forking ssh using python paramiko

Question

I am using the python module Paramiko to ssh to a linux box and execute two C programs. Program1 generates a signal on a DAQ device on a trigger. It waits for the trigger and terminates in 5 seconds. Program2 generates the trigger.

Here is my Python class:

class test:
    server = "localhost"
    username = "root"
    password = "12345"
    def ssh (self, cmd = ""):
            ssh = paramiko.SSHClient()
            ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
            ssh.connect(self.server,username=self.username,password=self.password)
            stdin, stdout, stderr = ssh.exec_command(cmd)
            result = stdout.read().splitlines()
            if len(result)!= 0:
                return result
            else:
                return -1

test.ssh("program1")
test.ssh("program2")

The problem is that program2 is being executed after program1 has been already terminated, so it doesn't generate anything. Is there a way I can run program2 faster than program1 is done? I have tried

test.ssh("program1 &")
test.ssh("program2") 

but to no avail. If I run these programs manually in two terminal shells, then it works fine. Any thoughts?

Answer 1

Can use threading or multiprocessing to execute the both the programs in different sessions

import multiprocessing

input = ["program1","program2"]   

for i in range(2):
    p = mutiprocessing.Process(target=test.ssh,args=(input[i],))
    p.start()
    processlist.append(p)

for p in processlist:
    p.join()

Answer 2

You could try running them in the same SSH session: test.ssh("program1 & program2") . This way you wouldn't be paying twice for all the set-up and tear-down that you do test.ssh .