ssh-agent.sh

#!/usr/bin/env bash

export SSH_ENV="$HOME/.ssh/agent-macbook-pro"
export AGENTALIVE=0

# Start an ssh-agent and write out the details to $SSH_ENV
function agent_start() {
  # Check to see if this is an interactive session. If so then echo stuff. If not, don't.
  if [[ $- =~ "i" ]]; then
    echo -n " [i] Initializing a new SSH agent..."
  fi
  umask 177
  /usr/bin/ssh-agent | sed 's/^echo/#echo/' > "${SSH_ENV}"
  source "${SSH_ENV}" > /dev/null
  echo done
}

# Reconnect to the last ssh-agent that was loaded
function agent_restore_or_start() {
  if [[ -f $SSH_ENV ]]; then
    source $SSH_ENV
    agent_check_alive
  else
    agent_start
    agent_check_alive
  fi
}

function agent_check_alive() {
  # Check to see if there are any ssh-agents running on the PID
  # that we loaded from the agent file.
  if [[ $SSH_AGENT_PID ]]; then
    AGENTALIVE=$(ps wwaux | grep [s]sh-agent | grep -c $SSH_AGENT_PID)
    if [[ $AGENTALIVE -ne 1 ]]
    then
      start_agent
      AGENTALIVE=$(ps wwaux | grep [s]sh-agent | grep -c $SSH_AGENT_PID)
    fi
  else
      start_agent
      AGENTALIVE=$(ps wwaux | grep [s]sh-agent | grep -c $SSH_AGENT_PID)
  fi

  # If the agent is alive, check to see if there are any loaded keys
  if [[ $AGENTALIVE -eq 1 ]]; then
    no_key_loaded=$(ssh-add -l | grep -c "The agent has no identities.")
    if [[ $no_key_loaded -eq 1 ]]; then
      # Check to see if this is an interactive session. If so then echo stuff. If not, don't.
      if [[ $- =~ "i" ]]; then
        echo " [!] No loaded SSH keys"
      fi
      if [[ -e ~/.ssh/id_rsa ]] || [[ -e ~/.ssh/id_ed25519 ]]; then
        ssh-add
      fi
    else
      # Check to see if this is an interactive session. If so then echo stuff. If not, don't.
      if [[ $- =~ "i" ]]; then
        var=$(ssh-add -l | awk '{print $3}' | sed -e 's,.*/,,g' | xargs)
        echo " [x] Loaded ssh keys: $var"
      fi
    fi
  fi
}

agent_restore_or_start