如何使用python执行erlang命令

Question

I want to execute some erlang commands, the shell can be launched by some command :

/opt/myserver/bin/myserver remote_console

Above command will launch a shell where I can execute erlang commands. I want to do the same thing from my python script.

I tried to do this using subprocess, but that does not seem to have worked.

import shlex
from subprocess import Popen, PIPE

cmd = '/opt/myserver/bin/myserver remote_console'
proc = Popen(shlex.split(cmd), stdin=PIPE, stdout=PIPE, stderr=STDOUT)
er_cmd = web_api_handler:process_rfid(30001,<<“RC“>>,arg).
out = proc.communicate(input=er_cmd)

Above method executes the erlang command but it fails with some reason. However I'm able to execute the same command when shell is launched without using python subprocess.

I tried using proc.stdin.write() and then use proc.communicate() as well, that did not work as well.

Answer 1

Erlang is not a scripting language, it was not designed to be executed and just die. Erlang is for long living task, and in your example, a better way to communicate with your python code is to use all communication facilities delivered with Erlang.

Another issue you will encounter with your method is about race condition and probably unordered output from Erlang node. Erlang don't guaranty starting order of all processes.

The best way in this case is to use interoperability tools from Erlang. A tutorial is available from Erlang Official Documentation . C Nodes, Drivers and NIFs are written in C but you can easily use Ports to interconnect your python script and your erlang code.

Another possibility is to use local unix socket (available since release 20) and use it to communicate with your python script.

Answer 2

I think you need Erlang Script . But I don't recommend you this. I think you should do it as Mathieu Kerjouan said.

If you insist on doing what your said, please consider solution below:

1. Start your Erlang application as a daemon.
2. Use escript to communicate with your application by Erlang's rpc.
3. Control the escript in your python code.