#! /bin/sh

set -e
usage="Usage: $0 [-bc] [COMMAND [ARGS...]]"

### Parse options
case "${SHELL-/bin/sh}" in
  *csh*) style=csh;;
  *) style=sh;;
esac
force= chosen= commands=
while [ $# -gt 0 ]; do
  case "$1" in
    -h | --help) echo "$usage"; exit 0;;
    -c | --cshell | --tcsh) style=csh chosen=t;;
    -b | --bourne | --bash | --zsh) style=sh chosen=t;;
    -f | --force) force=t;;
    --) shift; break;;
    -*) echo >&2 "$usage"; exit 1;;
    *) break;;
  esac
  shift
done
[ $# -gt 0 ] && style=commands
case $chosen,$style in
  t,commands)
    echo >&2 "$0: output style and commands? you're odd"
    exit 1
    ;;
esac

### Should I start a new agent?
case "$force,$SSH_AUTH_SOCK" in
  t,* | ,)
    start=t
    ;;
  *)
    start=
    set +e; ssh-add -l >/dev/null 2>&1; rc=$?; set -e    
    [ $rc -ge 2 ] && start=t
    ;;
esac

### If so, do that
if [ "$start" ]; then
  hostname=${HOST-$(hostname)}
  user=${USER-${LOGNAME-$(whoami)}}
  dir=$TMPDIR/.ssh-agent.$hostname.$user socket=$dir/sock pid=$dir/pid
  mkdir -p -m700 "$dir"
  SSH_AUTH_SOCK=$socket; export SSH_AUTH_SOCK
  set +e; ssh-add -l >/dev/null 2>&1; rc=$?; set -e    
  if [ $rc -ge 2 ]; then
    if [ -f "$pid" ]; then
      kill $(cat "$pid") >/dev/null 2>&1 || :
    fi
    rm -f "$socket" "$pid"
    (cd /; exec ssh-agent -d -a "$socket" >/dev/null 2>&1)&
    echo $! >"$pid"
    SSH_AUTH_SOCK=$socket; export SSH_AUTH_SOCK
  fi
fi

### Run a program, or export the details
case $style in
  sh)
    echo "SSH_AUTH_SOCK='$SSH_AUTH_SOCK'; export SSH_AUTH_SOCK"
    ;;
  csh)
    echo "setenv SSH_AUTH_SOCK '$SSH_AUTH_SOCK'"
    ;;
  commands)
    exec "$@"
    ;;
esac