist - create or reuse an ssh-agent as needed
# Andrew Ho (andrew@zeuscat.com)
#
# Usage: eval `ssh-agent-persist`
# Stores state directory in ~/.ssh-agent/`hostname`
# Also see ssh-agent-kill to clear existing ssh-agent invocations
#
# See http://www.zeuscat.com/andrew/software/desktop_hacks/#ssh-agent-persist
# for some background information about how I use this script.

ME=`basename "$0"`
IDENTITY_FILES='id_rsa'    # Edit this to add keys, if necessary

if [ "x$HOME" = "x" ]; then
    echo "echo '$ME: could not determine home directory' 2>&1"
    exit 1
fi

SSH_AGENT_ROOT="$HOME/.ssh-agent"
if [ ! -d "$SSH_AGENT_ROOT" ]; then
    echo "echo '$ME: creating state directory $SSH_AGENT_ROOT' 2>&1"
    mkdir -p "$SSH_AGENT_ROOT"
    if [ ! -d "$SSH_AGENT_ROOT" ]; then
        echo "echo '$ME: could not create $SSH_AGENT_ROOT' 2>&1;"
        exit 1
    fi
fi
if [ ! -w "$SSH_AGENT_ROOT" ]; then
    echo "echo '$ME: state directory $SSH_AGENT_ROOT is not writeable' 2>&1;"
    exit 1
fi

HOSTNAME=`hostname`
if [ "x$HOSTNAME" = "x" ]; then
    echo "echo '$ME: could not determine hostname' 2>&1;"
    HOSTNAME=unknown
fi

filename="$SSH_AGENT_ROOT/$HOSTNAME"
if [ -f "$filename" ]; then
    eval `cat "$filename"`
    if [ "x$SSH_AUTH_SOCK" != "x" ] && [ -w "$SSH_AUTH_SOCK" ]; then
        echo "echo 'Re-using existing ssh-agent socket.';"
        cat "$filename"
    else
        echo "echo 'Replacing existing but invalid ssh-agent socket.';"
        rm "$filename"
        ssh-agent | grep '=' | tee "$filename"
        for f in $IDENTITY_FILES ; do
            echo "ssh-add '$HOME/.ssh/$f';"
        done
    fi
else
    echo "echo 'Creating new ssh-agent socket.';"
    ssh-agent | grep '=' | tee "$filename"
    for f in $IDENTITY_FILES ; do
        echo "ssh-add '$HOME/.ssh/$f';"
    done
fi

exit 0