paramiko non blocking example

paramiko_runner.py

import sys
import paramiko
import os
import select
import getpass
import time

rpi = {
    "username": getpass.getuser(),
    "hostname": "hostname.of.server.here"
}

command = "cd /path/to/folder/ && python test_worker.py"
ssh = paramiko.SSHClient()
ssh.load_system_host_keys()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(**rpi)
ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command(command)

def worker(stdout, stderr):

    # Wait for the command to terminate
    print("Status of worker is {}".format(stdout.channel.exit_status_ready()))
    while not stdout.channel.exit_status_ready():
        time.sleep(1)
        print("Status of worker is {}".format(stdout.channel.exit_status_ready()))
        if stdout.channel.recv_ready():
            # Only print data if there is data to read in the channel
            print("Worker stdout.channel.recv_ready: {}".format(stdout.channel.recv_ready()))
            rl, wl, xl = select.select([stdout.channel], [], [], 0.0)
            if len(rl) > 0:
                # Print data from stdout
                print("Output: {}".format(stdout.channel.recv(1024).decode("utf-8")))



print("Reading output from master")
worker(ssh_stdout, ssh_stderr)
print("Finished reading output from master")

test_worker.py

import time
import sys

i = 0

while True:
    time.sleep(5)
    i = i + 5
    print("At time {}".format(i))
    if i > 15:
        sys.exit(0)

This is the output of running the code.

$ python paramiko_runner.py                                                                                                                                                                                                                    
Reading output from master
Worker function printer
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is False
Status of worker is True
Worker stdout.channel.recv_ready: True
Output: At time 5
At time 10
At time 15
At time 20

Finished reading output from master

I was expecting the "Output" to be printed in real time, instead of when the process ends.

Because "Python’s standard out is buffered.” , you have to flush the print output:
print("At time {}".format(i), flush = True)

Thanks for the input! I will try that!

I have a question, if these code is non-blocking example, when you invoke a shell and use it with send() a recv() instead of exec_command and stdout, is the shell that I have generated a blocking socket or a non-blocking socket? I'm very lost right now.