local GPG_ENV=$HOME/.gnupg/gpg-agent.env
  
  function start_agent_nossh {
      eval $(/usr/bin/env gpg-agent --quiet --daemon --write-env-file ${GPG_ENV} 2> /dev/null)
      chmod 600 ${GPG_ENV}
      export GPG_AGENT_INFO
  }
  
  function start_agent_withssh {
      eval $(/usr/bin/env gpg-agent --quiet --daemon --enable-ssh-support --write-env-file ${GPG_ENV} 2> /dev/null)
      chmod 600 ${GPG_ENV}
      export GPG_AGENT_INFO
      export SSH_AUTH_SOCK
      export SSH_AGENT_PID
  }
  
  # check if another agent is running
  if ! gpg-connect-agent --quiet /bye > /dev/null 2> /dev/null; then
      # source settings of old agent, if applicable
      if [ -f "${GPG_ENV}" ]; then
          . ${GPG_ENV} > /dev/null
          export GPG_AGENT_INFO
          export SSH_AUTH_SOCK
          export SSH_AGENT_PID
      fi
  
      # check again if another agent is running using the newly sourced settings
      if ! gpg-connect-agent --quiet /bye > /dev/null 2> /dev/null; then
          # check for existing ssh-agent
          if ssh-add -l > /dev/null 2> /dev/null; then
              # ssh-agent running, start gpg-agent without ssh support
              start_agent_nossh;
          else
              # otherwise start gpg-agent with ssh support
              start_agent_withssh;
          fi
      fi
  fi
  
  GPG_TTY=$(tty)
  export GPG_TTY