Send commands from command line to a running Python script in Unix

Question

I want to build a script that can be controlled while running from another scripts. For example I want to run my script like this:

~: Server &

and be able to run one of it's functions like:

~: client func1

Upon my searches I find signal module that have something like I want, but it's signals are predefined and I can not send signals of my own.

I even though of a client/server implementation using a network framework but I think it's too much for the abilities that I want my script to have.

Thank you all.

Answer 1

If you are only trying to send commands one-directionally to a server, it is easier than you think, using Python's Sockets. The code samples are of course barebones in the sense that they do not do error handling, and do not call recv multiple times to make sure the message is complete. This is just to give you an idea of how few lines of code it takes to process commands.

Here is a server program that simply receives messages and prints to stdout. Note that we use threading so that the server can listen to multiple clients at once.

import socket
from threading import Thread


MAX_LENGTH = 4096

def handle(clientsocket):
  while 1:
    buf = clientsocket.recv(MAX_LENGTH)
    if buf == '': return #client terminated connection
    print buf

serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

PORT = 10000
HOST = '127.0.0.1'

serversocket.bind((HOST, PORT))
serversocket.listen(10)

while 1:
    #accept connections from outside
    (clientsocket, address) = serversocket.accept()

    ct = Thread(target=handle, args=(clientsocket,))
    ct.start()

Here is a client program that sends commands to it.

import socket
import sys


HOST = '127.0.0.1'
PORT = 10000
s = socket.socket()
s.connect((HOST, PORT))

while 1:
    msg = raw_input("Command To Send: ")
    if msg == "close":
       s.close()
       sys.exit(0)
    s.send(msg)

Answer 2

So you need to talk to a running process right? What about the idea of unix domain socket?

In your server you can build up a socket on a path of your unix file system, then talk to that socket in you client, like described in this link I googled:

http://pymotw.com/2/socket/uds.html