How to check whether monero-wallet-rpc is running?

If you know the port monero-wallet-rpc listens on, you can connect to that port to see whether something is listening. This is what the python RPC layer does.

From utils/python-rpc/console.py in the Monero tree:

  # check for open port
  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  s.settimeout(1)
  if s.connect_ex((host, port)) != 0:
    raise Exception('No wallet or daemon RPC on port ' + str(port))
  s.close()

You could run ps aux | grep monero-wallet-rpc to see if the process is running.