SSH agent mangement for .bashrc or .zshrc

.sshagentrc

# ==========================================
# SSH Agent Configuration
# ==========================================
# Only run this for interactive shells
if [[ $- == *i* ]]; then
  AGENT_ENV_FILE="${HOME}/.ssh/agent-env"

  start_agent() {
    echo "Starting new ssh-agent..."
    ssh-agent -s | sed 's/^echo/#echo/' > "$AGENT_ENV_FILE"
    chmod 600 "$AGENT_ENV_FILE"
    source "$AGENT_ENV_FILE" > /dev/null
    ssh-add ~/.ssh/id_ed25519
    ssh-add ~/.ssh/signing_ed25519
  }

  # Load existing connection details if they exist
  if [ -f "$AGENT_ENV_FILE" ]; then
    source "$AGENT_ENV_FILE" > /dev/null
  fi

  # Check if we are connected to a live agent, otherwise start one
  if ! ssh-add -l >/dev/null 2>&1; then
    start_agent
  fi
  
  # --- Cleanup function for when the shell exits ---
  cleanup_agent() {
    # Count how many pseudo-terminals (tabs/windows) are currently open for your user.
    # Linux uses 'pts/', macOS uses 'ttys'
    local active_terminals=$(ps -u "$USER" -o tty= | grep -E -c "^(pts/|ttys)")
    
    # If this is the last terminal closing (count is 1 or somehow less)
    if [ "$active_terminals" -le 1 ]; then
      # Kill the ssh-agent process
      if [ -n "$SSH_AGENT_PID" ]; then
        eval "$(ssh-agent -k)" > /dev/null 2>&1
      fi
      # Remove the environment file so a fresh one is created next time
      rm -f "$AGENT_ENV_FILE"
    fi
  }

  # Tell the shell to run the cleanup function right before it exits
  trap cleanup_agent EXIT
fi